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2009, 28 (S1): -0 doi:
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RESEARCH ON MECHANISM AND APPLICATION TO FLOOR HEAVE CONTROL OF DEEP GATEWAY

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2009, 28 (S1): -2593 doi:
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The rock mass structure of surrounding rocks with non linear large-scale deformation in deep entry of coal mines is studied. A new method is proposed to control floor heave considering the effect of the roof，side and corner on the floor in design. Based on the micro-fabric test，theoretic analysis，numerical simulation and in-situ test，mechanism of controlling floor heave with bolt-net-anchor coupling support technology is discussed. With the anchor wire at key location mobilizing the strength of deep rock，the compression force passing from top of the breaking rocks over the wall is lessened；with the intensity strengthened and deformation reduced，the length constrained by side for the floor heave is shortened；with the rigid bolt and corner grouting，the pressure from side decreased and the shear resistance at corner is improved. Therefore，floor heave is controlled effectively. The theory is applied to control the stability of deep coal roadway in Jiahe coal mine and in-situ measurement shows that the large-scale deformation and floor heave are successfully controlled.

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EXPERIMENTAL STUDY OF INFLUENCE OF LOADING RATE ON KAISER EFFECT OF DIFFERENT LITHOLOGICAL ROCKS

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2009, 28 (S1): -2599 doi:
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Different loading rates on rock samples may lead to considerable differences among the cumulative AE hit-stress curves. Kaiser stress values of sandstone，gritstone and mudstone increase with relatively faster loading rate，while for brittle rock-like limestone，loading rate has hardly any influence on Kaiser effect. Hence，a more in-depth analysis of the influence of loading rate on Kaiser effect of different lithological rock is very necessary. On one hand，all cracks in rock samples，regardless of their sizes，slip and propagate when loading rate is relatively smaller，which leads to a clearer acoustic emission signal. As a result，a smaller stress value is achieved. On the other hand，only larger cracks slip and propagate when loading rate is speeding up，which results in larger stress value. As for different lithological rocks，distinct loading rates are needed during the tests. In addition，the research shows that Kaiser effect point of the core below 2 500 m appears after its collapse point，which demonstrates that the measurement of Kaiser effect under confining pressure is needed in order to simulate formation situation to achieve corresponding stress value. The results of the test are applied to oilfield tests. The experimental results in laboratory test are in largely accordance with those in oilfield. It provides theoretical basis and reference for testing in-situ stress by Kaiser effect laboratory tests.

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STUDY ON SHEAR CREEP AND ROUGHNESS EFFECT
ON HARD DISCONTINUITIES OF MARBLE

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2009, 28 (S1): -2605 doi:
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[PDF 217 KB] (981)

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The rock masses of underground cavern of Jinping II Hydropower Station are enriched in abundant joints. A shear creep experimental program is carried out on hard discontinuities of marble mass using double-axis creep apparatus. Surface of hard discontinuities of marble masses is measured，and roughness of the surface is described by average roughness angle. The variation law of shear displacement of marble with the time is analyzed under different roughness. Test results show that instantaneous deformation of rock sample with large roughness angle is less than that of rock sample with small roughness angle rock sample. In addition，decay and steady creep occur when stress level is relatively low，however，when shear stress level reaches a certain level，rock specimen fails rapidly within a short period of time，and acceleration creep doesnt occur in the process of shear rheology experiment. Consequently，a standard linear shear creep model of marble is identified by shear creep experimental data，and model parameters of marble specimen are gained. The comparison between fitting curve and test curve shows that the standard linear shear creep model is reasonable. Finally，the variation law of average roughness angle of marble specimen and shear creep model parameters is analyzed.

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NUMERICAL ANALYSIS OF ENDANGER OF CRACK IN STANDARDIZATION DIKE OF YELLOW RIVER IN DONGMING OF SHANDONG PROVINCE

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2009, 28 (S1): -2612 doi:
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When dike reinforcement with silt was applied in Yellow River，cracks appeared in the first stage project in Henan and Shandong Province. Because of the particularity for the dike reinforcement with silt，there was no quantitative result of the effect of crack on safety of dike，and safety features of dike were not clarified under the work of crack so that it would be restricted to prepare treatment and counter plan of contingency. When dilapidation or crack occurred in dike，the safety status was influenced by factors including status of crack，water level，rainfall，characteristic of soil and so on. Taking the Dongming dike-section of Yellow River in Shandong Province as an example，endanger of crack on safety of dike was analyzed. It shows that the deeper the depth of crack is，the lower the safe of dike is，and the safety of status of dike becomes abominable with rainfall. Moreover，the damage degree of crack of dike is closely correlated with the characteristic of soil，and the chance of accident is proportional to the rainfall duration，intension of rainfall，depth of crack，decreasing velocity of water level of the dike in nearby river. The results could be applicable as reference in flood control emergency and the maintenance and reinforcement of the dikes.

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HYBRID MESH-FREE FINITE VOLUME DIFFERENCE METHOD FOR ELASTOPLASTIC PROBLEMS

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2009, 28 (S1): -2620 doi:
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To improve the precision of stresses with the mesh-free method，the stresses as well as displacements are interpolated independently. The whole domain is divided into boundary-domain and inside-domain. For the nodes on the boundary，the mesh-free finite volume method is used to establish the discrete equations. For the other nodes inside the domain，the mesh-free finite difference method is employed to discretize the gradients of stress node by node. Under the hypothesis of the small deformation，the hybrid mesh-free finite volume difference method for elasto-plastic analyses is proposed based on the incremental constitutive equations. The course of tunnel excavation is stimulated. Numerical examples show that the proposed incremental hybrid mesh-free finite volumetric difference method has high precision and efficiency，moreover it is of some practical value.

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STUDY OF EFFECT OF NONLINEAR NORMAL DEFORMATION JOINT ON ELECTROMAGNETIC EMISSION(EME) INTENSITY INDUCED BY STRESS WAVE

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2009, 28 (S1): -2629 doi:
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In order to study the effect of the nonlinear joint on intensity of the electromagnetic emission(EME) during propagation process，the relationship between induced EME and incident stress wave was presented based on piezoelectric effect mechanism. According to the obtained relationship and the resolution of transmitted and reflected coefficients when the normal incident P-wave propagated to the nonlinear normal deformation joint，the relational expression between the intensity variation of EME and parameters of joint was obtained. And the effects of parameters such as joint deformation and incident frequency of wave on the intensity variation of EME were investigated. It is shown that the intensity of the EME induced by stress wave was the highest in the explosion-center and attenuated with the propagation distance；the intensity of the EME increased with the joint deformation；the higher frequency EME attenuated faster than the lower frequency signals.

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INFLUENCE OF MOISTURE CONTENTS ON MECHANICAL PROPERTIES OF SEDIMENTARY ROCK AND ITS BURSTING POTENTIAL

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2009, 28 (S1): -2637 doi:
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The mechanical properties of coal series sedimentary rock and its bursting potential in different moisture contents are studied，and the models and correlations between moisture content and bursting potential are established. The controlling mechanism of moisture content of mechanical properties of sedimentary rock and its bursting potential is also revealed. It is shown that the uniaxial compressive strength and the values of elastic modulus decrease with the increase of moisture content，whose influence degree differs from lithology，and the decreasing rates are controlled by lithology. The rock after peak strength of stress-strain curve represents brittleness and shear failure has obvious strain softening behavior in the condition of dried or with small moisture content. With increase of moisture content，the brittleness index modified(BIM) of rock increases gradually，while elastic deformation exponential decreases and the stored elastic strain energy decreases sharply in the process of stress；however，the consumed permanent plastic deformation energy increases relatively，which means that the bursting potential of rock decreases significantly with the increase of moisture content.

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EXPERIMENTAL STUDY OF INFLUENCES OF CONFINING PRESSURES AND GROUND WATER ON RESIDUAL STRENGTH AND POST-PEAK VOLUMETRIC CHANGE OF SOFT ROCK

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2009, 28 (S1): -2644 doi:
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[PDF 209 KB] (1007)

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The post-peak mechanical behaviors of black macker widely distributed in Baozhen tunnel are discussed by a series of triaxial compressive tests under different saturated times，and research on changing laws of rock residual strengths and post-peak volumetric strain under different confining pressures and saturated times is carried out. In addition，the mechanism and features of confining pressure，saturation time acting on remnant strength are researched. Finally，the timing of carrying out secondary lining is analyzed.

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STUDY OF STRENGTH PROPERTIES OF EARTH-ROCK AGGREGATE BASED ON FRACTALS

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2009, 28 (S1): -2651 doi:
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Starting from nonlinear characteristics of earth-rock aggregate，fractal geometry theory was used to study earth-rock aggregate strength properties .The stress-strain relationship，strength parameter characteristics and peak strength were analyzed under different confining pressures and fractal dimensions of granularity using large-scale triaxial tests. Relationships among strength parameters，peak stress difference and fractal dimensions of granularity were also discussed. Test results indicate that stress-strain properties of earth-rock aggregate were similar to stress-strain curves of typical rock，and strength envelope under different fractal dimensions of granularity was linear approximately. The earth-rock aggregate with 1D fractal had the largest compact ability and shear strength，which belonged to optimal gradation earth-rock aggregate and the reason was analyzed as well.

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STUDY OF RELATIONSHIP BETWEEN ROCK MASS DEFORMATION AND PERMEABILITY EVOLVEMENT

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2009, 28 (S1): -2657 doi:
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STATISTICAL ANALYSIS OF TIME EFFECTS ON SURROUNDING ROCK OF NATM HIGHWAY TUNNEL

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2009, 28 (S1): -2662 doi:
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[PDF 172 KB] (1183)

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Based on field monitoring data of more than fifty two-lane highway tunnels，the data of convergence displacements and vault settlements were analyzed through statistical method. The deformation characteristics of different surrounding rock levels from II to V with time were also studied，and the stable time was proposed for surrounding rock from excavation to stabilization. The relationship between levels and stable time of surrounding rock was defined，which provided basis for evaluation of surrounding rock and construction time of secondary lining.

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SLOPE DEFORMATION CHARACTER ANALYSIS BASED ON MONITORING RESULTS OF MULTIPLE MULTI-POINT BOREHOLE EXTENSOMETER

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2009, 28 (S1): -2667 doi:
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[PDF 242 KB] (861)

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Based on engineering practice，the displacement-time，displacement-depth and deformation-speed curves are adopted to analyze monitoring results from points in time and space. In order to obtain a comprehensive analysis of the slope deformation，the monitoring results of instruments installed in different places are compared. Generally speaking，the character of excavating slope deformation becomes larger with the decrease of the altitude. However，the character of deformation of soft rock is different. In fact，the impacting factors of deformation are various in practical projects；therefore，it is necessary to understand deformation mechanism under various factors by means of geological information combining with construction progress and patrol result in order to estimate the stability state of slope.

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RESEARCH ON SPREAD CHARACTERISTICS OF MICRO-SEISMIC WAVE IN MINE STRATA

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2009, 28 (S1): -2674 doi:
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[PDF 593 KB] (1290)

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In the sublevel caving longwall face 8103 of Tashan coal mine，an abnormal phenomenon that time of micro-seismic wave transmitting to bottom hole geophones far from the hypocenter was shorter than that to roof hole geophones near hypocenter. According to classical model of micro-seismic wave transmission，the energy consumption and transmitting time of micro-seismic wave induced by roof through separation layers and coal seam to bottom hole geophones must be larger. In order to explain the phenomenon，it was assumed that new hypocenter was formed at the interface between bottom floor and coal seam when micro-seismic waves induced by immediate roof or main roof passed through the entrance interface of coal seam and bottom vertically. Transmission direct assumption explained the phenomenon that remote point reached first on the basis of sufficient research on stress history and support effort，etc.. In-situ experiment of calibration blasting confirmed that obtained time difference according to the assumption was equal to true reach time difference approximately. So transmission direct assumption could be used in hypocenter localization and checking. It also could be used for improving location precision.

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SOLUTION TO MODEL TEST OF LAYERED FAILURE WITHIN ROCK MASS AROUND DEEP-BURIED TUNNEL

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2009, 28 (S1): -2680 doi:
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The model test on mechanism of layered failure within rock mass around deep-buried tunnel is re-analysed. At first，the fracture shape of surrounding rock mass is studied. The failure of the model medium has two patterns：tensile and shear. Stress field of surrounding rock mass is deduced using jagged rock mass model and ultimate strain failure criteria. By comparing with test results，the solution is proved to be correct. It is shown that the interval tension fracture would occur repeatedly under large axial compression stress，which forms the layered failure. The geometry of tension fracture tends to be round gradually. When a new tension fracture takes place，the model is equivalent to a tunnel with support. With the increment of tunnel radial，the supporting force increases rapidly，which makes the layered failure limited to a certain rangeal. The analytical method provides theoretical basis for studying rules of layered failure of rock mass around deep-buried tunnel under different conditions.

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THREEDIMENSIONAL FE REGRESSION ANALYSIS OF MULTIVARIATE GEOSTRESS FIELD OF WUSHAOLING TUNNEL

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2009, 28 (S1): -2687 doi:
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[PDF 871 KB] (1104)

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The initial geostress field of tunnel area is analyzed by 3D multivariate FE regression based on limited points of in-situ geostress measurement. Two large-scale 3D FE computational models are established. Then geostress including gravity，tectonic stress field for horizontal extrusion and shear in four cases are computed by with ANSYS. And the multivariate regression analysis is carried out by MEBA and MEBAC，which is an interface program connecting MEBA and ANSYS. It is emphasized on the analysis of complicated stress condition and macro description of stress field around Wushaoling tunnel，especially the stress condition in and around the faults F4，F5，F6 and F7. The results of macro geostress field indicate that the direction of principle stresses is N21.2°E，which forms separation angle of 38.2° to the tunnel axis. The tunnel lining in faults zone is extruded in longitudinal direction and stressed asymmetrically in horizontal direction. The values of the geostress are relatively large. The maximal vertical geostress is 32.10 MPa and the maximal geostress perpendicular to tunnel axis is 21.72 MPa. The results of macro geostress field are very important for dynamic design and construction.

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EXPERIMENTAL RESEARCH AND NUMERICAL SIMULATION OF ACOUSTIC EMISSION OF MEMORY EFFECT OF ROCK STRESS UNDER POINT LOAD

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2009, 28 (S1): -2695 doi:
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[PDF 329 KB] (909)

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Theoretical expression of memory effect of previous stress under point load is established based on damage mechanics of Kaiser effect in uniaxial compression. Fourteen specimens with different parameters of mechanical properties and different ratios of height to width are given to simulate memorizing ability of previous stresses in rock specimens under point load using software of RFPA2D(rock failure process analysis). The results show that the value of point load on specimens increases with the increase of previous stresses in rock specimens when acoustic emission occurs. In order to further verify the results obtained from numerical simulation，acoustic emission experiments of 5 specimens under loading and unloading of uniaxial compression and point loading are conducted. The experimental results agree well with those of numerical simulation. It provides a new method for the estimation and assessment of in-situ stress.

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SIMULATION OF FAULT MOVEMENT INDUCED RUPTURE PROCESS OF OVERLAYING SOIL OF BEDROCK

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2009, 28 (S1): -2703 doi:
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[PDF 178 KB] (901)

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Earthquake fault dislocation-induced ruptures of soil layers are simulated by finite element method. The study demonstrates soil rupture propagation and characteristics，and also proves the observed earthquake phenomenon that a ground surface rupture failure does not mean a penetrating rupture failure. The simulation results indicate that the soil rupture starts at interface between soil and bedrock and expands upward. Furthermore，one or two ruptures appear at ground surface and extend downward with the increase of fault dislocation，and the ruptures from bedrock and ground surface meet somewhere in soils so that a penetrating rupture from bedrock to ground surface occurs if fault dislocation is large enough. Three kinds of soil ruptures including buried rupture，non-penetrating ground surface rupture and penetrating soil rupture are presented in case of different fault dislocations and soil conditions. The obvious effects of soil thickness and properties on characteristics of soil rupture are revealed. The ground surface rupture belt is enlarged due to the increase of soil thickness if a ground surface rupture occurs，and the rupture angle is almost not affected by soil thickness and properties. The width of rupture belt of sands is smaller than that of clays，and the penetrating rupture occurs more easily for harder soil than for softer soils. In condition of reverse fault，the value of bedrock fault dislocation for initial ground surface rupture occurring is 80% or less than that for a penetrating rupture occurring，and the vertical value of bedrock fault dislocation for a penetrating rupture occurring is 5%less than that of soil thickness for soil layer with thickness less than 50 m.

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NONLINEAR CREEP CONSTITUTIVE MODEL OF BEDDED SALT ROCK

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2009, 28 (S1): -2708 doi:
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As for alternating layers of mudstone and salt rock，representative volume element(RVE) in the composite is established. Based on strain compatibility principle and micromechanical method，considering elastic behavior of mudstone interbeds，elastic and creep behavior of salt，an anisotropic incremental nonlinear composite creep constitutive model of bedded salt rock is derived；stress redistribution is analyzed during creep deformation of salt. The new model is introduced into finite element software ABAQUS. A simple bedded salt rock sample is modeled as case study to verify the composite model. The result agrees well with the experiment，so it is shown that the constitutive model can reflect mechanical behavior of bedded salt rock considering micro-strain compatibility. The model can be employed to analyze long-term stability of bedded salt rock cavern in the future.

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THEORETICAL ANALYSIS OF EFFECT OF ANOMALOUSLY LOW FRICTION ON ROCK MASS BASED ON SIMPLY SUPPORTED BEAM MODEL

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2009, 28 (S1): -2715 doi:
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[PDF 278 KB] (700)

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Based on theory of plasticity kinetics，simply supported beam model of effect of anomalously low friction on rock mass was established considering deep coal mining. Through theoretical deduce，analytical formulas of normal stress of contact interfaces between rock and roof in elastic stage and elastic-plasticity stage under dynamic load were both presented. The relationship curves between q/p， and t were analyzed. The variation rules of friction on contact interfaces in rock mass were obtained. The effect of anomalously low friction on rock mass was explained on the basis of plasticity kinetics. The results indicate that normal stress of contact interfaces between rock and roof in elastic stage and elastic-plasticity stage reduced sharply under dynamic load. And the reduction amplitudes were relatively large. It is shown that friction on the contact interfaces reduced，which presented obvious effect of friction disappearance. Therefore，the existence of effect of anomalously low friction on rock mass was proved. Comparing normal stress of contact interface on elastic stage with that on elastic-plasticity stage，reduction amplitude of the former was larger，which illustrated that effect of anomalously low friction on contact interface between rock and roof was easy to occur when the beam was in elastic stage.

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STUDY ON CLOSING LAW OF CRACK IN ROCK MASS UNDER COMPRESSION

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2009, 28 (S1): -2721 doi:
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[PDF 477 KB] (830)

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The theory on deformation of an open crack surface under compression is studied by methods of complex function and conformal transformation，and the deformation parameters of the crack surface are solved. Base on this theory，the geometric model for analysis of open crack closure is established. Through the geometric model，two conclusions are drawn as follows. First，the closing law of the open crack is obtained which agrees well with the general viewpoints of rock mechanics—an open crack exists either completely closed or completely opened under compressive loading in rock mass. Second，the criterion for a crack closure is defined which is expressed by the deformation parameters. Using this criterion，the critical closing stress of an open crack can be determined by a simple quadratic equation. Besides，this criterion is not influenced by the assumption of the loading patterns，and it can be applied under any compressive load，which extends the applied range of the traditional closing criteria of open crack. At the same time，it is very convenient because of its simple mathematical form and definite physical meanings of unknown parameters. Finally，both theoretic analysis using the above conclusions and the numerical simulation are used to analyze the closing process of the crack surface under various loading patterns，and the numerical results agree well with those of the theoretic ones，which proves the validity of the proposed conclusion.

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BACK ANALYSIS OF PERMEABILITY OF FRACTURED ROCK

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2009, 28 (S1): -2730 doi:
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The approximate relationship between connectivity ratio and connectivity coefficient of fractures in rock mass is proposed. The equivalent permeability tensor of rock mass，which has single set of fractures，is deduced. The finite element method to analyze single-hole directional water pressure test is established，and a series of numerical tests are carried out. The numerical test results are used as train samples for BP neural network. The trained BP neural network combined with the information of single-hole directional water pressure test forms the methodology for the back analysis of the equivalent permeability tensor. The reliability of the method is verified by engineering example.

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DETERMINATION AND APPLICATION OF MODULUS OF DEFORMATION OF ROCK MASSES BASED ON GSI SYSTEM

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2009, 28 (S1): -2736 doi:
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The deformation modulus of rock mass is an important input parameter in analyzing deformation，which should be determined by field tests. However，field tests are time consuming，expensive and the reliability is sometimes questionable. Based on data from in-situ measurements，E. Hoek proposed a new empirical formula for estimating values of deformation modulus of rock mass based on geological strength index(GSI). In order to provide more quantitative basis for evaluating GSI values，quantitative GSI system has been proposed by introducing measurable parameters with ratings or intervals which define structure and surface conditions of discontinuities. Especially，the methods to determine the parameter volumetric joint count(Jv) are studied in detail Finally，the proposed methods have been applied to practical projects and its rationality is further verified by comparing with field tests results.

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ANALYSIS OF FAILURE FEATURE OF BARRE GRANITE
UNDER DYNAMIC COMPRESSION

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2009, 28 (S1): -2743 doi:
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High strain rate uniaxial compressive loading tests on disk Barre granite(BG) samples were conducted by modified split Hopkinson pressure bar(SHPB) system with pulse shaping and momentum-trap technique. The samples were tested under X(intermediate P-wave velocity)，Y(lowest P-wave velocity)，and Z (highest P-wave velocity) directions. The dynamic stress equilibrium on both ends of the sample and constant strain rate was achieved during loading with help of pulse shaper(copper + rubber) technique. The momentum-trap technique was adopted to protect the sample from multi-loading by the incident bar. Corresponding to three loading levels，three damage levels of the rock samples were identified according to the extents of damage，namely，quaso-elastic，cracked，and fragmented samples. The damage assessment of recovered sample was investigated after cut to thin sections，and the microcrack increased with the loading rate. The stress-strain curves of samples at different strain rates(70，100，130 s－1) under three directions were obtained. The correlation between the failure modes and shape of the stress-strain curves was discussed. The maximum stress increased with the loading rate. The dynamic strength was isotropic at low and high strain rates，but Y-samples had the highest dynamic strength under middle loading rate. The XZ plane was considered to be parallel to the rift plane，thus it was difficult to split the cracks with the critical loading level.

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INVESTIGATION ON FATIGUE CHARACTERISTICS OF WHITE SANDSTONE UNDER CYCLIC LOADING

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2009, 28 (S1): -2749 doi:
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Using rock mechanics test equipment RMT–150B，utilizing two different test methods—one is changing the maximum of cyclic load with the minimum of cyclic load fixed and the other is changing the minimum of cyclic load with the maximum of cyclic load fixed. The fatigue characteristics，the axial strain accumulation rule and the irreversible deformation development law and the relations betweens the axial strain rate and the cyclic numbers of times of white sandstone under the different cyclic loading conditions are studied. The results show that the macroscopic process of white sandstone fatigue failure under cyclic loading is the development of irreversible axial deformation，which finally leads to destruction of rock sample and exhibits three development phases that dont depend on cyclic loading conditions. The fatigue failure curve of white sandstone is controlled by its complete stress-strain curve under static loading. The amplitude and the maximum of cyclic load are the most important factors influencing the process of fatigue failure and fatigue lifespan of white sandstone.

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ANALYSIS OF DEFORMATION OF SANDSTONE
WITH MULTIPLE ACID TREATMENTS UNDER TRIAXIAL CYCLIC COMPRESSION

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2009, 28 (S1): -2755 doi:
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Based on the results of triaxial cyclic on/off loading experiment using the same sample treated by multiple acid，the influence of acid treatment on deformation feature of rock has been analyzed specifically. The results show acid treatment and the quantity of acid flooding have significant effect on deformation of rock. The effect of the acid flooding for the first time is obvious，and the elastic modulus and Poisson’s ratio decrease dramatically in the process loading/unloading. However，the effect is tapering off when the quantity of acid flooding is large enough because of decrease of the lyotrope and dissoluble mineral. Elastic modulus in the process of loading/unloading is decreasing with the increasing of multiple acid treatments，so is the Poisson’s ratio. The changes of elastic modulus and Poisson’s ratio in the early stage are greater，and tend to smooth in the later stage. And the regularity of Poisson’s ratio in the process of loading/unloading is indistinct. When the clyclic load reaches to the maximum value，the axial deformation is increasing gradually with the increasing of quantity of acid flooding. Therefore，acid treatment is one of the important factors that affect the mechanical deformation behavior of rock. In the gas and oil industry，the alternation of loading capacity of rock treated by acid and the negative impacts in the later engineering operation should be noticed.

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ROBUST ARITHMETIC FOR ACOUSTIC EMISSION LOCATION

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2009, 28 (S1): -2760 doi:
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The acoustic emission(AE) 3D location is widely used in rock mechanics experiments，and one of its main disadvantages of the current technique is the low accuracy of general algorithms. It is realized that the random error is the dominating factor which influences the accuracy of AE location the most based on an analysis of many algorithms and a check with an artificial AE shock excitation. Therefore，least absolute deviation，which is more robust than least squares especially for Gaussian noise，is selected to reduce the random error. Experimental results show that compared with least squares，least absolute deviation can improve location accuracy effectively considering the existence of several outliers.

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RESEARCH PROGRESS OF GEOMECHANICAL MODEL TEST WITH NEW TECHNOLOGY AND ITS ENGINEERING APPLICATION

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2009, 28 (S1): -2765 doi:
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The research progress of geomechanical model test are introduced，including new model material，combination test apparatus and new measurement technologies of strain and displacement and so on. New model material can simulate engineering rock mass better and has characters of low cost，easily drying and recycling. 他The developed combination test apparatus can assemble freely and has high stiffness and good integral stability. Hydraulic pressure loading system can implement automatic servo-controlled and ladder-shaped loading. Strain can be measured by advanced high-speed static strain collection analysis system and fiber measurement technology. Model interior displacement can be measured by the developed fiber Bragg grating mini-type multi-point extensometer. The surface displacement of tunnel can be measured by calipers，photograph measure and CCD laser displacement sensor. These measuring methods mentioned above have characters of automatization，high precision and less disturbance，which can get more accurate test results. Finally，an example is provided to illuminate the application of geomechanical model test in forked tunnel research.

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EXPERIMENTAL STUDY ON BRITTLE ROCK FAILURE

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2009, 28 (S1): -2772 doi:
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[PDF 323 KB] (1993)

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Uniaxial compressive tests on standard granite specimen and granite plate with circular hole at center are carried out under different loading rates；and the whole process of rock failure is studied and the characteristics of acoustic emission in the process of rock failure are analyzed. The crack initiation and propagation are recorded in the whole course. The following conclusions can be drawn from tests. (1) Rock failure is a reflection of the crack initiation and propagation. The acoustic emission(AE) phenomenon can show the laws of crack initiation and propagation. (2) Under different loading rates，the specimen has different ultimate bearing capacities and failure modes. (3) Based on the test results，a constitutive relation of elastobrittle material with damage is established，and with the implementation of the secondary development of ABAQUS，the model is studied with numerical simulation under the same condition of the test，then the experimental results are compared with those of numerical simulation. The results of simulation calculations truly reflect the full process of rock deformation and failure. The research results play a great role in the strength criteria of rock fracture and rockburst mechanism.

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DISCONTINUOUS DEFORMATION ANALYSIS METHOD BASED ON NEWMARK INTEGRATION ALGORITHM

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2009, 28 (S1): -2778 doi:
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[PDF 286 KB] (1515)

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Time integration theories applicable to the discontinuous deformation analysis(DDA) method are studied. The general formulae of the global increment displacement solution algorithm for the DDA by using Newmark method are presented. By changing the collocation parameters in Newmark method，a variety of well- known time integration algorithms are produced，including the constant，average and linear acceleration schemes. To ensure the stability of the integration algorithms，a self-adaptive damping which is in direct proportion to the imbalance force is introduced to consider energy losses for block system. An example of tunnel excavation has been analyzed，and the results are compared with those obtained by UDEC to evaluate the performance of the Newmark integration algorithms. The numerical results show the validity and the reliability of the improved DDA method.

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EXPERIMENTAL STUDY ON EFFECT OF TEMPERATURE ON SANDSTONE DAMAGE

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2009, 28 (S1): -2784 doi:
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Sandstone specimen is adopted to conduct test，and all of the homogeneity of specimen and the law of ultrasonic wave and porosity are studied before and after high temperature. Through the experimental study on the law of ultrasonic wave and porosity，the law of effect of temperature on sandstone damage is obtained. The result shows that the ultrasonic velocity increases except when the temperature is 200 ℃；the ultrasonic velocity will decrease when the temperature increases；the porosity will increase as the temperature increases. The two facts show that sandstone specimen is damaged after high temperature. The relation between ultrasonic velocity and damage factor is obtained，and the damage factor will increase as the temperature increases.

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FRACTURE TOUGHNESS MEASUREMENT OF ROCK WITH FRACTAL CRACKS USING HYDRAULIC FRACTURING

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2009, 28 (S1): -2789 doi:
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[PDF 212 KB] (1015)

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The fractal methods are used to describe the tortuous shape of rock fracture cracks，and the theoretical models for fracture toughness of rock with fractal cracks are built. Based on these and different assumptions，the rock fracture toughness has been determined with rock fracture toughness testing system，which is self-developed and has the internal pressure. The results show that the fracture toughness of rock with fractal cracks is greater than that obtained by linear model，which also confirms that the theoretical values are often lower than the actual pressures of hydraulic fracturing operations at present. It is further proved that the calculation results with this model are closer to the actual ones.

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EXPERIMENTAL ANALYSIS OF INFLUENCE OF PERMEABILITY SCALE EFFECT ON RELAXATION UNDER LOW FREQUENCY

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2009, 28 (S1): -2794 doi:
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It is known that viscous and inertial coupling between the frame of a porous rock and its pore fluid dissipates seismic energy by conversion to heat and hence will cause attenuation. Cole-Cole distribution modified Debye model is always used to explain the internal friction of rock. However，this model is suitable only for homogeneous medium，not quite suitable for complex fluid saturated porous rock medium. Obviously，internal friction experimental data under low frequency condition are not coincident with Cole-Cole distribution modified Debye model. Their Re-Im modulus curves do not have the common “arc-shaped” features represented by Debye model. It is suggested that the behaviours of Re-Im modulus curves can be explained by permeability scale effect in wave-induced fluid relaxation of porous rock medium，which is necessary to be extension to Cole-Cole distribution modified Debye model. Internal friction experimental data show that all the Im-Re curves are alike，with same asymmetric arc-shaped form in both high and low temperature. Especially in low temperature，the curves separate and ascend，and ascend more acutely as the frequency increases. Thats a certain evidence of permeability scale effect in fluid relaxation of heterogeneous rocks with micro-cracks. It can be used to improve methods of geological interpretation of acoustical and seismic data and helps to improve the model containing relaxation mechanism of saturated rocks，and to explain the relevant experimental data reasonably. Based on research of predictive model of the relaxation behaviours of fluid saturated rocks，multi-scale structural information about the heterogeneous rocks may be picked up from the experimental data.

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IN-SITU STRESS MEASUREMENT OF RESERVOIR
USING KAISER EFFECT OF ROCK

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2009, 28 (S1): -2802 doi:
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The acoustic emission(AE) technique is investigated to measure rock in-situ stress using the Kaiser effect of rock under uniaxial compression，which characterizes AE increase in an increasing stress exceeds the previous stress. The rock cores are obtained from the vertically drilled exploratory boreholes in Jingan oil field. It is shown that the commonly used Kaiser effect method for estimating in-situ stress is in accordance with the results obtained by instantaneous shut-in method of hydraulic fracturing. And the orientation of the maximum horizontal stress in reservoir by Kaiser effect combining paleomagnetic orientation of cores is also accordance with the results obtained by diplog.

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STUDY ON PATTERN RECOGNITION MODEL OF GROUNDWATER SEEPAGE FIELD IN RESERVOIR AND DAM SITES

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2009, 28 (S1): -2808 doi:
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[PDF 336 KB] (757)

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The advantages with the use of the pattern recognition method to study the characteristic of the reservoir and dam groundwater seepage field are described briefly. According to the theory of fuzzy selection，the mixing ratio model is built. It presents the criteria to classify the water samples quantitatively through application based on the difference and relation among various samples，and offers the precondition in order to describe target pattern. According to the basic concept of pattern recognition and combining with the theory of multifunction and BP network，the multi-factor increment model is established. The target value of each pattern is unique. The model can filter and harmonize valuable information，and deduce the target model value by analyzing the increment between known and unknown variables. An instance of Longyangxia dam groundwater seepage field is provided. It shows that there are so many merits about the pattern recognition method within the research domain of groundwater seepage field characteristic and supply relationship，such as the interfere from subjective or impersonality is avoidable，it is easy to program，the process and results are clear.

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STUDY ON FRACTURE MECHANISM OF OVERLYING
SUPER-THICK ROCK STRATUM IN UNDERGROUND MINING

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2009, 28 (S1): -2815 doi:
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The key stratum controls the deformation and failure modes of the mining rock mass. Based on mining condition which is covered by super-thick magmatic stratum，failure conditions and failure modes of magmatic stratum are studied by means of analytical solution—theory of thick plate rested on elastic foundation when mining is carried out in different stages. It indicates that overlying strata gradually break down and separation appears under the magmatic rock when the mining length increases. Tensile fractures could occur in the midpoint of the boundary in top side when mining at certain distance，then shear fracture could occur in the midpoint of the long sides in the central plan when the length of work face increases. After that，tensile fracture could occur in the midpoint of the up side and propagate to all round sides gradually if the length of work face keeps on increasing. At last，midpoint of the short boundary in the central plan fractures because of the shear stress along the thickness direction. The working face mining distance can decrease when fracture occurs and the mining width increases.

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NUMERICAL SIMULATION OF ROCK DEFORMATION AND SEEPAGE FIELD WITH A FULLY-WATER KARSTIC COLLAPSE COLUMN UNDER MINING INFLUENCE

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2009, 28 (S1): -2824 doi:
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The deformation of surrounding rock and the seepage field of pore water with a fully-water karstic collapse column in the process of coal mining are numerically simulated by finite element method，in which elastoplastic constitutive model for the coal layer and the surrounding rock and Darcys seepage model for pore water are adopted. The body force is introduced to describe the coupling influence of pore water pressure on the deformation of surrounding rock. The varying characteristics of stress，plastic deformation and seepage velocity with the mining process are probed. The damage areas in the surrounding rock and the coal layer with the decrease of the distance between the mining face and the karstic collapse columns are computed，and the distance from the mining face to the karstic collapse columns needed as the reserved coal column for prevention of water inrush is also quantitatively given. Besides，the results for two cases，one with the existence of the body force and another without the existence of the body force ，are compared to show the effect of solid-liquid coupling. The result is helpful for coal mining design under complicated geological structure. It is also useful for further analysis of fluid-solid coupling，and study of the mechanism of water inrush from coal floor，as well as proper design of coal pillar to prevent water inrush in coal layer.

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EXPERIMENT RESEARCH ON LOW PERMEABILITY RESERVOIR
IMPROVED BY EXPLOSION TECHNOLOGY

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2009, 28 (S1): -2830 doi:
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[PDF 324 KB] (805)

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In order to exploit the low permeability reservoir effectively，the stimulation technology of exploding in fracture is introduced. By the experiment of exploding on the surface of the cement sample in deep water，the phenomenon of the formation rock damage and fracture by exploding wave is simulated. Through optimizing the experiment scheme，there are 3 damage zones are observed，namely，the compressive shear damage zone，the tension damage zone and the damage zone on the boundary；and the initiation and propagation of the micro-fracture have a close relationship with the initial damage of the cement sample. The fracture density in the shear damage zone and tension damage zone has a relationship with the equivalent radius of the explosive load；and the scales of the compressive shear damage zone and the tensile damage zone are 2–5 times and 20–30 times of the equivalent radius of the explosive load respectively. By dimension analysis，it is found that the scales of the shear damage zone and the tension damage zone have a linear relationship with the equivalent radius of the explosive. By simple experiment，it is found that the compressive shear area has finite permeability，which has an important meaning to exploding in fracture. At last，the exploding wave propagation progress and the damage and fracture mechanism are both explained qualitatively.

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IDENTIFICATION OF ARRIVING TIME OF VIBRATION INDUCED BY GEOSTRESS DYNAMIC UNLOADING DURING BLASTING-EXCAVATION EMPLOYING METHOD OF TIME-ENERGY ANALYSIS BASED ON WAVELET TRANSFORM

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2009, 28 (S1): -2836 doi:
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THREE-DIMENSIONAL NUMERICAL SIMULATION FOR PROTECTION SCOPE OF STEEP INCLINED UPPER-PROTECTIVE LAYER OF PITCHING OBLIQUE MINING

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2009, 28 (S1): -2845 doi:
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Aimed at the problem of locating the protection scope of steep inclined upper-protective layer of pitching oblique mining(POM)，based on finite element method and the geological properties and the physico-mechanical parameters of roof and floor rock strata of protective layer，the changing processes of stress field and deformation field of protective layer after exploiting steep inclined upper-protective layer of POM are simulated by 3D-σ software. Then，the protecting effect of protective layer is gotten，while the changing laws of the maximum principal stress and deformation of protective layer along with the exploitation of upper-protective layer are analyzed. According to the protection rule of the deformation and stress-relief in exploiting protective layer，the inclination and strike protection scopes of protective layer are located. The results show that the upper and downside stress-relief angles along inclination of steep inclined upper-protective layer of POM are 84.9° and 68° ，respectively；The distribution of strike stress-relief angles along inclination of working face is uneven everywhere，and their values are 38.3°–51.0°. And the protection scopes of steep inclined upper-protective layer of POM located by the method of practical test and numerical simulation are basically consistent. The conclusion can be drawn that it is feasible to study the protection scope of steep inclined upper-protective layer of POM by using numerical simulation and its results are acceptable.

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3D NUMERICAL SIMULATION OF EFFECT OF UNDERGROUND URBAN STREET-PASSAGE TUNNEL CONSTRUCTION ON ADJACENT PIPELINE

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2009, 28 (S1): -2853 doi:
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Three-dimensional finite element analysis model is established to simulate the effects of tunnel excavation on adjacent underground pipeline. The influences of pavement，pipeline material，buried depth，spacing distance between pipeline and tunnel，and elastic modulus ratio of soil and pipeline on the displacement of underground pipeline is discussed. Then the calculation values are compared with the test values. It shows that the results of finite element numerical simulation are well in accordance with but slightly larger than measured data. Displacement of shallow-buried pipeline decreases and settlement trough width becomes narrow due to the existence of pavement. Horizontal displacement of underground pipeline induced by tunnel excavation is far less than vertical displacement. The maximum horizontal displacement and vertical displacement of pipeline perpendicularly crossing with tunnel change linearly with buried depth of pipelines，and decrease with the increase of elastic modulus ratio of soil and pipeline. Defining L as ratio of distance between axial lines of pipeline and tunnel，and h as buried depth of pipelines，The maximum horizontal displacement and vertical displacement of pipeline parallel with tunnel decrease with the increase of L/h. The maximum horizontal displacement changes linearly with L/h，and the maximum vertical displacement increases quickly when L/h＜10. The maximum stress of pipeline decreases with the increase of L/h，and increases quickly when L/h＜5. The maximum stress of pipeline changes slowly with small value when L/h≥5.

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MECHANISM ANALYSIS OF INTEGRAL SUBSIDENCE OF UPPER STRATUM IN URBAN TUNNELS

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2009, 28 (S1): -2860 doi:
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By in-situ monitoring in Beijing metro，Shenzhen metro，Xiamen subsea tunnel，and Xiamen airport road tunnel etc.，its found that there are big differences between urban shallow-buried tunnel and mountain one both in stratum deformation and rock wall pressure. Upper strata in city tunnels subside as a whole，and the subsidence develops more suddenly and devastatingly. Faced with these complex situations，a new model for stratum slipping and cracking is established，and the deduced results show that stratum slipping angle is 15° higher than traditional one，thus relative slipping surface is steeper，closer to vertical direction. And the slipping angle is a function of rock properties，stress fields，tunnel depth versus span，and rise-span ratio，which to some extend testifies that the deformation and failure of rock wall embody scale effects，thats to say，the geometrical properties of rock wall jointing with mechanical parameters will call for stratum integral subsidence，collapse，and roof fall behavior. Besides，soil below tunnel structure，being disturbed，damaged，and softened，may easily drive under-stratum into subsiding and losing bearing capacity，further bringing integral subsidence of supporting structure，and finally sharpening integral subsidence of upper-stratum. Correspondingly ideal elastoplastic model and modified Cam-Clay numerical model can partially lead to the similar conclusion. Synthetically research shows that its vital necessary to acknowledge urban shallow-buried tunnel from rock wall mechanical behavior and its constitutive law.

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RESEARCH ON TEMPORAL-SPATIAL DISTRIBUTION LAWS OF ELECTROMAGNETIC EMISSION DURING TUNNEL
EXCAVATION OF COAL ROCK

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2009, 28 (S1): -2868 doi:
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[PDF 391 KB] (942)

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First the distribution laws of stress fields in the course of mine tunnel excavation are simulated by means of FLAC3D software. Then，according to the coupling equation between electromagnetic emission(EME) and stress fields during the deformation and fracture of coal or rock，the temporal-spatial distribution laws of EME during mine tunnel excavation are also researched. The results show that the changing rules of simulated stress are in accordance with theoretical ones and practical strata stresses，which shows that the FLAC3D can appropriately simulate the changing rules of stress field in the course of mine tunnel excavation. The spatial distribution laws of EME are that the EME signals have smaller values when being monitored in the roof of tunnel than those in the middle of tunnel along the height of tunnel，and the EME signals have smaller values when being monitored in the left side or right side of tunnel than those in the middle of tunnel along the horizontal direction of tunnel. The EME signal in head-on area along the way of tunnel excavation increases constantly to the summit value，and then falls down. The temporal distribution laws of EME are that EME in the same monitoring place increases firstly，and then increases slightly with time. The change of EME strength reflects the change of inner stress after excavation. The practically measured results of EME have the same changing tendency with the simulated results，which also testifies the feasibility of the coupling method between EME and stress to study the temporal- spatial distribution laws.

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COUPLED THERMO-MECHANICAL ANALYSIS OF GRANITE FOR HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY

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2009, 28 (S1): -2875 doi:
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[PDF 739 KB] (1038)

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Based on the conceptual model of high-level radioactive wastes(HLW) repository，the temperature field，stress field and deformation field of HLW repository surrounding rock are calculated under the condition of thermo-mechanical(TM) coupling by using finite difference program FLAC3D. From this study，the thermo- mechanical characteristic of granite is obtained primarily under the given canister heat source and the decay law function is presented. These results show that the reasonable spacing between disposal hole is 8–12 m，and the peak temperature of the canister surface is 130 ℃，the centerline temperature among pits is about 40 ℃，which lasts for about hundreds of years under given heating output at depth of －500 m.

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ANALYSES OF BLOCK DEFORMATION CHARACTERISTICS OF LARGE UNDERGROUND CAVERN AND ITS STABILITY UNDER HIGH IN-SITU STRESS

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2009, 28 (S1): -2884 doi:
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The powerhouse of Laxiwa hydropower station is a lager cavern，where the in-situ stress is 10 to 30 MPa，belonging to high in-situ stress region. Faults f10，f12 and f24 are located in the region A of cavern upstream sidewall. By the analysis of lower hemisphere joint plane projection，it is known that faults f10，f12 and f24 can form key block with volume 2 103 m3. During the course of the cavern excavation，because of action of stress release and adjustment，in period of acceleration deformation，the maximum rate of block deformation reaches 1.22 mm/d，therefore，the stability degree of block is significant to define bolt parameters of region A. Multi-parameter analyses of block unstable mode and stability are conducted by block theory. It is determined that block deformation belongs to the unloading one induced by excavation，but not sliding displacement. Based on block deformation monitoring and stability analysis，only structural reinforcement without special functional reinforcement is carried out，which reduces supporting engineering quantity and improves the construction speed. The results show that，under high in-situ stress，the block large underground cavern is stable，if the block deformation has no influence on the safety of other structures，the unloading deformation is allowable for block without special reinforcement measures.

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RESEARCH ON GROUNDWATER TRANSPORT，INFLUENCE AND CONTROL IN TUNNELGROUP OF JINPING II HYDROPOWER STATION DURING CONSTRUCTION

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2009, 28 (S1): -2891 doi:
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[PDF 458 KB] (940)

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It is inevitable that the building of long deep-buried tunnels in water-enriched area will destroy the original balance of groundwater，which will have negative effects on construction and hydrogeological environment nearby. Water transport in mountain and its influence as well as water inflow into tunnels during excavation are complex three-dimensional(3D) problems influenced by a number of factors. Taking Jinping II hydropower station for example，the transport of groundwater in mountain rock during construction period has been studied. A comparison between the calculated results and the observed data under present circumstances indicates that the method and results are satisfactory，and then the distribution of groundwater after excavation is studied as well as its influence on the two springs(Mofanggou and Laozhangzi springs) nearby and domestic water of local people in construction area. Furthermore，control measures and criteria of water inflow in tunnels are proposed for design and construction.

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STABILITY ANALYSIS OF MIDDLE ROCK PILLAR IN PARALLEL TUNNELS IN HORIZONTALLY INTERBEDDING ROCK MASS

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2009, 28 (S1): -2898 doi:
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[PDF 565 KB] (948)

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Based on the features of the construction of two parallel tunnels excavated in horizontally interbedding rock mass，each rock stratum is regarded as the isotropic continuous medium，and the influence of rock stratum interface is considered，the numerical model is performed on the basis of the assumption. Adopting the FLAC，the stability of middle rock pillar is discussed mainly from the plastic zones and stress distribution of middle rock pillar. In addition，the influences of the different net distances between two tunnels and the various surrounding rock conditions on the stability of middle rock pillar are studied. Moreover，it is proposed that the improved method for calculating the safety factor of middle rock pillar is reasonable. The results show that the stability of the middle rock pillar will increase with the increasing net distances between two tunnels and in turns under soft rock，soft-hard interbedding rock and hard rock. It is available to judge the stability of the middle rock pillar in parallel tunnels under interbedding rocks on the basis of general analyses of the plastic zones，stress distribution and the safety factor of middle rock pillar. Furthermore，it is available to adopt the net distance of more than 1.0 time tunnel span under interbedding rocks，the middle rock pillar is stable and the especial reinforcement measures can not be adopted. The results are expected to be useful for the design of two parallel tunnels.

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RESEARCH ON EFFECT OF TIDE ON STABILITIES OF CHANNEL TUNNEL LINING

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2009, 28 (S1): -2905 doi:
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Xiamen subsea tunnel is the longest one which is under construction in China at present. The tunnel and its connection projects are located in Xiamen，Fujian Province. Tidal phenomenon is multiple in this region，and the hydrological condition is complex. The maximum tidal range is 6.92 m in the past years，and the annual average tidal range is 4.01 m. The effects of the tide should be considered when numerical simulations are conducted. Using the monitoring data from the Research Centre of Ocean Engineering，considering the fatigue damage process of lining during tide changes，the influence of tidal load on the stabilities of lining and surrounding rock under hydro-mechanical coupling are analyzed by finite element method. The conclusion will benefit for future subsea tunnel design and practice.

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FAILURE MODES OF BEDDING ROCK CUTTING SLOPE AND DESIGN COUNTERMEASURES

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2009, 28 (S1): -2915 doi:
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Based on the geological investigation on many bedding rock slopes，a slope classification system and eight types of failure modes with respect to bedding rock slope are presented. Furthermore，the analytical methods for stability of slip-fracture and slip-bending failure mode slopes are studied. It is pointed out that the stability analysis of the slip-fracture failure mode slope can be carried out by calculating the ultimate length of the unstable rock formation；slope reinforcement in advance or reinforcement and excavation simultaneously should be adopted to avoid slope failure for this kind of bedding rock slope. For the bedding slopes whose failure mode would be slip-bending due to the excavation of the rock mass along the bedding surface，the slope stability analysis should be introduced firstly by using the compressive elastic slab stability theory，and the step excavation height and reinforcement measures then could be determined. Water is the key factor inducing the failure of bedding rock slope，so the issue to ensure waterproofing and drainage must be considered in the slope design.

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MODEL TEST STUDY ON MECHANISM OF BOLT IN SOFT ROCK TUNNEL

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2009, 28 (S1): -2922 doi:
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With the development of expressway tunnel，its stability is becoming the key problem for design and construction. According to surrounding rock characters of the Gonghe tunnel along Chongqing—Changsha road，model tests of unreinforced tunnel and bolt-reinforced tunnel are conducted on triaxial testing machine. Based on the model test，the complete failure course of surrounding rock is found. The strain gauge is used to record the strain of different parts of the surrounding rock，and the variability of the stress of surrounding rock under different conditions is analyzed. The following conclusions can be drawn. (1) The radial and the tangential stresses increase with the increase of load. (2) The radial stress increases with the increase of the distance from tunnel wall. (3) There is a stress concentration of the tangential stress on the tunnel wall，and the tangential stress decreases with the increase of the distance from the tunnel wall. (4) The radial and the tangential stresses of surrounding rock after reinforcement are higher than those before reinforcement. The bolt improves the stability of the surrounding rock. The reinforcement effect of the long bolt is better than that of the short bolt.

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EFFECT ANALYSIS OF INITIAL VERTICAL GEOSTRESS IN SURROUNDING ROCK ON STRESS DISTRIBUTION MODE OF FULLY GROUTED ROCK BOLT IN CIRCULAR TUNNEL

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2009, 28 (S1): -2928 doi:
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By analyzing the effects of initial vertical geostress on plastic zone radius of circular underground tunnel，displacement changes in plastic and elastic zones of surrounding rock and bolt stress distribution mode，it is revealed that the initial vertical geostress is very important for reinforcement effect. The study results show that the stresses in elastic zone are related with the vertical geostress，but the stresses in plastic zone are opposite. With the vertical geostress increasing，the radius of plastic zone increases；and there is a nonlinear relation between the vertical stress and the radius of plastic zone. The radial displacements in plastic zone and the maximum displacement of tunnel wall increase with the increase of the vertical geostress. Based on the interaction between rock mass and rock bolt，the analytical constitutive equations of stress distribution of fully grouted rock bolt in surrounding rock of circular tunnel are built. On the basis of the model，the stress distribution mode of bolt under different vertical geostresses is analyzed. It is shown that the friction resistance and the axial load increase with the increasing vertical geostress，and stress concentration appears at bolt end more obviously. When the friction resistance at bolt end is more than the allowable shear strength of surrounding rock，the cracking failure happens in bolt and surrounding rock，which should be considered in design and construction. Finally，the method for improving the reinforcement effect when the anchor head cracks is put forward. It is suggested that setting plate can improve the reinforcement effect of fully grouted rock bolt.

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MANUFACTURE AND EXPERIMENTAL STUDY OF A NEW TYPE UMBRELLA-SHAPED ANTI-FLOAT ANCHOR

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2009, 28 (S1): -2935 doi:
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A new type umbrella-shaped anti-float device，being composed of stretching anchor cables and an anchor head that can stretch in soil，is designed to perfect the traditional anchors on the basis of fully integrating with the advantages of under-reamed piles and anchors. There are two groups of pullout tests for umbrella-shaped anchor with and without grouting at anchor head，and a group of vertical pile pullout test is done for comparison. The results indicate that the anti-float performance of the new type anchors is better than traditional vertical piles. Moreover，the pullout behaviour of the umbrella-shaped anchor with grouting in anchor head is better. According to the test，the force mechanism of the umbrella-shaped anchor is further analyzed. It is pointed out that the uplift bearing capacity depends on the weight of soil pole wrapped by the anchor head and the shear friction along the interface of soil pole. Therefore the ultimate bearing capacity estimation formula of the umbrella-shaped anchor can be presented，which establishes the foundation for the engineering application of umbrella-shaped anchors.

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EXPERIMENTAL RESEARCH ON MECHANICAL PROPERTIES OF PIPE MATERIAL FOR BAMBOO-STEEL COMPOSITE ANCHOR BOLT

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2009, 28 (S1): -2941 doi:
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Compressive，tensile and bending strength tests were conducted on bamboo specimens in laboratory to understand the working mechanism of bamboo-steel cable composite(BSCC) anchor，a newly invented anchor for reinforcing earthen archaeological sites. Test results show that the longitudinal compressive strength of the 3 year-old bamboo is up to 119 MPa，which is higher than that of 5 year-old one. With respect to the height positions of the same bamboo，the longitudinal strength is almost the same for the specimens from the middle and bottom parts，but less than that from the top part. The relationship between compressive direction and arrangement of bamboo fiber is highly responsible for the variation of compressive strength of bamboo，namely，the longitudinal，tangential and radial strengths are 98，37 and 65 MPa respectively. The compressive，tensile and bending strengths of bamboo specimens are found to decrease gradually with the increase of moisture content except that the compressive strength becomes stable when the moisture content is greater than a constant. Compressive tests on bamboo pipes in two different diameter-to-height ratios，1∶1 and 1∶2，and tensile tests on bamboo splints，illustrate that the existence of bamboo knots results to a little decrease in bamboo pipe and splint strengths.

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RESEARCH ON INTERACTION MECHANISM BETWEEN LATTICE BEAM AND SLOPE ROCK MASS AND FIELD TEST

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2009, 28 (S1): -2947 doi:
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Based on analytical solution derived from deformation coordination equation of hypothesis elastic foundation beam and Winkler foundation model，the interaction mechanism between lattice beam and slope rock mass is analyzed，depending on Shunxichang landslide treatment engineering in Zhongxian county. Lattice beam with cross section 0.4 m×0.5 m and anchor rope with space 4 m×4 m are designed. Factual variation of inner force of lattice beam is obtained in the process of loading，and then the assignment of anchor forces in the longitudinal beam and transverse beam is discussed mainly. In field test，the interaction mechanism between lattice beam and slope rock mass is considered，and the problems that the parameters of rock mass are difficult to be determined accurately by numerical method and the complex situations that are difficult to be solved by analytical method are overcome. It has reference value for optimal design of lattice beam structure.
slope rock mass；interaction；field test

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INFLUENCE OF STRETCHING TECHNOLOGY ON LOAD NON-UNIFORM COEFFICIENT OF PRESSURE-DISPERSIVE ANCHOR CABLE

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2009, 28 (S1): -2954 doi:
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The pressure-dispersive anchor cable is gradually applied to domestic rock and soil reinforcement engineering recently because of the advantages of stress uniform distribution in anchorage section and reliable anti-corrosion capability，and it can supply bearing capacity which is several times as high as that provided by tension anchor cable. The load difference of loading body cell can bring disadvantage effect to anchor cable reinforcement. The load non-uniform coefficient of pressure-dispersive anchor cable is discussed and analyzed under conditions of different stretching technologies，and the method to eliminate and decrease the non-uniform load coefficient is discussed. Aiming at different engineering conditions，by adjusting the stretching technology of anchor cable，the load non-uniform coefficient can be reduced greatly，which shows that the pressure-dispersive anchor cable can be used to temporary works and permanent engineering.

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DESIGN AND APPLICATION OF ANTI-FLOATING ANCHORED STRUCTURE BY BLAST-EXPANDING BORE IN LARGE-SCALE UNDERGROUND SEWAGE POOL

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2009, 28 (S1): -2960 doi:
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According to the structure and geological feature of sewage pool and integrated analysis of various anti-floating methods，the type of the anti-floating anchor with blast-expanding bore and variable section are put forward. Those ways can solve the anti-floating problem and ensure the sewage pool can be put into production as soon as possible. Because of end effects of the anchorage and the expanding part at the bore end，not only the bond strength of anchor can be improved effectively，but also the depth and diameter of the bore are shortened，and the construction efficiency is significantly enhanced. The method of blast-expanding bore can squeeze soil rapidly around the anchor bore，expand the bore section，raise the bond strength between soil and grouting body，and increase the anchoring force of anchors. Practice has proved that，as a reinforcement method of engineering anti-float，its a cost-effective and efficient anti-floating method to combine anti-floating anchor and blast- expanding bore. This can provide reference to the similar projects in design and construction.

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STUDY ON DYNAMIC COMPACTION REPLACEMENT
FOR REINFORCING FREEWAY ROADBED IN WETLANDS

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2009, 28 (S1): -2966 doi:
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The road from Hailaer to Manzhouli passes through the Hailaer wetlands，where a thin soft soil layer exists on the ground surface. Furthermore，the ground water level is so high that in rainy seasons it rises over the ground surface. The dynamic replacement method(DRM) is chosen to comprehensively consider the feasibility of construction and economic effects. According to the design，some large diameter piles are formed by filling the rammed holes with crushed stones which are acting as the skeleton of the composite foundation. Dynamic compaction replacement is an economical，simple and convenient method for soil improvement，but there is no mature method for design and calculation，so before construction，representative field is often chosen in which field experiments are done in order to confirm applicability and the effects of reinforcement. Firstly，the effect of pile diameter on reinforcement results under a certain replacement ratio is studied using the finite element method. Based on the calculation results of the FE method，the diameter of the pile can be chosen and applied to in-situ construction. Through experimental research of dynamic replacement in the typical field，construction parameters are confirmed，and the rationality of this method used to improve this kind of soil foundation is validated.

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STRESS-STAIN RELATION OF SOFT SOIL BASED ON FRACTIONAL CALCULUS OPERATORS THEORY

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2009, 28 (S1): -2973 doi:
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On the basis of the fractional calculus operator theory，the stress-strain relation of soft soil under the condition of loading with constant strain rate is proposed. The analysis results show that stress–strain of soft soil performs exponent relation，which can be proved by large amounts of triaxial tests(under constant strain rate). It is found that the order of fractional calculus keeps constant to the same kind of soil and characterize soft or hard soil. The test results show that there is a linear relationship between confining pressures and initial tangent modulus. Compared with Duncan-Chang model that hypothesizes stress-strain relation is hyperbolic in response to similar shape of experimental curve，the stress-strain relation from the fractional calculus has rigorous theoretical background. The major innovation of our researches is that the soil is considered as the matter whose behaviors are intermediate between that of the ideal solid and fluid，and it also may be the first known application of fractional calculus in soil stress-strain relation.

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CASE STUDY OF DRIP INJECTION OF CHEMICAL GROUTS IN EARTHEN RUINS REINFORCEMENT

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2009, 28 (S1): -2980 doi:
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Weathering prevention is one of the difficulties in earthen ruins conservation. The self-developed drip injection apparatus of chemical grouts is first applied to engineering practice to perform chemical reinforcement on the surface of Dougaeri earthen ruins No.2. The main contents include drip injection of chemical grouts in laboratory model ground，the strength characteristics of chemical grouted soil by triaxial tests，microstructures investigated by SEM observation，drip injection in field model earthen kiln，and reinforcement of Dougaeri earthen kiln No.2 by drip injection of chemical grouts. The test results show that：(1) the balloon cover injection tip specially developed for the drip injection tube can prohibits chemical grout flowing upward to the ground surface，in particular it can implement down-to-up chemical grouting on the top of underground earthen ruins due to its soft and tight attachment with the drill hole sides；(2) chemical grouts(ethyl silicate) can increase cohesion effectively，but it has little influence on the internal friction angle；(3) the thickness of chemical grouted soil by the drip injection apparatus is much larger than that of spraying chemical grouts on the surface of earthen sites；and (4) the field feasibility and adaptability of the drip injection apparatus has been verified by its successful application on strengthening Dougaeri earthen kiln No.2，which will benefit to preservation of other similar earthen ruins.

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BEARING BEHAVIOR OF KINGTOWER FOUNDATION PILE OF JIAJIANG BRIDGE IN NANJING

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2009, 28 (S1): -2986 doi:
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Based on the data of static load test and results of ANSYS analysis，the bearing behavior of large-diameter and extra-long rock-socketed piles are studied. The settlement，the optimized rock socket depth，the distribution of side friction resistance and end resistance are mainly discussed. The results indicate (1) large-diameter and extra-long rock-socketed piles are generally end load friction piles，however，their end resistances cannot be neglected yet；(2) in the socketed section，the distribution of side friction resistance has obvious nonlinear characteristics，which are small at middle and big at both ends；(3) it is not effective to control pile head settlement only by increasing socket depth，and the rock socket depth can not be limited to the norms，which is less than five times of pile diameter. Therefore，some proposals are given to the design of piles.

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RESEARCH ON MODEL TEST OF SOIL NAILED SLOPE ON UNSATURATED COMPACTED SOILS UNDER CYCLIC LOAD

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2009, 28 (S1): -2994 doi:
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A laboratory model for studying dynamic behaviour of soil nailed slope under cyclic load is designed. The sinusoidal cyclic load is produced by a multi-channel load system with four kinds of load magnitude，which are 10–30，30–50，40–60，40–80 kN，and the frequency is 2 Hz. Considering boundary condition influence and accumulative effect of cyclic numbers，axial force of soil nails，displacement and acceleration of the panel，and settlement of top surface，are studied in detail. When the load is 10–30 kN，test results with fixed bilateral boundaries are compared with free ones. Axial force of soil nails and displacement of the panel in the former case are less than that in the latter one under the same cyclic numbers. Then comparative experiments with 4 kinds of load magnitudes with free lateral boundaries are studied. With a certain load magnitude， with increase of cyclic numbers，acceleration and displacement of the panel increases slowly，whereas settlement of top surface increases distinguishedly. With the same cyclic numbers，with increase of average load magnitude，acceleration of panel doesnt vary obviously，nevertheless axial force of soil nails，displacement of the panel and settlement of top surface increase significantly，and displacement along slope height is parabolic curve like.

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MODEL TESTS OF CHARACTERISTICS PILE-SOIL-CAP INTERACTION BASED ON DIGITAL IMAGE CORRELATION METHOD

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2009, 28 (S1): -3001 doi:
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Based on digital image correlation method，a deformation measurement procedure(DIC) has been worked out to study the pile-soil-cap nonlinear interaction mechanism. A series of images are captured by digital camera in the model test，and the images are analyzed by the DIC procedure. Bearing capacity and displacement field of soil beneath cap are obtained during the analysis. The failure pattern of pile foundation is deduced. The test results show that it is viable to analyze the displacement around pile by DIC procedure，and a full displacement field is obtained from image analysis. The deformation behavior of the group piles with 6b spacing is similar to that of single raft foundation. The soil lateral deformation of group piles with 6b spacing is larger than that of 3b spacing，and the pile barrier effect on soil lateral deformation decreases with the increase of pile spacing. The compression region is mainly centralized beneath the pile tip to the 3b spacing foundation，which presents a destruction pattern of block deep foundation. As the increase of pile spacing，the compression region transfers from pile tip to the soil among piles. Group piles with 6b spacing are destroyed by the lateral extrusion of the soil around piles. It is shown that validate the theory of composite pile foundation is validated and 6b spacing is the dividing value between the normally pile foundation and the composite pile foundation.

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AN ANALYTICAL CALCULATION METHOD FOR DISPLACEMENT OF UNDER-REAMED TENSION PILES

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2009, 28 (S1): -3008 doi:
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The belled-out section of under-reamed piles is supposed as spring，and the non-dimension solutions of elastic displacement are deduced according to the equilibrium differential equation of under-reamed piles. The ideal elastic-plastic load-transfer functions for pile shaft are adopted to study the nonlinear deformation of the under-reamed tension piles. The lateral soil strength is regarded as power function，which varies with the depth. On this basis，a series of the closed-form elastic-plastic solutions of displacement and axial load at a certain depth from the ground surface of under-reamed tension pile are deduced. Comparing with the actual responses of the model experiment and in-situ pile test，this proposed method can give reasonable results. The theory solutions not only avoids complex calculation but also predicts the displacement of under-reamed tension piles reasonablely. It can be applied to the actual projects.

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INFLUENCE ANALYSIS OF EXCAVATION OF DEEP PIT ON ADJACENT BURIED PIPELINES

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2009, 28 (S1): -3015 doi:
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In order to study the evaluation method of influence of deep excavation on adjacent buried utilities the influence of excavation on adjacent pipelines with varied diameters is analyzed by FLAC3D. The results indicate that pipeline diameter is important to the interaction between pipeline and soil；When pipeline diameter is less than 400 mm，the pipelines have the same displacement as surrounding soil；when the pipeline diameter is larger than 400 mm，the interaction between pipelines and soil should be taken into account. Furthermore，the maximum value of curvature，angle of rotation，stress and moment of flexure of pipeline all appear at the corner of pit with 20% excavation length. Based on the numeral analysis，a simplified method for calculating deformation and internal force of pipelines with small diameter and the evaluation grade of pipeline safety are put forward.

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LARGE-SCALE SHAKING TABLE TEST FOR VIBRATION-ABSORPTION MEASURES OF PORTAL SECTION OF HUANGCAOPING TUNNEL NO.2

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2009, 28 (S1): -3021 doi:
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The bearing capacity of shallow foundations obtained by the conventional approaches，which assume fully saturated conditions ignoring the influence of the matric suction，may not be reliable and lead to uneconomical designs. On the assumption that the shear strength formula of unsaturated soils is the extension and expansion of the shear strength formula of saturated soils，and based on the linear failure criterion and associated flow rule，the bearing capacity of strip footing on unsaturated soils under the action of ultimate loads is studied by means of the kinematical approach of limit analysis theory. A planar knematically admissible failure mechanism is proposed for the calculation schemes. The objective functions of bearing capacity are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities，and then the objective function is transformed as a upper-bound mathematic optimization model for bearing capacity as low as possible. The objective functions are obtained by use of the sequential quadratic programming. The bearing capacity of unsaturated soil is predicted by using the approach presented above，in which not only the effective internal friction angle，effective cohesion and matric suction，but also the soil-water characteristic curve and the engineering practice are analyzed synthetically. Numerical results show that the existence of matric suction，the distribution mode of matric suction and under water level in unsaturated soils have significant effects on the ultimate bearing capacity. The parametric analysis indicats that preferences possessing nonlinear effect on the bearing capacity. If the yield criterion of unsaturated soils turns into the yield criterion of saturated soils，the presented solution provides better upper-bound result.

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STUDY OF ACTIVE EARTH AND WATER PRESSURE OF RIGID RETAINING WALL CONSIDERING SOIL ARCHING AND SEEPAGE

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2009, 28 (S1): -3029 doi:
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On the basis of the assumption that minor principal stress trace is parabola，the soil arching behind rigid retaining wall is analyzed. The coefficients of active earth and water pressure(AWP) and the horizontal differential element interlayer are obtained. The two-dimensional Laplace equation of the stable seepage field behind rigid retaining wall is also established during continuous rainfall. Based on the analysis of considering，the calculating model of AWP is presented. The formulas of the resultant force，the point of resultant force and the practical coefficient of AWP are proposed. The result of theory analysis shows that the theory value is consisted with the experimental value. When the soil arching and the stable seepage are considered，the distribution of AWP is nonlinear，and the resultant force increases，and the point of resultant force is higher. Therefore，the adverse effect of the soil arching and seepage on the safety of rigid retaining wall should be highly emphasized in the engineering practice. The practical coefficient method of AWP is available for the simplified and practical calculating method of AWP during continuous rainfall.

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BEARING CAPACITY AND DEFORMATION CHARACTERISTIC OF A COMPOSITE FOUNDATION WITH DRIVEN CAST-IN-PLACE Y PILES

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2009, 28 (S1): -3036 doi:
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A new driven cast-in-place Y pile，developed according to the innovative design concept of Y pile and the traditional construction technology of driven cast-in-place pile in China，was introduced in this paper. The newly developed piles were used in a ground improvement project for an expressway bridgehead. Based on the theoretical calculation and static load test results，the longitudinal surface area of a Y pile is about 50% more than that of a circular pile for a given cross-sectional area，from which its side friction and bearing capacity is substantially enhanced. The Y pile is either a friction pile or end bearing friction pile from its working mechanism. Based on the field monitoring results and static load test results，the pile-soil stress ratio，surface settlement，lateral deformation of the driven cast-in-place Y pile composite foundation were discussed. The Y pile composite foundation has better bearing characteristics while the foundation settlement and post-construction settlement of embankment are substantially reduced. From the technical and economical point of view，it has certain advantages over other composite foundation on reliable construction quality，significant reinforcement effect and economical rationality. It can be applied to other projects with similar geological conditions.

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ANALYSIS OF CONSOLIDATION OF EQUAL-STRAIN COMPOSITE GROUND UNDER EMBANKMENT

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2009, 28 (S1): -3042 doi:
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The load on the soil is transferred to piles，and the total stresses of pile and soil changed when the equal-strain composite ground under embankment is consolidated. The change of excess pore water pressure isn’t equal to the change of effective stress of composite ground under includincy embankment. The influential factors of consolidation of equal-strain composite ground with piles，including total stress of soil or pile，compressibility and excess pore water pressure of vertical drain，permeability of pile and relative position of vertical drain and pile，are analyzed. The results of analytical solutions considering pore water pressure，degree of consolidation，stress ratio between pile and soil by which permeability of piles，transfer of load between piles and soil，compression and well resistance of vertical drains，is carried out. It shows that impermeable piles can increase the consolidation of ground but permeable piles maybe delay the consolidation；the consolidation of composite ground is highly influenced by the coefficient of consolidation of pile；the degree of consolidation of composite ground treated by piles with high coefficient of consolidation is larger than that with low coefficient of consolidation.

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EXPERIMENTAL STUDY OF INFLUENCE OF DRYING AND WETTING CYCLES ON BEARING CAPACITY OF IMPROVED SOIL BY CMSC SOIL STABILIZED AGENT

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2009, 28 (S1): -3051 doi:
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On the basis of simulating the seasonal climate which alternates between dryness and wetness in some places，making use of the new hit canister to produce the samples，group of tests were performed to study the influence of drying-wetting cycles on bearing capacity of improved soil by CMSC soil stabilized agent. During the process of drying and wetting cycles，the dehydration mass，water absorption mass and California bearing ratio (CBR) of improved soil by CMSC soil stabilized agent were tested. The variation of dehydration mass，water absorption mass and swelling rate，and the influencing mechanism of numbers of drying-wetting cycles on the CBR value were analyzed. It was shown that during the initial stages of drying and wetting cycles，the curing time and the fitting temperature provided by the dehydration process could accelerate the full reaction between the CMSC soil stabilized agent and soil. Meanwhile the cementation between soil particles was strengthened. So along with the process of drying and wetting cycles，the bearing capacity of improved soil increased. And when the number of drying-wetting cycles was 4，the bearing capacity reached the maximum CBR value. When the number of drying-wetting cycles was greater than 4，the actions are coupled of the variable water content and fissures，and the thin fissures were distended and ran through；then the new fissures came into being. So the unitary and homogeneous property of samples were broken and the bearing capacity of improved soil decreased gradually.

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CALCULATION METHOD OF ULTIMATE BEARING CAPACITY OF VERTICAL PULL-OUT SCREW PILE IN SOFT GROUND

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2009, 28 (S1): -3057 doi:
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Based on the bearing capacity characteristics of vertical pull-out screw pile foundation，the limiting embedded depth of first layer lamina(LED) and the limiting space between of laminas(LSB) are proposed according to Meyerhof bearing capacity theory of deep foundation and limiting equilibrium mechanics. The pull-out failure model of multi-layered screw pile foundation is obtained，and the calculation methods of first LED，the conditional estimation of LSB and the ultimate pull-out bearing capacity of the vertical pull-out screw pile foundation are presented. On the basis of the analysis and the calculated bearing capacity of 14 times vertical pull-out field tests of screw pile foundation，the calculation mistakes of ultimate pull-out bearing capacity of screw pile foundation are less than 10% for the comparing the calculation values to the estimated values of 3 types of screw pile. It shows that the failure model of screw pile foundation is close to the practical situation，and the calculation method can be used to estimate the ultimate bearing capacity of screw pile foundations.

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STUDY ON COMPRESSION DEFORMATION OF WARM
AND ICE-ENRICHED FROZEN SOIL

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2009, 28 (S1): -3063 doi:
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The warm and ice-rich frozen soil under an outside load will generate relatively large compression deformation which greatly influences the stability of roadbed. The compression tests of warm and ice-rich frozen soil show that under the constant load and variable temperatures，the compressibility at －1.5 ℃ or －1.0 ℃ is smaller than that at －0.5 ℃ or －0.3 ℃，and the latter accounts for 70% of the total compressibility. Temperature is the key factor to compressibility coefficient of the warm and ice-rich frozen soil. The compressibility coefficient greatly increases with increasing of temperature. When temperature is at －1.5 ℃ and －0.3 ℃，the compressibility coefficient is 0.04 MPa－1 and 0.29 MPa－1，respectively. The numerical calculation of embankment deformation shows that，the maximum value of the embankment settlement deformation is about 20 cm in the coming 50 a when the height of embankment is bigger than the critical height of embankment. The maximum value of 20 cm is certainly acceptable. However，once the height of embankment is less than the critical height of embankment，the thawing settlement deformation of embankment will happen. So the embankment will be steady as long as the heat stability of embankment can meet the design requirement.

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STUDY ON COMPRESSION DEFORMATION OF WARM
AND ICE-ENRICHED FROZEN SOIL

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2009, 28 (S1): -3063 doi:
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The warm and ice-rich frozen soil under an outside load will generate relatively large compression deformation which greatly influences the stability of roadbed. The compression tests of warm and ice-rich frozen soil show that under the constant load and variable temperatures，the compressibility at －1.5 ℃ or －1.0 ℃ is smaller than that at －0.5 ℃ or －0.3 ℃，and the latter accounts for 70% of the total compressibility. Temperature is the key factor to compressibility coefficient of the warm and ice-rich frozen soil. The compressibility coefficient greatly increases with increasing of temperature. When temperature is at －1.5 ℃ and －0.3 ℃，the compressibility coefficient is 0.04 MPa－1 and 0.29 MPa－1，respectively. The numerical calculation of embankment deformation shows that，the maximum value of the embankment settlement deformation is about 20 cm in the coming 50 a when the height of embankment is bigger than the critical height of embankment. The maximum value of 20 cm is certainly acceptable. However，once the height of embankment is less than the critical height of embankment，the thawing settlement deformation of embankment will happen. So the embankment will be steady as long as the heat stability of embankment can meet the design requirement.

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RESEARCH ON SHEAR STRENGTH OF EXPANSIVE SOILS REINFORCED WITH WASTE TIRE POWDERS

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2009, 28 (S1): -3070 doi:
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In order to increase the use of the recycled resources and reduce potential impact of the wasted tires on the environment，the strength of expansive soil improved by wasted tire rubber powder was studied. The expansive soil is mixed with wasted tire rubber powder in a different proportions of 10，20，and 30%，and a different water proportions，which are about 15%，18% and 21%. Then consolidation fast shear tests were conducted. During the tests，impact of normal stress and the amount of rubber powder on the shear strength of the expensive soil are considered. The relationship between shear displacement and the corresponding shear stress relationship are also taken into account. Tests present the characteristics of the improved expansive soil shear strength. It was shown that the internal friction angle and the shear strength of the expansive soil increases as the amount of the wasted tire rubber powder increases；and the internal friction does not have a remarkable change，while the cohesion changes obviously. It confirms the assumption that wasted tire rubber powder can improve the expansive soil greatly. It provides a new improving method to reduce the engineering disaster caused by the expansive soil.

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STUDY ON CREEP PROPERTIES OF RED-BED SOFT ROCK
UNDER STEP LOAD

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2009, 28 (S1): -3076 doi:
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Creep characteristic is one of the most important mechanical characteristics of rock. It controls the stability of rock engineering. Under step load condition，the creep test of red-bed soft rock which was collected in the seventh tunnel of Yintao water transmission engineering in Gansu is performed by using the CSS-44100 electronic servo testing machine. Based on scientific interpretation and analysis of test data，red-bed soft rock has remarkable creep characteristics and Burgers creep model can be applied to characterize the creep of red-bed soft rock. The effect of water content upon strength and creep characteristic are studied it shows that instantaneous strength decreases with increasing of water content. The higher the water content is，the more creep deformation and the time that need reaching steady state and the bigger the rate of creep are. The test results show that the creep testing curves of red-bed soft rock are coincident well with the theoretic curves and the Burgers creep model can be applied to characterize the creep properties of red-bed soft rock.

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RESEARCH ON ABERRATION CORRECTION AND APPLICATION
IN LANDSLIDE GEOMECHANICAL MODEL TEST

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2009, 28 (S1): -3082 doi:
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The test of geomechanical model is an important tool to study the formation mechanism of landslide. Based on analysis of similarity theories of landslide physical model and characteristics of Three Gorges Reservoir Area，the similarity criterions of 17 parameters from the test of landslide geomechanical model were deduced using self-developed large-scale landslide physical model test flume. The correction method of the aberration，which consists of similarity theory of landslide geomechanical model test，was proposed. On the basis of the correction method of the aberration，the new similar conditions and environments are established. The proposed method has been tested in a practical application to Qianjiangping landslide model in Three Gorges Reservoir Area. It shows the initial mechanism of this landslide is two-section that both of retrogressive and non-retrogressive exit，and the proposed method has improved both landslide geomechanical model test and theory.

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EXPERIMENTAL STUDY OF PERMEABILITY AND STRENGTH WEAKENING OF MUDSTONE CONSIDERING EFFECT OF WATER UNDER TYPICAL STRESS STAGES

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2009, 28 (S1): -3089 doi:
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In consideration of water-rock interaction，strength weakening and permeability of the mudstone under different typical stress stages are studied by MTS815.02S servo-controlled rock mechanical test system. Main conclusions are verified by in-situ test using electrical camera. It shows that water-weakened action of specimen is not notable before the peak strength，and the peak strength decreases by 14.5% after affected by water；the water-weakened action is the highest in residual strength stage，steady peak strength decreases about 50%；water-weakened action in plastic stage and elastic stage are in the second place because of self-sealing action of fissures by water argillization action，and the water-weakened action is minimum in the strain softening stage. With the increasing of deformation，permeability variation of specimen is not notable and maintains lower value in the elastic and yield stage. Permeability coefficient begins to increase in the later strain-softening stage and reaches to the peak value in the residual strength stage，and then tends to steady in the plastic compaction stage.

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EVALUATION INDICATOR SYSTEM FOR EFFECT OF ECO-ENGINEERING FOR ROCK SLOPE PROTECTION AND ITS APPLICATION

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2009, 28 (S1): -3095 doi:
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Substrate-vegetation system is the primary functional component of eco-engineering for rock slope protection(EERSP)，its structure and function determine the stability and effectively of EERSP. Based on the results of research related to EERSP at home and abroad，and on stability of the structure and function of the substrate-vegetation system，an attempt has been made to establish five types of evaluating indicators including the substrate of system，the structure of vegetation，the protective function，the functions of matter cycling and the landscape cultural functions with a view of systematical engineering by investigations and studies. Further those five types of indicators were marked off the operable sub-indexes that formed the indicator system for evaluating the performance of EERSP. The appraisal standards of the indicator system were divided into five grades，such as excellent，well，general，poor and worse，which reflected rationally the characters and nature of the substrate- vegetation system，also exhibited mutual restriction and interdependent relationship between the structure and function. This relationship could transform each other under some special conditions. The indicators were used to evaluate the performance of two slope sections in EERSP of the Chongqing—Guizhou highway by combined analytical hierarchy process(AHP) with fuzzy comprehensive evaluation method. The appraisal results coincided with the in-situ observation，which indicated that the indicator system could objectively reflect the performance and the lasting capacity of function of the substrate-vegetation system.

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RESEARCH ON TIME EFFECT OF ROCK WEAKENING BY WATER-ROCK INTERACTION OF REDBEDS IN SICHUAN BASIN

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2009, 28 (S1): -3102 doi:
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Through experiments on 16 sets of samples of red beds collected from 16 reservoirs，the law that the softening coefficients of long-term water-soaked redbeds decrease is obtained. Rock weakening is the result of long-term softening and weathering co-action in lower water level of the rock in the region between the highest and lower water levels. Analytical results show that the softening coefficient of mudstone can be reduced 10%–20% after 30–50 years soaking compared with that obtained in laboratory，while the softening coefficient of silty mudstone can be reduced about 15% after 30–50 years soaking compared with that obtained in laboratory.

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INFLUENCE OF HEAT DISSIPATION OF MAIN TUNNEL STRUCTURE ON FREEZING EFFECT IN CROSS PASSAGE CONSTRUCTION

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2009, 28 (S1): -3109 doi:
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Heat dissipation of tunnel segments can seriously weaken the freezing effect of the soil near the segments in cross passage construction by artificial freezing method. Based on the field monitored temperature data，a study is conducted to investigate the influence of segments heat dissipation on the development of temperature field. The result shows that the influence of heat dissipation is significant both on the temperature field and the thickness of frozen soil wall，both of which are seriously weakened，and that causes a large gap at the opening of the cross passage compared with the uninfluenced area. The thickness of the frozen soil wall in the influenced area at worst just is half of that in the uninfluenced area，which is very dangerous for construction. With the continuation of freezing，the temperature field in the influenced area gradually reaches an equilibrium state of heat exchange，and the temperature changes little even if the freezing time is prolonged，which only lowers the temperature and improves the thickness of the frozen soil wall of uninfluenced area. On the basis of analysis above，the process of frozen soil wall development is plotted. At last，some suggests are brought forward to guide construction of similar projects.

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EXPERIMENTAL STUDY ON CHARACTERISTICS OF WAVE PROPAGATION IN MEDIA CONTAINING INTERMITTENT CRACKS

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2009, 28 (S1): -3116 doi:
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To study the influence of intermittent cracks(joints) on wave propagation in fractured rock media，the rock-like material samples are adopted to simulate rock media with different lengths，thickness，densities，angles and forms of cracks. Supersonic tests on these samples are conducted to study the changes of velocity and amplitude attenuation of longitudinal wave in cracked media. Additionally，the corresponding numerical simulations are conducted to study the characteristics of wave propagation in cracked media with international large-scale geotechnical analysis software FINAL. The numerical results are compared with laboratory results. The research results show that crack length nearly has not influence on longitudinal wave velocity. Attenuation of stress wave amplitude depends on the projection length of cracks which are perpendicular to wave propagation direction. The larger the projected length of crack is，the more the wave amplitude attenuates. With the increasing rows of cracks，the stress wave amplitude will attenuate. The stress wave amplitude of sample with two rows of cracks is about half of that of sample with one row of cracks，and stress wave amplitude of sample with three rows of cracks is about one third of that of sample with one row of cracks. Furthermore，the largest stress wave amplitude will be delayed with the increasing rows of cracks.

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PRELIMINARY STUDY ON MECHANICAL MECHANISM OF SLOPE EARTHQUAKE-INDUCED DEFORMATION

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2009, 28 (S1): -3124 doi:
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In order to analyze the formation mechanism of slope earthquake-induced deformation，combining with the detailed investigation on the earthquake-induced deformation and failure phenomenon caused by Wenchuan earthquake，the comprehensive analysis method，finite element numerical analysis and vibration table simulation experiments are adopted to analyze the earthquake-induced mechanism of single- and double-side slopes. The results show that the earthquake waves will make the stress field of slopes change significantly. The slope body，especially the grade surface，will generate repeatedly tensile and shear actions，of which values and orientations adjust continuously. These actions are significant reasons of slope failure. It is discovered that the shear actions has three representative forms，i.e. first motion tensile and shear acceleration rending effect，repeatedly tensile and shear rending effect，and double-side common shear rending effect. These rending effects have been found in practice. The results can provide references to forecast failure of earthquake-induced slope and reconstruction of powerful foundation after earthquake and hazard-resistant reduction.

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PRELIMINARY STUDY ON MECHANICAL MECHANISM OF SLOPE EARTHQUAKE-INDUCED DEFORMATION

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2009, 28 (S1): -3124 doi:
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In order to analyze the formation mechanism of slope earthquake-induced deformation，combining with the detailed investigation on the earthquake-induced deformation and failure phenomenon caused by Wenchuan earthquake，the comprehensive analysis method，finite element numerical analysis and vibration table simulation experiments are adopted to analyze the earthquake-induced mechanism of single- and double-side slopes. The results show that the earthquake waves will make the stress field of slopes change significantly. The slope body，especially the grade surface，will generate repeatedly tensile and shear actions，of which values and orientations adjust continuously. These actions are significant reasons of slope failure. It is discovered that the shear actions has three representative forms，i.e. first motion tensile and shear acceleration rending effect，repeatedly tensile and shear rending effect，and double-side common shear rending effect. These rending effects have been found in practice. The results can provide references to forecast failure of earthquake-induced slope and reconstruction of powerful foundation after earthquake and hazard-resistant reduction.

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STRUCTURAL DYNAMIC PROPERTIES ANALYSIS FOR PORTAL PART OF MOUNTAIN TUNNEL IN STRONG EARTHQUAKE AREA

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2009, 28 (S1): -3131 doi:
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Based on the mountain tunnel along Yaan—Lugu highway in strong earthquake area，the dynamic response of mountain tunnel has been analyzed by the means of a large-scale shaking table test. The position of the largest dynamic response of the tunnel and its damage modes are basically the same with that of tunnels damaged in Wenchuan earthquake. The stress state of the tunnel is evidently optimized because of the designed shock absorption layer. There are a lot of longitudinal and oblique cracks on the surface of the tunnel portal，and these cracks extend to the ring cracks and do not propagate. Some shock absorption seams should be designed at the tunnel portal part in order to absorb the earthquake wave energy and protect tunnel structure. These results have a certain reference value for aseismic design and construction of mountain tunnels in strong earthquake area.

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ENERGY ANALYSIS OF DYNAMIC RESPONSE SIGNALS DURING DAMAGE PROCESS OF ROOF SURROUNDING ROCK BASED ON NUMERICAL SIMULATION

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2009, 28 (S1): -3137 doi:
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The similarity model experiment is carried out to simulate the whole process of damage development of roof of metal mine laneway falling from stability. Fiber Bragg grating sensors installed in bolt are used to record the response signal of complete roof and damage roof under different confining pressures and different vibration intensities，and wavelet transform is utilized to extract vibration response signal of the band energy distribution characteristics. Finally，according to the result of the indoor experiment，the monitoring time series is predicted using radial basis function(RBF)；based on the view of energy band，the transient signal evaluation system under different damage conditions is established using software Matlab；and a serial of continuous signal are analyzed. The vibration response signal energy of damage roof is influenced by developed fracture. Compared with the complete roof，there is an obvious band cusp that the energy peak moves from high frequency to low frequency. Based on roof stability analysis method of wavelet frequency band energy，attenuation degree of wavelet decomposed frequency band energy is considered as the distinction that roof is stable or not. The frequency band energy ratio and the normalized energy ratio are used to determine the degree of damage and fracture state，which provides a reliable method for stability monitoring of laneway roof in metal mine.

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RECENT DEVELOPMENT IN NUMERICAL SIMULATION OF HYDRAULIC FRACTURING ON CORE WALL OF EARTH-ROCK FILL DAM

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2009, 28 (S1): -3146 doi:
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[PDF 152 KB] (983)

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The achievements in numerical simulation of hydraulic fracturing on core wall of earth-rock fill dam are summarized in detail，which include the recent development in China and abroad. Main achievements are listed as follows. (1) Numerical analytical methods include the total stress method and the effective stress method based on the consolidation theory of saturated soil，which are routine methods for numerical analysis of hydraulic fracturing on the core wall of rockfill dam，while the effective stress method based on the consolidation theory of unsaturated soil is a new one. (2) It is more reasonable to use the total stress method to judge the hydraulic fracturing on the core wall than the effective stress method. (3) The numerical analytical methods promote the study of the influential factors of hydraulic fracturing on the core wall.

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STUDY ON MECHANICAL PROPERTIES OF RHYOLITE UNDER LOADING AND UNLOADING CONDITIONS IN NIBA MOUNTAIN TUNNEL

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2009, 28 (S1): -3150 doi:
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[PDF 269 KB] (935)

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To provide references for stability analysis of Niba mountain tunnel construction，based on the actual stress environment and the uniaxial compression test，a series of triaxial compression and unloading tests are carried out. The rhyolite specimens are sampled from deep boreholes. The complete stress-strain curves of rhyolite specimens are analyzed and contrasted under different conditions，and the following results have been drawn. Microcracks develope in deep-buried rock mass. With the increase of buried depth，the peak strength becomes higher gradually. Integral rhyolite specimens have high compression strengths and obvious brittleness. Under triaxial compression conditions，the rhyolite specimen has obvious yield character，but macro failure happens after large plastic deformation. The failure forms turn from splitting failure to shear failure with the confining pressure increasing，and the obliquity of the fracture plane becomes gentle. Under unloading condition，the rhyolite specimens will be damaged more easily；the cohesion c is 48% lower than that under conventional compression condition，while internal friction angle  is 11% greater than that under conventional compression condition.

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STUDY ON DEFORMATION OF LOESS SLOPE UNDER CYCLIC LOAD

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2009, 28 (S1): -3156 doi:
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[PDF 268 KB] (937)

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By collecting loess samples in typical slope along Zhengzhou—Xian passenger special line，the dynamic shear strength and dynamic stress-dynamic strain relationship of Q3 loess acquired by loess undrained dynamic triaxial test under cyclic load are discussed. The results show that with the increase of cycle number，the strain of Q3 loess develops. When the dynamic load is less than preliminary consolidation pressure，the dynamic strain increases in several initial cycles，and strain rate decreases after cycle number with that strain curve becomes flat；once exceeding preliminary consolidation pressure，the strain increases rapidly and eventually leads to soil damage. Dynamic elastic modulus with increasing strain gradually decreases，and this relationship can be described as hyperbolic form. The dynamic shear strength lower than static shear strength decreases with cycle number. Based on these results，the loess slope dynamic model is established，and the slope deformation rules are studied. The rules show that the instability process is an unstable one as stress，displacement，velocity and acceleration of slope change with time. The lower slope has great displacement and becomes instable more easily than the corresponding upper one. Subjected to train vibration load，the dynamic shear strength of loess decreases，which leads loess slope stability to decrease. Compared with the upper slope，the lower slope is apt to be instable easily.

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FINITE ELEMENT SIMULATION OF COLLAPSE AND SLIDING OF SLOPE WITH SINGLE WEAK PLANE INDUCED BY STRONG EARTHQUAKE

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2009, 28 (S1): -3163 doi:
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[PDF 243 KB] (981)

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Based on the characteristics of collapse and landslide induced by Wenchuan earthquake that the quantity，the distribution density and the influential area，etc. are large，the damage mechanism of the complex structural slope is analyzed under strong earthquake，and the different stress-strain curves of some points in slope are given under microseism and strong earthquake. It is pointed that slope will generate additional stress under the effect of earthquake. The superposition of the additional stress and the original stress forms the total stress. When the total stress is larger than the tensile strength of the rock，tensile fracture occurs. The tensile fracture criterion is given. The finite element method is used to simulate tensile fracture process of slope with single weak plane under strong earthquake. The following conclusions can be drawn. When the first principal(tensile) stress is greater than or equal to tensile strength of rock，it cracks and can not bear tensile stress but compressive stress；if the total stress state meets the plastic yield criterion，shear failure occurs；the tensile fracture region cumulates continuously during earthquake dynamic，that is，the loose degree and the loose range become increase；and the slope containing weak plane can easily crack along the weak plane under earthquake.

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RESEARCH ON SEISMIC RESPONSE OF SOIL-ROCK MIXTURE SLOPE BASED ON ADDED MASS

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2009, 28 (S1): -3168 doi:
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Based on added mass method，using the powerful function of secondary development of ABAQUS，the stability of a soil-rock mixture slope on the left bank of Liyuan hydropower station on midstream Jinsha River is analyzed under the condition of earthquake after impounding. The results show that：(1) during the whole process of earthquake，both the value and the direction of the moving velocity of geomaterial change sharply，and this kind of repetitive variation may be one of important reasons that geological bodies loose their stability；(2) the enormous seismic shock wave makes shallow part of the slope mass move outside，but the motion direction of geomaterial under water level is mainly horizontal while other parts mainly move in vertical direction because of the reservoir water pressure；and (3) although the slope shows different plastic yields under seismic condition，continuous plastic zone does not come into being. So it can be inferred that the slope still keeps stable under seismic condition.

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RESEARCH ON SHEAR CREEP PROPERTY OF TYPICAL WEAK INTERCALATION IN REDBED SOFT ROCK

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2009, 28 (S1): -3176 doi:
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Weak intercalation in redbed soft rock has the property of creep. Most of slope rock masses destabilize along the weak intercalation. So the selection of shear strength parameters is a key problem in the survey of slope. The shear creep experiments on samples with weak intercalation collected from two typical redbed soft rock slopes are performed. The results show that the soft intercalation is very significant in creep，which should be considered in the shear strength parameters. According to the analysis of long- and short-term shear strengths，it is suggested that the long-term shear strength is about 75% of short-term one.

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COMPARATIVE STUDY ON APPLICATION OF CABLES AND FINISHING ROLLING STEEL BOLTS TO LANDSLIDE TREATMENT

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2009, 28 (S1): -3181 doi:
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There are two opinions of using finishing rolling steel anchor and prestressed steel strand cables in landslide supporting-retaining structure. One considers that finishing rolling steel anchor has higher anticorrosive performance and longer serviceable life than those of prestressed steel strand cable，while the other thinks that prestressed steel strand cable is more convenient because of its advantages of technical maturity，covenant construction and low cost，although the prestressed steel strand cable is prone to corrosion failure under the condition of long-term immersion of water in reservoir. The performance and the price of finishing rolling steel bolt and prestressed steel strand cable are compared by field experiments. The results provide useful data for the utilization of finishing rolling steel bolt and prestressed steel strand cable in geological hazards treatment.

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RESEARCH ON INFLUENCE AND MONITORING OF SHIELD TUNNEL OBLIQUELY CROSSING BENEATH EXISTING SUBWAY STATION

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2009, 28 (S1): -3186 doi:
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[PDF 309 KB] (1157)

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The influence of existing subway station on the construction of beneath oblique shield tunnel is analyzed based on engineering case. At the same time，the key construction parameters are researched by the analysis of construction parameters and monitoring data of structure deformation. By the analysis of monitoring data，the rule of structure deformation is obtained. It is useful reference for similar projects in future.

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STUDY ON TOPPLING DEFORMATION AND FAILURE CHARACTERISTICS OF STEEP BEDDING ROCK SLOPE

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2009, 28 (S1): -3193 doi:
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Bedding rock slope is one of the common slope types. The intensive studies have been done for its slope deformation，failure characteristics and formation mechanism. Generally，it is believed that slip-rupture and slip-bending are main characteristics of deformation and failure of bedding rock slope. Through the collection of systemic references and great amounts of location investigation，it is found that there is another typical form of deformation and failure for steep bedding rock slope，namely，toppling deformation. Combining the typical engineering cases of steep bedding rock slopes with deformation and failure characteristics，the geological conditions and the deformation and failure characteristics of this kind slope are summarized and analyzed. Based on these studies，it is shown that in the process of valley evolution and slope-formation and under the maximum principal stress at the foot of slope，which is parallel to slope，rock stratum bends from top to bottom as a cantilever beam，finally its root will be broken off，and a toppling body comes into being. When the maximum shear stress is greater than the shear strength in the snapped zone of the slope，it will slip and landslide happens.

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CENTRIFUGE MODEL EXPERIMENTAL STUDY ON ACTIVE EARTH PRESSURE OF ANISOTROPY SANDY SOILS

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2009, 28 (S1): -3201 doi:
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[PDF 370 KB] (865)

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Centrifugal model tests on Nanjing micaceous sand in both vertical and horizontal orientations are conducted. The distribution of earth pressure is recorded by the pressure transducers，and the soil displacements are obtained by the new image-analysis-based displacement-measurement system(GIPS). The effect of anisotropy and deformation of sand soils are investigated by comparing the earth pressure distribution recorded by the tests and that calculated by theoretical formula of isotropic sand soils，also by comparing the sliding surface of the backfill with those of horizontally and vertically orientated micaceous sands. The results show that the earth pressure acting on the retaining wall decreases，and the displacements of the backfill increase when the retaining wall moves away from the backfill. The sliding surface gradually appears with the increasing displacements of the backfill. The backfill reaches active limit state when the displacement of the retaining wall gets to 0.001H(H is the height of sample model). The sliding surface of the backfill of horizontally orientated micaceous sand is steeper than that of the backfill of vertically orientated micaceous sand.

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EXPERIMENTAL RESEARCH ON DISINTEGRATION OF LOESS

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2009, 28 (S1): -3207 doi:
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[PDF 460 KB] (1444)

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By the field tests as well as tests conducted on the self-developed disintegration instrument，the disintegration of loess is studied. Results show that the disintegration procedure includes fragmentation process， breaking process，and separation process. Firstly，the characters of the three processes are generalized. The point of view is put forward that both the fragmentation process and the breaking process are instantaneous and non-reversible，while the separation process takes some time and is reversible to some extent. Secondly，the mechanism of influence of natural water content and loess structure on the disintegration are analyzed，which suggests that the time effect of the loess disintegration is caused by the velocity of humidification. That is，the disintegration process goes more quickly with the increase of natural water content of the loess，resulting in the thickening of water film surrounding the particles as well as the decrease of the swelling energy. Finally，the boundary effects of disintegration are mainly studied. Results show that the origin of the disintegration nucleus is the slow moistening of the penetration process of the inner layer caused by the temporary boundary confining of the outer penetration layer. Results obtained from the field tests indicate that the boundary effect becomes more obvious with the decrease of the depth of water and the increase of curvature of the slot surfaces，and the sharpening of the edges of the convex upright field samples. The reasons of finiteness and edging effects of disintegration are explained logically.

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BACK ANALYSIS AND NUMERICAL SIMULATION OF EARTH PRESSURE AROUND PILE-ANCHOR SUPPORTING STRUCTURES IN DEEP PIT

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2009, 28 (S1): -3214 doi:
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[PDF 351 KB] (1036)

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To get the actual value and distribution pattern of earth pressure acting on the supporting structures in deep pit，a method for earth pressure back analysis using in-situ monitoring data is proposed. The procedures and formulas for back analysis of earth pressure have been derived. Utilizing the in-situ monitoring data from a typical project in Beijing，the lateral earth pressure has been obtained. Comparison between the measured and the calculated values of earth pressure shows that the proposed method is reasonable and reliable. Furthermore，numerical simulation with FLAC has been conducted；and the comparisons among the measured，the calculated and the simulated values of moment in retaining piles show this method is reasonable and meaningful. The reliability of the method has been verified more.

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INFLUENCE OF EXISTING SUBWAY LOAD ON GROUND SETTLEMENT INDUCED BY UNDERGROUND EXCAVATION OF BEIJING SUBWAY DIAMETER LINE

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2009, 28 (S1): -3221 doi:
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[PDF 342 KB] (879)

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Using commercial finite difference numerical simulation software FLAC3D，the ground settlement induced by underground excavation of subway diameter line between Beijing Station and Beijing West Station is studied. According to the geological exploration data，a typical section of pile-in-hole method is selected to build computing model. And the effect of existing subway load and specific construction management are considered in the calculating conditions. Moreover，computing schemes and steps are designed based on these. According to the calculating results，the ground settlement induced by the existing subway load and the underground excavation is analyzed，and the relations and variation rules among settlements of tunnel，existing subway and ground are studied at the same time. Simultaneously，feasibility of diameter line construction is validated，which provides data supporting and references to specific technology improvement for subsequent construction.

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SEEPAGE CONTROL EQUATION OF COALBED METHANE IN GEOPHYSICAL FIELD AND ITS NUMERICAL SOLUTIONS

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2009, 28 (S1): -3226 doi:
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[PDF 442 KB] (790)

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To research reservoir and enrichment capacity influenced by seepage capability of original coalbed methane under ground in geophysical field，gas seepage equations under the influence of stress-temperature are deduced based on gas equations of continuity，PVT，adsorption，and seepage. The equations reflect the influences of geostress and ground temperature on pressure，content，permeability of coalbed methane. The stress and temperature affect gas pressure and change gas adsorption content，meanwhile，they affect gas pressure and coal porosity and change gas free content. In addition，the temperature affects adsorption parameter b and changes adsorption content. Under different combinations of the stress and temperature，there are different changing mechanisms of permeability. Initial rock stress based on Kaiser method，methane adsorption at different temperatures and seepage flow at different stresses and temperatures are tested. Meanwhile，porosity，ash，water and fugitive constituent of coal samples are measured. Adsorption experiment indicates that the adsorption parameter a does not obviously change with the temperature，and b decreases with the temperature increasing. Gas permeability in coal changes in contrary modes under different temperatures and stresses，namely，it increases with the temperature increasing at low effective stress，but reduces at high effective stress. Based on laboratory experiment and geological data，one- and two-dimensional numerical solutions of gas seepage equation in geophysical field are provided in finite difference method. The results indicate that the loss amount of coalbed methane is very little because of the present seepage flow in the study area. Low permeability coal seam has advantage of reservation and enrichment，but goes against late exploitation. Pressure releasing and temperature rising are effective ways of improving drainage efficiency.

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STUDY ON DAMAGE EVOLUTION AND ACOUSTIC EMISSION CHARACTER OF COAL-ROCK UNDER UNIAXIAL COMPRESSION

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2009, 28 (S1): -3234 doi:
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[PDF 205 KB] (1053)

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In order to study the deformation and damage character under load and to further reveal the evolutionary process and the time effect mechanism of coal-rock，damage evolution and acoustic emission(AE) character of coal-rock under uniaxial compression are studied using MTS815 servo-controlled rock mechanical test system and 8CHS PCI–2 AE system. AE character of coal-rock under uniaxial compression is analyzed. A new damage variable，which is defined based on normalized cumulative ring-down count of AE，is proposed；and the damage model of coal-rock under uniaxial compression is established. Damage evolution curve and equation of coal-rock are obtained. The results show that AE information can reflect internal damage of coal-rock and is closely related with primary crack compression and evolutionary course of new crack generation，growth，and connectivity. AE can describe the deformation and damage evolution character of coal-rock. The new damage model of coal-rock under uniaxial compression is reasonable；the deformation and damage evolution process can be divided into three phases including the stage of initial damage，the stage of damage stable evolution and development，and the stage of damage accelerating development. The development of coal-rock deformation and damage can be regarded to be gradual，which is the whole process from deformation and damage initiation and evolution to the appearance of macroscopic cracks，from macroscopic propagation to damage.

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ELASTOPLASTIC DAMAGE CONSTITUTIVE MODEL OF LOESS

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2009, 28 (S1): -3239 doi:
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[PDF 165 KB] (928)

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Based on the theory of thermodynamics and continuum damage mechanics and the energy conversion of loess in load and moistening，the definition of the loess moistening damage variable is put forward，as well as the equivalent energy index of loess moistening damage，which is related to the water content or the saturation degree to describe the moistening damage evolvement procedure. Based on the concept of J. C. Simos energy index，the energy index of loess load damage is presented. The structure breakage and degradation of mechanic and strength index are analyzed；and the evolvement procedure of loess load damage is given. To join with ellipse yield function and associated flow law and damage theory，in which hardening parameter is plastic work，the elastoplastic damage constitutive models of loess are derived.

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EXPERIMENTAL STUDY ON TIME-DEPENDENT PROPERTIES AND PORE WATER PRESSURE OF SOFT SOIL UNDER UNLOADING

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2009, 28 (S1): -3244 doi:
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[PDF 267 KB] (977)

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Using standard stress path triaxial system，STDTTS+UNSAT(7 kN/1 700 kPa) production of GDS，UK，a series of laboratory tests are conducted with undisturbed muddy clay samples obtained from Shanghai. Time-dependent properties and pore water pressure in passive zone and active zone in excavation are researched. It is shown that three stages appear under unloading：weakening stage，constant speed stage and accelerating stage. Creep curve is in weakening stage when unloading is small and then changes from weakening stage to constant speed stage with the increase of unloading. Soil sample is damaged quickly at high unloading stress level with deformation sharply increased. However，it is not found that creep curve of soil changes with time from constant speed stage to accelerating stage directly. Parameter of pore water pressure is not constant and changes with time. Pore water pressure decreases under unloading whether in passive zone or in active zone of excavation，then increases to the maximum value in undrained creep stage and safety ratio is the smallest at this time.

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LIMIT EQUILIBRIUM METHOD BASED ON RATIO OF FACTOR OF SAFETY FOR SLOPE STABILITY OF UNSATURATED SOILS

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2009, 28 (S1): -3250 doi:
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[PDF 188 KB] (714)

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The relationship between the factor of safety of unsaturated soils slope and the stability is proposed for a given unsaturated soil slice. If the minimum factor of safety is greater than or equals to the allowable factor of safety，the slice is safe. The general limit equilibrium methods for stability analysis，Swedish slice method and Bishop method，are conducted based on the ratio of factor of safety and the improved Mohr-Coulomb failure theory. Several special formulas are achieved when the pore pressure is 0. The minimum factor of safety of an unsaturated soil slope is analyzed with the changes of different parameters. Some results show that with the increase of the ratio of factor of safety，the minimum factor of safety significantly decreases，yet the density has little effect on the minimum factor of safety.

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RESEARCH ON JOINT SIMPLIFIED MODEL AND EFFECTS OF JOINT PARAMETERS ON PANEL STRESS AND JOINT DISPLACEMENTS OF FACED ROCKFILL DAM

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2009, 28 (S1): -3257 doi:
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STABILITY ANALYSIS OF BORROWED SOIL IN FINITE-LENGTH ECOLOGICAL SLOPE

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2009, 28 (S1): -3264 doi:
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[PDF 294 KB] (731)

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The mechanical stability of substrate(borrowed soil)，which is needed for plants，is crucial to ecological slope engineering. In the initial time of ecological slope engineering，the stability of borrowed soil is mainly dependent on its characteristic of anti-sliding. In general，the length of borrowed soil is not long enough compared with its thickness. To aim at solving the sliding problem of the finite-length slope by using model test and upper-bound solution，the test results show that the upper part of the failure plane is straight，which is set along the top surface of metal gauze and parallel with original slope surface，but the lower part is a curved-failure plane connected with the upper-part smoothly and passes through the upper border of retaining structure. The longer the slope is，the smaller slope angle will be when failure occurs，which also means more easily it will fail. Based on the results of model test，the failure mechanism and velocity field are proposed；and the upper-bound solution is given and verified.

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APPLICATION OF DATA FUSION ALGORITHM TO SAFETY EVALUATION OF PILE-GROUP FOUNDATION OF SUTONG BRIDGE

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2009, 28 (S1): -3270 doi:
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[PDF 254 KB] (845)

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Sutong Bridge located in the tidal reach adopts the pile-group foundation with large-diameter and over-length bored piles working with the steel casing together. Therefore，extensive angle monitoring is adopted to observe the structure response of steel casing，reinforcing steel bar and concrete. Because the sensors of different types and various locations have different working principals，precisions，installing and embedding manners and influence factors，the types and characteristics of measured data have great differences. So，multi-sensor information fusion technology is used to filter abnormal values，extracting characteristic information and constitute integrative decision．However，the observed data of prototype contain the strong noises caused by environmental factors such as the tide，which seriously interferes the analysis and forecasting of data. Furthermore，this type of noise would make the measured data bring about anomalous process and anomalies group，which is difficult to be detected through the redundant information and spatiotemporal contrast of the measured data. On the basis of data detection according to fusion algorithm and gross errors rejection，with the help of wavelet threshold denoising method，the noises caused by a single sensor are further eliminated gradually. According to the credibility and importance for the observed results from different types of sensors，the measured data from multi-sensor after denoising are fused based on the data fusion algorithm of optimal weight distribution principle. The practice has proven that the wavelet layered denoising technology can be used to effectively separate different noises；and the observed data offered by various sensors can be combined in phase by making use of multi-sensor data fusion technology，so that the stress response of pile-group foundation of Sutong Bridge and the surrounding environment can get a more reliable judgment.

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THREE-DIMENSIONAL SEEPAGE-STRESS COUPLING ANALYSIS OF
BRIDGE FOUNDATION BEHAVIORS INDUCED BY PRECIPITATION

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2009, 28 (S1): -3277 doi:
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The safety of the bridge and its normal operation are possibly influenced when the deformation of bridge foundation is largely induced by ground consolidation and the groundwater table in the stratum under the bridge foundation is lowered. In order to predict safety and deformation of bridge foundations during precipitation，3D non-saturation seepage-stress coupling theoretical analysis model is set up；and the 3D FEM model of interaction of ground，groundwater and bridge is also set up by software ABAQUS. Based on the direct coupling analysis method，spatial responses of bridge foundations during precipitation and the dynamic changes of groundwater table are simulated. It is discovered that ground settlement is 21.37 mm and bridge foundation settlement is 19.56 mm；and differential settlement between bridge foundations is less than 2 mm under the condition of descending 10 m water table. It is also proven that the bridge foundation is safe and the existing precipitation scheme is reasonable. The simulated and measured settlement values agree well. So it is demonstrated that numerical model and analysis method are reasonable and reliable，and it can offered important guidance and reference to the study of similar problem.

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EXPERIMENTAL RESEARCH ON MACRO-MESO CONSOLIDATION MECHANISM OF SANDY SOIL WITH DYNAMIC COMPACTION

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2009, 28 (S1): -3282 doi:
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[PDF 737 KB] (932)

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A fundamental understanding of the macro-meso mechanism of dynamic compaction of sandy soils using a modified visible model test apparatus，which is designed by authors，is carried out. A series of model tests of dynamic compaction are conducted on sandy soil with a new technique for real-time visualization and photographing；and soil displacement and dynamic stress are monitored for each case. The experimental results show that the technique can be used successfully to visualize the meso-scale change of sand grains fabric including orientation and average coordination apart from displacement. It is found that the optimum hitting number of each pass is about 8 for sandy soils；and the macro-mechanical results of dynamic compaction are the increase of ground displacement and decrease of void ratio；and the meso-scale mechanism is the process of grains rearrangement from disorder to orientation and increase of average coordination. The findings of this study will be beneficial to the innovation and determination of parameters for dynamic consolidation and the research of macro- meso response under impact loading.