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2009, 28 (05): -0 doi:
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STUDY OF CRITICAL CONDITION OF BOREHOLE INSTABILITY IN GRANITE UNDER HIGH TEMPERATURE AND HIGH PRESSURE

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2009, 28 (05): -865 doi:
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Utilizing the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure developed by the authors and using optical observation instrument of borehole deformation made by theory of optics，the intensive study of deformation laws and instability critical conditions of large-size granite with f 40 mm borehole samples of f 200 mm×400 mm within 600 ℃ and triaxial hydrostatic stress in depth of 6 000 m is carried out. The research results are as follows：(1) The deformation of borehole in granite bored with the increase of temperature and stress performance is obvious at different stages with high temperature and high pressure. Within hydrostatic stress of 4 000 m in depth and temperature at 400 ℃，drilling performance is obvious at the moment of viscoelastic stage. Although borehole diameter reduces but still in stable condition，and damage does not occur. The hydrostatic stress of 4 000–5 000 m in depth and the temperature at 400 ℃–500 ℃，the deformation of borehole is at viscoelastic-plastic stage and the surrounding rock near drilling shows a destructive trend，and the aperture begins to increase. Under 5 000 m hydrostatic stress in depth and temperature more than 500 ℃ when the cracked rock-like particles block in plastic zone gradually fall down from the hole wall，the borehole is in damage. (2) When the surrounding rock of granite in more than creep threshold of stress and creep threshold of temperature，which is over hydrostatics stress of 5 000 m in depth and temperature than 500 ℃，the borehole is in destruction and the collapse of a borehole phenomenon occurs. At the same time，the particles of surrounding rock in granite are falling down；and the hole diameter is increasing. (3) At different temperatures and hydrostatic stresses in depths，the critical hydrostatic stress of rheodestruction of surrounding rock is 5 000–6 000 m (that is 125–150 MPa)；and the critical temperature of rheodestruction is 500 ℃–600 ℃. The failure modes are of compression fracture，transpression or both of them. (4) The critical condition of borehole instability in granite under high temperature and stress is hydrostatic stress of 4 000–5 000 m in depth and temperature at 400 ℃–500 ℃. These research can provide a scientific basis and theoretical guidance for hot dry rock(HDR) development to utilize the drilling in the maintenance of stability and Chinese continental scientific drilling(CCSD) in the aspect of ultra-deep hole and deep hole in the construction of drilling encountered in the process of stability.

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MODEL STUDY OF THREE-DIMENSIONAL GRANITE CREEP PROPERTIES UNDER HIGH TEMPERATURE

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2009, 28 (05): -875 doi:
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By making use of the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure of China University of Mining and Technology，the experimental studies of creep properties of large-size granite specimens of f 200 mm×400 mm with temperature up to 600 ℃ and axial stress up to 175 MPa are carried out. This research reveals：(1) Under three-dimensional stress，the axial creep deformation at 300 ℃ and 500 ℃ and volumetric creep deformation at 300 ℃，500 ℃ and 600 ℃ of Lu Gray granite show three stages：primary creep stage，stable-state creep stage and accelerating creep stage. (2) Under high temperature and 3D stress，the volume，length and radius of Lu Gray granite increase with time because of fissure caused by thermal cracking in rock. The lateral deformation was more rapid than axial deformation at the same time. (3) It¢s the basic hypothesis of visco-elastoplastic problem under three-dimensional stress that differential stress causes axial creep；hydrostatic stress causes volumetric creep deformation based on experimental data；and the volumetric creep constitutive equation of Burgers model under three-dimensional stress is also proposed. (4) Through the analysis of creep curve，it¢s proper to simulate axial creep at 300 ℃ and 500 ℃ and volumetric creep at 300 ℃，500 ℃ and 600 ℃ with Burgers model and to calculate model parameters.

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IN-SITU TEST STUDY OF CHARACTERISTICS OF ROLLING ROCK BLOCKS BASED ON ORTHOGONAL DESIGN

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2009, 28 (05): -882 doi:
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Site experiment of rolling rock was designed in terms of the design theory of orthogonal test，of which 6 influential factors were considered including onset style of rolling rock，feature of overburden and vegetation，gradient of slope，length of slope，shape of rolling rock and mass of rolling rock. And these 6 influential factors were analyzed with the experiment by means of range，variance and regression analysis. During the analysis，the evaluation criteria were the acceleration of rolling rock movement and the restitution coefficient of collision velocity between rolling rock and slope surface. It is shown that among so many influential factors of acceleration，the gradient of slope is the most important one，followed by shape of rolling rock，feature of overburden and vegetation，length of slope，mass of rolling rock，onset style，in turn. The gradient of slope，the shape of rolling rock and feature of overburden and vegetation are critical factors for the movement velocity of rolling rock. The movement acceleration of rolling rock has a linear correlation with those above critical factors. Among 6 influential factors，only the feature of overburden and vegetation play an important role of controlling the restitution coefficient of rolling rock，which can be expressed by a linear relation. To the prevention of potential unstable rock mass，these experiment results provide proof to determine the impact energy. New feasible method is put forward for the whole treatment of potential unstable rock mass，which has a practical significance to the prevention of slope geohazard.

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EXPERIMENTAL STUDY OF EFFECTS OF CYCLIC LOADING AND UNLOADING PORE WATER PRESSURES ON DEFORMATION
CHARACTERISTIC OF SANDSTONE

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2009, 28 (05): -892 doi:
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Triaxial compression experiments have been carried out to study the effects of the cyclic loading and unloading pore water pressures on the deformation characteristic of saturated sandstone when the axial stress and confining pressure are invariant using the MTS815 rock mechanics testing system. The experimental results have shown that there are anomalistic Z-shaped nonlinear wave in the stress-strain hysteresis curve at the stage of compaction under loading and unloading；and initial residual deformation is relatively large，therefore，the hysteresis loop is not so obvious. In addition，it has been observed that at the elastic coupled stage，the stress-strain curve which rises with concave Z-shaped wave appears inflection point before coming to a head；at this point，strain is the maximum at loading. While at unloading，it is inflexion at the stress-strain curve which drops with convex Z-shaped wave before touching bottom；at the same time，the strain fetches the minimum. Meanwhile the stress-strain hysteresis loop，showing the stage from sparse to dense，is stable which indicates evolution from elastic deformation to plastic deformation. The dissipation energy of different upper limits and different amplitude areas forms into asymmetrical X-shaped at the pore water pressure. The dissipation energy decreases gradually at loading with the increase of pore water pressure. Otherwise，at unloading，it decreases gradually with reducing of pore water pressure. The position and angle of the X-shaped crossing are related to the different upper limits and amplitude areas. The relationship between the residual strain and cyclic numbers accords with the power of negative index under the cyclic loading and unloading pore water pressures.

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TUNNEL CONSTRUCTION MULTIVARIATE INFORMATION FOREWARNING AND SAFETY MANAGEMENT SYSTEM RESEARCH

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2009, 28 (05): -900 doi:
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This paper introduces multivariate information automatism collection，wireless transmission，forewarning，safety management，etc. and key technologies of TMIGS，and it uses wireless communication to combine three-dimensional laser scanning，personnel equipment orientation，all kinds of sensor data collection，communication video and safety management to realize tunnel construction face image collection，display，edit and analysis，and construction face stability monitoring and personnel orientation management. And certain tunnel measuring item and section scanning technology are combined to forewarn around rock distortion and exceed，lack digging，and all kinds of sensors of selected measuring section of wireless data collection and synthesis analysis are brought forward. While danger is approaching tunnel，TMIGS can compute，analysis，awake，forewarn and startup emergency plan class IV in advance to guarantee worker safety to maximum extent. TMIGS has an important meaning for dynamic design and general supervision，and it enhances safety degree in tunnel construction.

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TECHNOLOGICAL RESEARCH ON SAFETY EVALUATION OF PUMPING WELL APPROACHING TO HIGH CONFINED AQUIFER IN NORTH CHINA— A CASE STUDY OF XUECUN COALMINE IN FENGFENG MINING AREA

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2009, 28 (05): -908 doi:
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Lack of suitable norms or codes to observe made it difficult for scholars to evaluate hydrogeological conditions for safe advance of the pumping well approaching to high confined aquifer in Xuecun coal mine，Fengfeng mining area，the heavy water mining area. To solve the problem，the authors take advantage of pressure-tunnel model，key stratum theory，the relationship of permeability vs. strain and numerical simulation methods to evaluate the safety of pumping well approaching to the strong Ordovician limestone aquifers based on hydrogeological condition analyses. The same conclusions from all the above methods were drawn that the failure area is far away from the strong aquifer and the advancing engineering is safe. The authors considered that water inrush coefficients of floor strata given by the regulations were not suitable for pumping well in hydrogeological evaluation. Water inrush would not take place during the well advancing even though the inrush coefficient excesses the limit given by the regulations. The methodology given in the paper explored a way for pumping well safety evaluation in hydrogeology for North China typed coal mines.

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COMPARATIVE STUDY OF MODERN DIGITAL MULTIFUNCTIONAL CPTU AND CHINA¢S CPT TESTS

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2009, 28 (05): -914 doi:
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The development of cone penetration test(CPT) at home and abroad is introduced in brief；then the status of CPT technology at home and abroad is expounded. Various sizes and configurations of China¢s double bridge CPT and international piezocone penetration test(CPTU) on Jiangsu clays of China are summarized. According to the CPT and CPTU tests at five sites，parameters measured by the 10 cm2 CPTU are presented and compared to China¢s double bridge 15 cm2 CPT. It is shown that using the 10 cm2 CPTU rather than the 15 cm2 CPT can significantly improve the detection of thin silt layers within clay. The conversion relationship between China¢s double bridge CPT and international CPTU are developed for different soil types. Some conclusions and suggestions are finally put forward. The findings give us the potential use of 10 cm2 international CPTU in practice.

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ELASTO-VISCOPLASTIC CONSTITUTIVE MODEL OF SANDY SOIL CONSIDERING STRESS PATH AND LOADING RATE

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2009, 28 (05): -929 doi:
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Based on the experimental results of drained plane strain compression(PSC) on saturated dense sandy soil along a wide variety of stress paths，the effects of stress path and loading rate on the deformation and strength characteristics of sandy soil are investigated. It is found that the irreversible shear strain and irreversible volumetric strain are dependent on stress history and stress path. And significant loading rate effect is observed in the tests. The same as creep deformation and stress relaxation，loading rate effect should be attributed to the viscous properties of the sandy soil specimens. One of the most important characteristics of loading rate effect is the stress changes sharply with a very high stiffness，nearly elastic behavior，when the strain rate suddenly changes. Subsequently，the use of any quantity shown above as the hardening parameter is not well reasonable in the traditional plastic theory. Based on the analysis of these test results，a novel modified irreversible strain energy，Wir*，and the related function are shown to be stress path-independent. An energy-based elasto-viscoplastic constitutive model of sandy soil，described in a nonlinear three-component framework，is proposed with the use of Wir* as the hardening parameter. The presented model can take into account the effects of stress path，pressure level，inherent anisotropy，void ratio，work softening associated with strain localization into a shear band and loading rate effect on the stress-stain behavior. The finite element method code incorporating the presented model is validated by simulating the PSC tests. It is shown that the proposed model can much better simulate the effects of stress path and loading rate on the deformation and strength characteristics of sandy soil than the previous models.

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CENTRIFUGAL TESTS ON SLOPE REINFORCEMENT BY ANTI-SLIDING PILES MODELLING CHANGE OF RESERVOIR WATER LEVEL

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2009, 28 (05): -939 doi:
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[PDF 365 KB] (1198)

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Anti-sliding pile is one of the most effective measures for slope reinforcement. On the basis of centrifugal tests modeling the impoundment and cyclical change of water level in the Three Gorges Reservoir，this paper pays attention to the reinforcement mechanism of unstable reservoir slope by anti-sliding piles；and the corresponding test techniques of centrifuge modelling are introduced. A series of centrifuge tests including natural slopes and reinforced slopes with different pile layouts are conducted；slope displacement，failure modes and bending moments of piles are obtained during the testing procedure；the distribution of landslide pushing force，mechanism of pile-slope interaction and arching effect are discussed as well. Results indicate that the deformation of reinforced slope will still occur during the first stage of change of reservoir water level；it will be gradually controlled during the form of arching effect due to different soil displacements behind the piles. Moreover，the bigger the pile spacing is，the weaker reinforced effects are，which leads to the larger slope deformation. However，the maximum pile bending moment of each test shows parabolic character，so there must exist an optimal pile spacing under which the reinforcing effect will be the best. In addition，the pushing force acted on the anti-sliding pile obeys multi-triangle configuration. This study provides not only the direct data for the investigation of interaction mechanism between pile and slope，but also the new idea of optimal pile spacing for slope reinforcement design. It will contribute a lot to the theory of slope stabilization by piles and prevention of landslide disaster in the Three Gorges Reservoir area.

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COUPLED THERMO-HYDRO-MECHANICAL MODEL AND FINITE ELEMENT ANALYSES OF DUAL-POROSITY FRACTURED MEDIUM FOR UBIQUITOUS-JOINT ROCK MASS

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2009, 28 (05): -947 doi:
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[PDF 289 KB] (1299)

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A kind of coupled thermo-hydro-mechanical model of dual-porosity fractured medium for saturated- unsaturated ubiquitous-joint rock mass，in which the stress field and the temperature field are single，but the seepage field is double，and the influences of sets，spaces，angles，continuity ratios，stiffnesses of the fractures on the constitutive relationship of the media can be considered，is established；and also the relative two- dimensional program of finite element method is developed. Taking an assumed nuclear waste repository for example，in which two cases of rock mass including dual-porosity medium and single-porosity medium respectively are simulated；and the temperatures，pore pressures，saturations，flow velocities and principal stresses in the buffer and rock mass are investigated. The results show that water flows from the dual-porosity medium into the buffer are quicker by far；the difference of temperatures in the calculation domain of two cases is very small，but there are obvious variations in magnitudes and distributions of the principal stresses in the near field for the two kinds of media；and the stress concentration in the single-porosity rock mass is larger.

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STUDY OF CONSTITUTIVE EQUATION OF GRANITE RHEOLOGICAL MODEL WITH THERMO-MECHANICAL COUPLING EFFECTS

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2009, 28 (05): -956 doi:
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The change of rock microstructure with thermo-mechanical coupling effects is the main cause for transformation of macroscopic mechanics of rock. The rheological mechanism of granite with thermo-mechanical coupling effects；and rheological model of granite are researched. As a result，it is a kind of feasible way for building rheological constitutive equation. According to the research on rheological mechanism of granite with thermo-mechanical coupling effects，it knows：(1) Granite is a sort of brittleness and hardness rock constituted with multi-ingredient；it is provided with polycrystal multiple medium and prodigious anisotropic. Microstructure inside of granite can be divided into grain，boundary of grain，intercrystalline cement and intercrystalline pore；such ingredient and structure determine the rheological properties of granite with thermo-mechanical coupling effects. (2) The rheological phenomenon is induced by dislocation and cracking of grain and cement of grain with thermo-mechanical coupling effects，which is a compound rupture process with thermal cracking by temperature and damage cracking by stress. So macro-mechanical properties of mechanical parameters become a function of temperature. Therefore，the viscoelasto-plastic rheological elements of mechanical model combining the phenomenon of rock rheology and physical rheology are proposed；and the rheological model of granite with thermo-mechanical coupling effects on the basis of generalized Nishihara rheological model is constructed. The evolution model is deduced，which can describe 150 MPa and 600 ℃ granite within the evolution of the constitutive equation；and experimental results show its application and rationality. Granite model of the constitutive equation with thermo-mechanical coupling effects provides a basis for the establishment of high- temperature geothermal development drilling rock of stability.

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EXPERIMENTAL STUDY OF MECHANICAL BEHAVIORS OF SANDSTONE UNDER HIGH-PRESSURE OIL AND GAS RESERVOIR

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2009, 28 (05): -968 doi:
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Sandstone samples are selected by the compressive wave velocity and the shear wave velocity. Then test scheme has been designed to simulate rock mechanical behaviors under the altering pore pressure of high- pressure oil and gas reservoir according to the geological structure. All the triaxial tests have been performed on the triaxial compression test system GCTS–1000 with high temperature and high pressure. The test results show that：rock strength doesn¢t increase monotonically with confining pressure while the internal pore pressure is increasing and confining pressure keeps constant；but the rock strength will decrease with the net increasing confining pressure first and increase abnormally then. The minimum value appears when the geostress gradient is equal to 2.20 MPa/(100 m)；but the sandstone compressive strength grows up with the increase of geostress gradient. The relationship curve between rock strength and pore pressure is V-shaped. The relationship curve between elastic module and pore pressure appears as a wave shape and the maximum difference among elastic module is 2 909 MPa. In the experiment，the Poisson¢s ratio increases gradually and approaches 0.5 when the geostress gradient coefficient is larger than 2.00 MPa/(100 m). This particular phenomenon of sandstone triaxial strength has been observed during repeated tests. The test result is significant to simulate the true three- dimensional deformation and failure of the system composed of high-pressure gas and oil reservoir，cement sheath and casing.

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ONE-DIMENSIONAL CONSOLIDATION THEORY OF SATURATED CLAY BASED ON NON-DARCY FLOW

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2009, 28 (05): -973 doi:
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There sometimes exits notable difference between the solution of one-dimensional consolidation of saturated clay layers based on Terzaghi¢s theory and the field settlement observations，which can be in a certain extent ascribed to that the flow of pore water in these soil layers may not obey Darcy¢s law. In order to improve the precision of consolidation computation，Terzaghi¢s one-dimensional consolidation theory is modified based on the non-Darcy flow described by the power function for the lower velocity of flow and the linear function for higher velocity of flow，and the numerical analysis is performed using the finite volume method. In order to verify its validity，the numerical solution by the present method for the case that the flow of pore water obeys Darcy¢s law is compared with the analytical solution based on Terzaghi¢s one-dimensional consolidation theory. Then the effects of the parameters of non-Darcy flow on the consolidation process are investigated. The numerical results indicate that the non-Darcy flow delays the dissipation of pore water pressure in saturated clay layers；thereby the consolidation velocity of these soil layers is smaller than the solution based on Terzaghi¢s theory. Besides the coefficient of consolidation，a new parameter I1 composed of the threshold hydraulic gradient i1，the thickness of soil layer H and the vertical uniform load p0 is introduced to characterize the consolidation of these soil layers. Finally，the applicability of Terzaghi¢s one-dimensional consolidation theory is discussed.

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STUDY OF TEST METHOD OF GEOMECHANICAL MODEL AND TEMPERATURE ANALOGOUS MODEL MATERIAL

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2009, 28 (05): -980 doi:
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SIMULATION OF CLAY AQUIFUGE STABILITY OF WATER CONSERVATION MINING IN SHALLOW-BURIED COAL SEAM

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2009, 28 (05): -987 doi:
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According to the complete stress-strain curve test of clay aquifuge，a new simulation method is put forward considering the peak strain and strength as well as residual strength and strain. Through series of material proportion tests by use of the single-factor analysis method，the aggregate materials and proper agent for materials are obtained；and the proper material proportions are advanced for the complete stress-strain simulation of clay aquifuge. Through the simulation tests of longwall mining of Yushuwan coalmine，the caving feature and subsidence movement of bedrock roof and clay aquifuge of overburden are presented. It is shown that the roof pouring water of mining face is from weathering layer rather than ground surface，which is proven by mining practice. It is also found that there is a main subsidence area behind mining face；and the clay aquifuge trends to lose stability in this area. The subsidence gradient Ts of this area is the key index for aquifuge stability control；and to decrease the Ts or increase the subsidence span is the effective approach of aquifuge stability control. This simulation shows that the water conservation mining can be realized in Yushuwan coalmine；and this research provides a method for water conservation mining in shallow-buried coal seam.

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A COUPLED ELASTOPLASTIC DAMAGE MODEL FOR
GAS-SATURATED COAL

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2009, 28 (05): -993 doi:
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Under triaxial compressive conditions，with an increase of loading，the propagation and sliding of microcracks in rocklike materials become increasingly intense and lead to a serial of consequences，such as nonlinear stress-strain relationships，deterioration of elastic modulus，anisotropic deformation，volumetric dilatancy and irreversible plastic strain，etc.. These phenomena may be described by continuum damage mechanics and plastic theory. Firstly，in order to take into account the effect of gas adsorption，the swell stress of gas adsorption is introduced into the effective stress principle of porous media；and the effective stress formulation for gas-saturated coal is derived. Anisotropic damage with plasticity yield criterion and damage criterion are introduced to be able to adequately describe the plastic and damage behavior of gas-saturated coal. Damage evolution law and the coupling between plastic deformation and damage are represented using the framework of irreversible thermodynamics. On the basis of the experimental results，a general coupled elastoplastic damage constitutive model is developed for the mechanical responses of gas-saturated coal under various loading conditions by adopting a non-associated plastic flow rule. The comparison between experimental dada and their simulation equivalents is performed for gas-saturated coal under various stress states. It is obvious that the proposed model is able to effectively depict the main features of mechanical behavior observed in gas-saturated coal. At the same time，the proposed model is also suitable for constitutive description of other rocklike materials.

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CAUSE ANALYSIS OF LONGITUDINAL CRACKS OF ROCK-ANCHORED BEAM AND ITS DEVELOPMENTAL TREND IN UNDERGROUND POWERHOUSES

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2009, 28 (05): -1000 doi:
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After the completion of excavation of the 6th layer of the underground powerhouse，the longitudinal cracks appeared in the concrete upper surface of the rock-anchored beam. Monitoring data indicate that the width of the cracks in lower part between the concrete and the rock mass is larger than the upper one，which is an unusual phenomenon. Detailed cause analysis of these cracks was made based on the in-situ geological environment，monitoring data，constructional procedure and the numerical simulation. The analysis results indicate that the distance between the top of the bus gallery and the rock-anchored beam is only 5.2 m，and rock mass is cut by 3 weak interlayers. Due to the construction of the main machine hall，the ground stress was readjusted，and the obviously concentrated stress phenomenon appeared at the rock mass，which resulted in the non-uniform deformation of the rock mass. Numerical calculating results indicate that as the excavation goes on，the rock mass between the interlayer JC2–2 and the lower one has the trend to be squeezed out of the palisades，while this deformable body lies in the lower part of the rock-anchored beam，the widths of the cracks in lower part are larger than ones in the upper part，which explains the unusual phenomenon of the monitoring results. Simulation results also indicate that this value in cross section CZ0+87 is larger than that in cross section CZ0+127，which agrees well with the monitoring data. Finally，forecasting is made on the displacement development trend of cracks in the rock- anchored beam；and several advices are given.

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MECHANISM OF DEWATERING-INDUCED GROUND SUBSIDENCE IN DEEP SUBWAY STATION PIT AND CALCULATION METHOD

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2009, 28 (05): -1010 doi:
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Monitoring data in Yishan Road station deep pit，subway No.9，Shanghai，China with multiple position extensometers indicate that the subsidence caused by dewatering of confined water has different rules：the accumulative multi-layered settlement is not equal to ground subsidence and some strata are not compressed but expansive. The mechanism is explained by combination of high-lower seepage characters，dewatering in deep confined aquifer-inversed rebound of overlaying strata，consolidation from deep-coordination of deformation and gradual boundary. The subsidence caused by dewatering in deep subway station pit is calculated by the accumulation method of each layer according to specification. A modified calculation method is established. Firstly，the single point deformation and compression in each layer are defined according to the law of inversed rebound，supposing that the inversed rebound and consolidation appear simultaneously but can be calculated separately；and the inversed rebound is measured by inversed rebound index. And the gradual consolidation is considered by layer division. When the inversed rebound value is greater than consolidation one，the strata will expand. The ground subsidence can be precisely predicted by the method when the inversed rebound index and drawdown are measured or calculated reasonably.

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EXPERIMENTAL STUDY OF LOAD TRANSMISSION PROPERTY OF LARGE-DIAMETER BORED CAST-IN-SITU DEEP AND LONG PILE IN DIFFERENT SOIL LAYERS

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2009, 28 (05): -1020 doi:
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The load transmission property of large-diameter bored cast-in-situ deep and long pile in different soil layers under vertical load is analyzed on the basis of measuring data of static load test and pile stress measurement in Changzhou viaduct road project I. The test pile is loaded to destruction，which can supply valuable project reference to further studying bearing capacity of larger-diameter bored cast-in-situ long pile. The study indicates that the bearing capability of pile bottom in deep soil layer accounts for lower proportion than skin friction；and the Q-s curves of large-diameter bored cast-in-situ long pile show steep drop type，especially with a significant inflection point. Skin friction and tip resistance of the pile have mutual influence on each other and don¢t display simultaneously；and the same situation also exists in side friction in soil layer，which demonstrates that the above soil layer first reaches the limit state；and then the lower soil layer. Burying depth has significant influence on side friction of soil layers around pile which has similar physical mechanical property and some values about side friction have great difference to recommendation value of the reconnaissance report according to measuring data. The load transmission curves of soil layer (1) and soil layer (3) correspond to process-softening model，and the load transmission curves of soil around pile bottom correspond to bilinear rigid model，which demonstrates that side friction of above soil layers is weakened to some degree for the soil layers have tendency to be destroyed by shearing；and a great deal of tip resistance of the pile is not displayed under vertical load.

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ANALYSIS OF EFFECT OF SLURRY INFILTRATION ON SHEAR STRENGTH OF SOIL OF EXCAVATION FACE IN SLURRY SHIELD UNDER GENERAL STRESS CONDITION

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2009, 28 (05): -1027 doi:
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EXPERIMENTAL RESEARCH ON DYNAMIC CHARACTERISTICS
OF ROADBED COMPACTION LOESS

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2009, 28 (05): -1037 doi:
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Based on a lot of dynamic triaxial tests，some dynamic characteristics on roadbed compaction loess are studies. It is indicated that from test results，the relation between stress and strain can be fitted with hyperbolic model under certain conditions，and the values of model parameters are and tend to be stable gained on some soil samples. Dynamic modulus of compaction loess decreases with the increase of dynamic strain，the trend is basically similar under different dry densities，water contents and pressures. Damping ratio is affected by the moisture，consolidation stress ratio，confining pressure and dry density of the compacted loess which increases with the increase of dynamic strain generally；and its value is distributed in 0.2–0.3 with high discreteness. The value of vibration deformation has important relation with the dry density，moisture and load cyclic number. When the dry density increases，moisture decreases，and load cyclic number increases. It decreases slowly at the same stress conditions，and there is critical dynamic stress. When the dynamic stress is smaller than it，vibration deformation is small and can be fitted linearly with the dynamic stress，otherwise，it increases quickly and presents obvious non-linearity.

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DETERIORATION OF EARTHEN SITES AND CONSOLIDATION WITH PS MATERIAL ALONG SILK ROAD OF CHINA

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2009, 28 (05): -1047 doi:
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The numerous earthen sites along the Silk Road of China have different environmental conditions，whose deteriorations are mainly divided into two types in terms of their locations：the unsheltered ones suffering from wind and rain erosion and crevasses，and the sheltered ones suffering from the pollution，efflorescence and crevasses. This paper studies the consolidation and conservation of the Jiaohe Ruins in Turpan，analyzing the earthen samples taken before and after consolidation with PS materials by X-ray diffractometer，measuring the degrees of crystallization and testing them with scanning electron microscopy and transmission electron microscopy. This paper also discusses the mechanism of the earthen sites consolidated with PS materials，and proposes the following conservation methods：chemical consolidation method against wind and rain erosion to earthen sites with PS as the consolidating materials；consolidation method combining bamboo-steel composite anchor and crevasses grouting for dangerous soil masses；and consolidation method associating back-filling and patching-up for the eroded parts of the earthen sites. These consolidation methods provide a key to the main problem of the arid earthen sites basically；and they are practicable and applicable.

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WEATHERING CHARACTERIZATION AND CONSERVATION TREATMENT OF CLIFF AT MOGAO GROTTOES

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2009, 28 (05): -1055 doi:
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Detailed investigations conducted on the rock cliff of Mogao Grottoes show that physical weathering is the major factor responsible for the deterioration of cliff rock. From the viewpoint of reinforcement engineering，weathering hazards in Mogao Grottoes are classified into 9 kinds with 3 different intensities in relation to micro- geomorgraphy. Various treatments are evaluated and suggested for engineering design；such as the PS consolidation of cliff surface，crack grouting，cable stabilization to unstable rock mass，topping of thin-covered caves and removing of unfavorable structures for stabilization constructed in the early time. The reliability of the treatments is proven and the frame structure for design of reinforcement engineering in Mogao Grottoes is established.

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RESEARCH ON CLIFF DEFORMATION FEATURE OF JIAOHE RUINS DURING AND AFTER ANCHORING AND GROUTING

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2009, 28 (05): -1064 doi:
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Based on the largest earthen architecture conservation engineering，Jiaohe ruins rescuing conservation engineering，and the particularity of the cliffs，Nanrui dam automatic monitoring instrument is applied to survey the deformation of cliffs during anchoring and grouting. Analysis of the monitoring of the cliff proves grouting disturbs the cliffs more intensely than anchoring. The deformation characteristics of the cliffs before and after the conservation illustrate the successful conservation of anchoring and grouting. The conclusion provides the foundation for entire scientific conservation of Jiaohe ruins；furthermore，it gives the reference to the research on the anchoring and grouting of similar earthen architectures.

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SATURATION STRENGTH OF EARTHEN RUINS REINFORCED BY POTASSIUM SILICATE AND INFLUENCE OF ENVIRONMENTAL FACTORS ON REINFORCEMENT EFFECT

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2009, 28 (05): -1074 doi:
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Unconsolidated undrained(UU) shear tests were carried out on PS reinforced loess specimens from the ancient city of Jiaohe. Soil specimens were initially reinforced by different PS solutions and then were subjected to saturation before UU tests. At the same time，PS reinforced specimens were subjected to disintegration test in water，to wind erosion test in wind tunnel，to freeze-thaw test，to temperature fluctuation test，and to humidity variation test；so that the influence of serious environment of the ancient Silk Road on the reinforcement effect is studied. Specimens reinforced by 3%PS and 7%PS show higher peak shear strength by 90% and 360% respectively，as compared with unreinforced specimens. The addition of 3%PS and 7%PS reinforcement also result in higher residual shear strength by about 50% and 250% respectively. These results show that PS reinforcement is still effective when subjects to saturation due to rainfall；so that PS is suitable for conservation of the earthen ruins in arid area of the Silk Road.