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2009, 28 (04): -0 doi:
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A NUMERICAL MODEL FOR FULLY COUPLED THM PROCESSES WITH MULTIPHASE FLOW AND CODE VALIDATION

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2009, 28 (04): -649 doi:
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[PDF 563 KB] (1975)

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A numerical model for fully coupled THM processes with multiphase flow in porous media was developed based on the momentum，mass and energy conservation laws of the continuum mechanics and the averaging approach of the mixture theory over a solid-liquid-gas three-phase system. To characterize multiphase THM coupling and to make the governing equations closed，complete and compatible，six processes and their coupling effects were considered，including stress-strain，water flow，gas flow，vapor flow，heat transport and porosity evolution processes. The physical phenomena such as phase transition，gas solubility in liquid，thermo-osmosis，moisture transfer and moisture swelling were modeled. As a result，the relative humidity of pore gas was defined on a sounder physical basis，avoiding the traditional definition as a negative exponential function of suction and absolute temperature. By selecting displacements，pore water pressure，pore gas pressure，pore vapor pressure，temperature and porosity as basic unknown variables，a finite element formulation was then established，and a three-dimensional computer code，THYME3D，was developed，with each node of 8 degrees of freedom. The bentonite THM Mock-up experiments performed by CEA were employed to validate the mathematical model and the software. The main coupling mechanisms involved in the experiments were satisfactorily simulated in the validation，and the effects of the governing equations，the constitutive relations and the parameters on the coupled THM processes were understood. The work developed enabled further in-depth research on fully coupled THM or THMC processes in porous media.

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THEORETICAL ANALYSES OF FRACTURE REGULATION OF HOMOGENEOUS ROCK BAR IN CASE OF RANDOM INCIDENCE OF STRESS WAVE

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2009, 28 (04): -666 doi:
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[PDF 207 KB] (1132)

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According to the view of random arrival time of incident wave，theoretical analysis is carried out on the dynamic fracture regulation of rock bar. Through theoretical calculation of pure tensile stress caused by the superposition of incident compressed waves and reflect tension waves after triangle stress wave，rectangle stress wave and exponential attenuating stress wave propagate to the free end of one-dimensional homogeneous rock bar in several specific incidence periods. The possibility of fracture，the potential fracture time，numbers and length of rock bar are systemically analyzed. The relationship among the numbers and length of fracture and the peak value of stress wave and incident time is established；meanwhile，the inherent essence of random phenomenon in rock dynamic fragmentation is disclosed.

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INFLUENCE OF DEEP-HOLE CONTROLLED PRE-CRACKING EXPLOSION ON MICROSTRUCTURE OF COAL

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2009, 28 (04): -673 doi:
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[PDF 283 KB] (1525)

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To find out the influence of deep-hole controlled pre-cracking explosion on microstructure of coal，a field test of deep-hole controlled pre-cracking explosion was carried out in a mine located in south China. In the test，the microstructures of some coal samples，taken from different spots that were 3.0 to 9.7 m away from the explosive hole，were observed carefully with ASAP–2010(automated surface area analyzer–2010). Besides，the performance of gas drainage was studied. The results showed that，with the increment of distance from explosive hole，the Langmuir surface area and BET surface area decreased linearly. At the spot 9.7 m away from explosive hole，Langmuir surface area and BET surface area decreased 68.8% and 15.26% respectively. The volumetric ratio and area ratio of micropores decreased at first and increased then. On the contrary，the volumetric ratio and area ratio of small-pores and mid-size-pores increased at first and decreased then. The volume ratio of penetrating pores increased a little at the beginning and decreased then. The peak value，which was 26.88%，was 3.9 m away from the exploding hole. After explosion，the highest gas drainage volume increased 36%，and the total gas drainage volume in the first 15 days increased 93%. The optimum distance among exploding holes of deep-hole controlled pre-cracking explosion should be between 10 to 12 m.

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QUANTIFICATION OF ELEMENTS FOR GEOLOGICAL STRENGTH INDEX IN HOEK-BROWN CRITERION

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2009, 28 (04): -679 doi:
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The development of rock mechanical parameters estimation methods using rock mass mechanical parameters in Hoek-Brown criterion as well as measures of improvement in the process are traced to the source. However，geological strength index(GSI)，the newest method created by E. Hoek，has two deficiencies：depending on qualitative description completely and subjective experiences by individuals. By further study，it is discovered that the physical factor which determines geological strength index is the type of rock structure, and the chemical determining factor is weathering condition. Then，quantitative description of rock structure is achieved by introducing rock-mass block index based on drilled rock samples of different complete lengths. Meanwhile，absolute weathering index，which denotes rational index of weathering condition，is put forward based on the fact that rock weathering is the process of lithology changing caused by original mineral hydrolyzation and mineral alteration led by leaching out；and the calculation method is studied as well. Then，through organic combination of rock mass block index and absolute weathering index in the general sector scope table，the quantitative method of GSI is constituted. Finally，the mechanical parameters of surrounding rock in a highway tunnel are estimated，such as deformation modulus，tensile，compressive and shearing strength etc.，and the pitch of cave arch is calculated as well. Relative error is around 14% compared with measured data；so the feasibility and effectiveness of the quantitative method are confirmed.

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INFLUENCE OF FLUID ON NONLINEAR ELASTIC BEHAVIOR OF ROCK

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2009, 28 (04): -687 doi:
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The experimental results of dry and fluid-saturated sedimentary rocks，metamorphic rocks，and igneous rocks are compared using different methods and frequency bands. It is shown that in low frequencies，the attenuation and dispersion of dry rocks are much smaller than those of saturated rocks，which can be negligible. The attenuation peaks of saturated rocks vary with the viscosity of fluid. At acoustic frequencies，there are large differences in the stress-time curves between dry and saturated rocks. The hysteretic effect of fluid causes dispersion and encumbrances the unloading so that the curve falls more slowly. As the viscosity increases，the hysteretic effect increases，which demonstrates the unique properties of viscoelastic materials. The global stress-strain curves show that the strength of dry rocks is larger than that of saturated rocks. The strength of parallel stratifications is larger than that of vertical stratifications，which makes the rocks anisotropic. The anisotropy of dry rocks is very small，while it is enhanced by the fluids. At low saturation，the moduli and velocities of waves decrease as the saturation increases. However，at high saturation，the moduli and velocities increase with saturation. The moduli and velocities remain steady and unchanged at medium saturation area. These experimental results can be explained by the fact that in PM model，the microscopic nonclassical nonlinear units are easier to be activated，leading to the increase of nonlinearity and diagonal density of PM space. These mentioned phenomena caused by the effect of fluids threaten some major rock projects so that attentions should be paid.

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EXPERIMENTAL STUDY OF EFFECT OF GAS PRESSURE ON GAS SEEPAGE OF OUTBURST COAL

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2009, 28 (04): -697 doi:
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[PDF 189 KB] (1538)

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Based on the briquette specimens of the outburst coal seam #7 of typical coal and gas outburst mine of Datong a mine of Songzao Coal and Electricity Co.，Ltd.，the experiment of outburst coal¢s gas seepage was carried out under fixed axial and confining pressures but changeable gas pressure by a self-developed triaxial permeameter. The experimental results are as follows. The gas seepage velocity of outburst coal samples increase with the increase of gas pressure under fixed axial and confining pressures. And the relationship between gas seepage velocity of outburst coal samples and gas pressure can be described as power function. The increasing rates of pressure gradient of two sides of outburst coal decrease with the increase of gas pressure and reach to zero at last. The increasing rate of the gas seepage velocity of outburst coal samples was decreasing with the increase of gas pressure and reaches to a constant value at last. The experimental results are of great significance in improving the efficiency of gas extraction.

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STUDY OF INFLUENCE OF SOIL PLUG ON DRIVING PILES OF OFFSHORE OIL DRILLING PLATFORM

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2009, 28 (04): -703 doi:
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[PDF 260 KB] (2333)

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Based on the Terzaghi¢s bearing capacity theory for deep foundations，a new approach for soil plug assessment is put forward，in which the surcharge effect and the influence of driving piles on surrounding soil have been considered；and the dynamic effect coefficients are included. The approach has been applied to practical engineering projects；and the calculated results agree with the observed data very well，indicating that the approach can give more reasonable results than the currently used method.

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EXPERIMENTAL STUDY OF INFLUENCE OF CAST BLASTING ON
INNER DUMP SLOPE STABILITY

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2009, 28 (04): -710 doi:
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[PDF 367 KB] (1227)

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The high-step slope stability of inner dump slope in Heidaigou opencast coal mine under the influences of cast blasting is studied by dynamic similarity simulation experiment and digital speckle correlation method. The results indicate that a lot of rocks above seam are broken and cast to inner dump during the course of cast blasting. The blasted settlement is 17 cm；and the size of blasted rock fragment is homogeneous. The stress wave is strongly directional；and the relative motion occurs at contact plane between inner dump slope and seam earth. The horizontal displacement to free face and settlement occur in the slope；and the settlement in inner slope is the largest. The movements of the inner dump slope，relative to bench height，are very small，which would not lead to landslide or damage. Therefore，it is feasible to apply dynamic similarity simulation experiment to study slope deformation.

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SIMULATION OF COMPRESSIVE FAILURE PROCESS OF COLUMNAR JOINTED ROCK MASS AND ITS FAILURE MECHANISM ANALYSIS

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2009, 28 (04): -716 doi:
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[PDF 699 KB] (1523)

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The columnar jointed rock mass is considered as a macroscopic composite material in a broader sense. A softening model of mixed multi-weakness planes is developed. Based on the second developing platform of constitutive model in FLAC3D，the mixed softening model has been successfully established and embedded. Taking the geological conditions of Baihetan Hydropower Station as research background，uniaxial and triaxial compressions of columnar jointed rock mass are simulated；and then the failure processes of test blocks with different dip angles and directions are analyzed. The distribution of fractured planes and the failure modes are achieved；and the failure law of general significance is summarized. Through triaxial compression test，it is obtained that the strength of columnar jointed rock mass and cohesion of joint surface can reach high level under certain in-situ stress level，which agrees well with the results of field investigation. Meanwhile，the laws of load and deformation，occurrence of failure zone，distribution and development of fractured zone as well as energy dissipation are studied. Failure mechanism in many respects is discussed so as to better understand the mechanical properties.

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STUDY ON 3D PHYSICAL MODEL TEST OF SEEPAGE
OF DEEP-BURIED LONG AND LARGE DIVERSION TUNNEL

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2009, 28 (04): -725 doi:
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[PDF 484 KB] (1344)

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Geomechanical physical model test is one of the main methods to solve underground engineering problems. Based on the diversion tunnel project of Jinping II Hydropower Station，physical simulation of the construction process of deep-buried long and large diversion tunnel under high seepage pressure is conducted. The hydraulic serve-controlled water supply system and discrete holey tube seepage generation system are designed and made to realize the high simulation of seepage field. Calculation analyses of the seepage and evolution law inside the surrounding rocks of diversion tunnels during dynamic construction process are conducted. The scientific rationality of the model seepage test system is proved by the comparison of the calculated and measured results of osmotic pressure of characteristic points inside the solid model. According to experimental results，the theoretical basis for the anti-seepage construction technology design of diversion tunnels is provided；and it is of great significance for the long-term stability，safety evaluation and prediction of diversion tunnels.

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VARIABLE PARAMETERS-BASED CREEP DAMAGE CONSTITUTIVE MODEL AND ITS ENGINEERING APPLICATION

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2009, 28 (04): -732 doi:
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[PDF 407 KB] (1444)

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Considering effects of weakness of rock parameters，a creep damage constitutive model with variable parameters is proposed. In the model，the creep parameters of the rock are weakened with time gradually，so the deterioration process of the material can be reflected by unsteady creep parameters directly. The central difference equation in three-dimensional condition of creep damage constitutive model is deduced. The constitutive model is programmed by the secondary development of software FLAC3D using C++ and FISH. The model is applied in slope project of dam foundation at Dagangshan Hydropower Station. Based on the results of the compressive creep test，the creep damage parameters of rock mass in dam site are inversed. Reasonable evaluation and suggestions for the slope design and construction are provided though three-dimensional calculation of creep damage stability of the slope excavation at Dagangshan Hydropower Station.

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MICROSEISM SOURCE LOCATION WITH HIERARCHICAL STRATEGY BASED ON PARTICLE SWARM OPTIMIZATION

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2009, 28 (04): -740 doi:
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[PDF 334 KB] (1827)

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According to the fact that it is difficult for typical microseism location(TMSL) algorithm to select a proper velocity structure and that it is not easy for joint microseism location(JMSL) algorithm that velocity structure，microseismic source coordinates and time of microseismic occurrence are associated with each other to identify unique solution，the intelligence microseism source location algorithm with hierarchical strategy(IMSHL) is suggested. Firstly，effective microseism signals are acquired by removing background noise，dividing P-wave，S-wave，correcting monitored arrival time，deleting poor microseism signals and so on；secondly，velocity structure and microseismic source coordinates are identified using particle swarm optimization(PSO) based on minimizing residual sum of squares of calculated and monitored difference of arrival time between two neighboring sensors；thirdly，analytic solution of microseism occurrence time can be gained by minimizing residual sum of squares of calculated and monitored arrival time based on the identified velocity structure and microseismic source；finally，the correction of selecting microseism signals and the accuracy of microseism source location are verified by back analysis based on the in-situ state of practical exploitation，and if necessary，source location and identification of microseism signals should be carried out for the second time. A simple example shows that convergence precision of the algorithm is improved compared with TMSL，and convergence velocity and the stability of the algorithm are also improved compared with JMSL. The correlation of coordinates of certain seismic sources and velocity for IMSHL is shown by correlation analysis，and its necessary condition and locations of several special seismic source are also provided. The analysis of the performance of IMSHL shows that，in order to further improve convergence velocity，precision and stability of solution，microseismic source should be in ranges of sensor array and close to the sensors as much as possible by proper disposal of the sensors；and the sensors should not be in the location that makes coordinates of seismic sources and velocity associated with each other. Lastly，the feasibility and advantages of IMSHL are verified by an in-situ blasting test and the applicability of several velocity structures is discussed and analyzed.

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FISHER DISCRIMINANT ANALYSIS MODEL AND ITS APPLICATION TO PREDICTING DESTRUCTIVE EFFECT OF MASONRY STRUCTURE UNDER BLASTING VIBRATION OF OPEN-PIT MINE

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2009, 28 (04): -750 doi:
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[PDF 232 KB] (1828)

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Based on the Fisher discriminant theory and the actual characteristics of the project，a Fisher discriminant analysis(FDA) model to predict the destructive effect of masonry structure under blasting vibration of open-pit mine is established. Eight major factors are taken into account from the aspects of blasting vibration and structure dynamic characteristics such as peak particle velocity(PPV)，dominant frequency，dominant frequency duration，mortar joints intensity，collar beam structure，height of housing，roof forms and the rate of brick walls. After training and testing 108 sets of measured data in a open-pit mine，the discriminant functions of FDA are solved，and the ratio of mistake-distinguish is 0.083. The functions show that PPV is the most important discrimination indicator，followed by the structural columns of collar beam，roof forms，the rate of brick walls，housing height，the main frequency，the main frequency of duration and intensity of mortar joints，which provides efficient and accurate reference to forecast the destructive effect of masonry structure from blasting vibration. Another 12 groups of measured data are tested as forecast samples，and the predicted results are consistent with the measured ones. The prediction accuracy of FDA model is acceptable，so it is a new approach to predict destructive effect of masonry structure under blasting vibration，which can be applied to practical engineering.

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EXPERIMENTAL STUDY ON ACOUSTIC EMISSION CHARACTERISTICS DURING DEFORMATION AND FAILURE PROCESSES OF COAL SAMPLES UNDER DIFFERENT STRESS PATHS

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2009, 28 (04): -757 doi:
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[PDF 380 KB] (1348)

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Based on investigation of acoustic emission(AE) characteristics during deformation and failure process of coal specimens under different stress paths，the general uniaxial compression，triaxial compression and confining pressure reduction experiments were performed by RMT–150B rock mechanics test system，in which coal specimens were from Gengcun Mine，Yima Mining Group with outburst proneness. Test results indicate that the AE characteristics of coal specimens were different in deformation and failure process under different stress paths. In experiments of general uniaxial compression，AE events of different degrees took place on every stage. Compared with experiments of uniaxial compression in triaxial cylinder，the values of AE counts and energy were obviously larger and the momentary values of maximum AE counts and energy at failure were approximately equal. In experiments of general triaxial compression，AE events were fewer before yielding and increased obviously then. At stage of post-yielding，AE events were quite active and enhanced rapidly，which was a sign of failure portent，and the value of AE counts and energy reached maximum at failure instantly. In experiments of confining pressure reduction，AE events were fewer，because the specimens were in elastic stage before confining pressure was relieved. With decreasing confining pressure and friction provided by positive stress，the inner zones of samples with low strength yielded to fail gradually and formed microcracks. AE events occurred in small amount in previous yielding stage，while AE counts and energy were quite active and enhanced rapidly in late yielding stage，which was also a sign of failure portent，and AE counts and energy reached maximum value and failed instantly. Compared with general triaxial compression，the maximum values of AE counts and energy were much larger；and the results indicate that the failure of coal samples in experiments of confining pressure reduction were more violent. In experiments of uniaxial compression in triaxial cylinder，general triaxial compression and confining pressure reduction，AE totalized counts and energy were approximately identical.

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TWO-STAGE ANALYSIS OF INITIAL GEOSTRESS FIELD AT DAM SITE ZONE OF HIGH ARCH DAM

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2009, 28 (04): -767 doi:
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The large-scale finite element model for dam site zone of Xiaowan Hydropower Station is established，in which the influences of topography and river turning are taken into consideration. The method combining genetic algorithm with finite element method is applied to the first-stage back analysis of initial geostress field at dam site zone. Then，the small-scale finite element model of dam foundation excavation and relaxation is established，considering the main soft geological structures in the vicinity of the dam site. Based on the sub-model method，the displacement boundary conditions of the small-scale model can be achieved by interpolating from the large-scale model of the first-stage back analysis，and calculation for the second-stage analysis of geostress field is conducted. Through comparative analysis，it is shown that the main soft geological structures have much effect on the results of initial geostress field，especially in the vicinity of discontinuity during the first-stage back analysis. And the precision of the initial geostress field in the first-stage back analysis has been greatly improved in the second-stage calculation. The geostress of most measuring points are much closer to measured values and the relative error has also been reduced gradually. So the initial geostress field after two-stage analysis can be used in the later analysis of relaxation effect during dam foundation excavation. And the results also indicate that the method is feasible and of great reference to similar projects.

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GEOLOGICAL EVOLUTION ANALYSIS AND NUMERICAL SIMULATION
OF QUJIAWAN LANDSLIDE GROUP IN DONGPING RESERVOIR

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2009, 28 (04): -775 doi:
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Based on the analyses of regional geological structure and the geological structure of Qujiawan landslide group in Dongping reservoir area，taking stratigraphical occurrence，hydrometeorological factors into account，it was hard to form large-scale rock landslides during the evolution processes. But speculating with the incised direction of the river valley，large-scale collapse of bedrock of the right bank may be induced by 3 times of tectonic movement which forms the three terraces of left bank of Zhongjian River because of intense structural role. According to the characteristics of collapse deposits and the river width，it is possible that large-scale collapse deposits are moved to the left bank of the river，covering upon the terraces，which is supported by photos from field investigation and analysis of mechanical parameters from bedrock. Five important stages during the evolution processes are selected and analyzed combining engineering geology and geological methods，considering that the landslides are on the axial part of Zhongjian River anticline，the characteristics of river valley incising along weak tectonic rock zone in geomorphology and the trail results of the parameters of geotechnical experiment，in order to determine section shape of the slope in each stage and draw geologic profile. Then geomechanical model is established by using FLAC3D；and a dynamic numerical simulation for the 5 important stages is carried out. From the calculation result，the speculation that collapse deposits from the right bank can pack on the left bank has been confirmed. Meanwhile，it is well explained that the deposits on left bank are much thicker than that on right bank；and there is an obvious difference in surface elevation between the two banks.

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CALCULATION METHOD OF EQUIVALENT ACCELERATION FOR LIMIT EQUILIBRIUM ANALYSIS OF SLOPE UNDER BLASTING VIBRATION

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2009, 28 (04): -784 doi:
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[PDF 218 KB] (1260)

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Based on wave theory，the displacement，the blasting vibration acceleration，and the stress state of slope under the same blasting vibration velocity but different vibration frequencies were studied. The results indicated that with the same blasting vibration velocity，the peak vibration displacement was in inverse proportion to the vibration frequency，while the blasting vibration acceleration was proportional to the vibration frequency；however，the maximum stress of the slope was unchanged. There was no direct relation between acceleration and stress state of the slope，and the higher the vibration frequency was，the more quickly the displacement，the acceleration and the peak stress varied along the depth of the slope. According to comprehensive consideration of mutual relationship between vibration frequency，vibration acceleration and stress state of the slope，the method of converting the acceleration in higher frequency to acceleration in lower frequency of blasting vibration was obtained. Based on the fact that the same peak stress in the slope was created by the same peak particle vibration velocity，the equivalent acceleration calculated method for limit equilibrium analysis of slope under blasting vibration was proposed，which provided theoretical basis of analyzing the slope stability under blasting vibration during slope construction.

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EXPERIMENTAL STUDY OF LAWS OF GAS SEEPAGE IN LOOSE FRAGMENTED MEDIUM

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2009, 28 (04): -791 doi:
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For in place leaching of fragmented uranium ore by blasting，the ore heap is a loose fragmented medium，whose particle sizes follow the Rosin-Rammler distribution. The gas seepage in the medium is influenced by characteristic particle size，particle size distribution index and porosity simultaneously. To study the influence，seven samples are compound with different particle size gradations based on Rosin-Rammler distribution. The laws of gas seepage in seven samples are studied based on self-developed apparatus. On the basis of the test results，the adaptive neuro-fuzzy inference system(ANFIS) model for predicting seepage ratio and inertial coefficient is established using the adaptive neuro-fuzzy inference system based on characteristic particle size，particle size distribution index and porosity. The research results show that gas seepage in fragmented medium does not follow Darcy¢s law but follows Darcy-Forchheimer¢s law. Therefore，the ANFIS model provides predictions with high accuracy，which proves to be a new approach for estimation of permeability and inertial coefficient.

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2D DISPLACEMENT FIELD MEASUREMENT FOR MODEL EXPERIMENT BY SINGLE-VIEW METROLOGY WITH RANGE CONTROLS

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2009, 28 (04): -799 doi:
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A single-view vision metrology with range controls is used in displacement measurement of highway landslide and cutting slope model experiment instead of commonly used physical or mechanical methods. It applies non-metric digital camera as the main tool，and only needs some distances of data points instead of coordinate controls on model plane. The homography between model plane and image plane can be recovered by the constrained least-square adjustment，which avoids the dependence on particular geodetic instruments such as theodolites or electronic total stations. The camera is placed perpendicularly to the object plane，and interior and exterior parameters are fixed during experimental period to capture one ortho-image of the model plane at each epoch. Then，the displacement field can be acquired through the post processing of the captured image sequences by the procedures of target accurate measurement，homography matrix calibration，the lens distortions and rigid body transformation displacement elimination. The results indicate that the approach is more convenient and with higher precision，which can be used in engineering applications with accuracy requirement less than 1 mm.

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INTERVAL NON-PROBABILISTIC RELIABILITY COMPREHENSIVE ANALYSIS METHOD FOR STRIP FOUNDATION STABILITY BASED ON BEARING CAPACITY AND SETTLEMENT

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2009, 28 (04): -805 doi:
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[PDF 272 KB] (1049)

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The interval values are used to denote the soil mechanical parameters，which can reflect the uncertainty of parameters values. The determining methods are also proposed according to the characteristics of parameters. The interval non-probabilistic reliability analysis model of strip foundation bearing capacity is developed based on study of calculation method of foundation bearing capacity. And the interval non-probabilistic reliability analysis model of strip foundation settlement is also established based on the settlement calculation method. Then，the solution of non-probabilistic reliability indexes is performed by interval theory and one-dimensional optimization algorithm. The comprehensive evaluation is carried out through the established reliability evaluation rules. The interval non-probabilistic reliability comprehensive analysis method for strip foundation stability based on bearing capacity and settlement is finally presented，which can reflect the influence of bearing capacity and settlement on strip foundation stability comprehensively. The calculation of engineering examples proves the feasibility of the method，which perfects the method and theory of reliability analysis for strip foundation.

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INVERSION OF MONITORED DISPLACEMENT FIELD AND EVALUATION OF SURROUNDING ROCK STABILITY OF UNDERGROUND CAVERNS

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2009, 28 (04): -813 doi:
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[PDF 230 KB] (1351)

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As monitoring instruments only reflect the deformation characteristics of local surrounding rock during the excavation process of underground complexes，an assessment method based on the spatial field of underground complex¢s global deformation is presented. By employing the concept of physical field，the monitoring data can be standardized. Then，the data inversion can be conducted in three-dimensional spaces. According to the inversion results，the warning line method is employed to evaluate the global stability of surrounding rock. The proposed method has been successfully applied to the analysis of surrounding rock stability in a number of large-scale underground complexes，such as Pubugou and Xiluodu projects. These engineering applications indicate that the proposed method can timely reflect the current deformation of underground complex. And comparing with other numerical methods，it is also accurate and effective，which offers a quicker and more direct solution.

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MEASURING METHOD OF GEOMATERIAL THERMAL CONDUCTIVITY BASED ON DISTRIBUTED OPTICAL FIBER SENSING TECHNOLOGY

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2009, 28 (04): -819 doi:
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[PDF 301 KB] (1593)

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Based on theory of linear heat-source，the basic principle of distributed fiber optical technology for thermal conductivity measurement is described. The measurement process，method and apparatus are introduced. Test model is also built；and the thermal conductivities of three types of geomaterials with different water contents are measured by using distributed fiber optical technology. By means of analyzing test data，the relationship between fiber optical temperature and time is studied. Temperature curve is made up of two segments，i. e. swift growth and gradual uniform growth segments. At uniform growth segment，there is a well logarithm relationship between temperature and time，which approves the feasibility of this method. Through analyzing the effect of heating power on thermal conductivity，the effect of heating power on thermal conductivity can be ignored when the heating power is in the range of this test. Through research of water content¢s effect on thermal conductivity，it is found that water content has dramatic effect on thermal conductivity. Thermal conductivity increases with the increment of water content，but the increasing rates of different media are different. At last，this method is discussed.

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UNIFIED ANALYTICAL SOLUTIONS FOR CYLINDRICAL CAVITY EXPANSION IN SATURATED SOIL UNDER LARGE DEFORMATION AND UNDRAINED CONDITIONS

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2009, 28 (04): -827 doi:
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[PDF 254 KB] (1162)

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The strain distribution around the cylindrical cavity is classified into plastic zone and elastic zone. The theories of small deformation and large deformation are adopted in the elastic zone and plastic zone respectively. According to the stress equilibrium equation and conditions of stress and strain，the stress distribution in two zones，radius of the plastic，limited cavity expansion pressure and excess pore pressure are obtained considering large deformation and undrained conditions. The results agree well with those of the in-situ test，which proves that the proposed theory has certain reference value. The calculations show that with the increase of parameter b，the limited cavity expansion pressure increases nonlinearly while the excess pore water pressure is on the contrary.

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DEVELOPMENT AND APPLICATION OF AUTO HYDROGEOLOGICAL PARAMETERS MONITORING AND DATA PROCESSING SYSTEM

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2009, 28 (04): -834 doi:
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[PDF 391 KB] (1280)

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The auto hydrogeological parameters monitoring and data processing system is developed to improve efficiency of hydrogeological tests，and the slug test is introduced instead of conventional hydrogeological test. It dramatically shortens the test period and decreases the working intensity under in-situ conditions with relatively low costs because pumping and observation wells are not required. The post processing system is developed，which deals with the data of steady flow pumping test，unsteady flow pumping test and slug test at the same time，and the test reports are offered timely. Through comparative application under in-situ conditions，it is proved that the system can satisfy engineering demand，which is a good substitute for conventional hydrogeological test.

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EARTHQUAKE DAMAGE PHENOMENA AND DEFORMATION MONITORING ANALYSIS FOR CONCRETE FACED ROCKFILL DAM AT ZIPINGPU PROJECT DURING WENCHUAN EARTHQUAKE

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2009, 28 (04): -840 doi:
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Earthquake occurred on May 12，2008 in Wenchuan，Sichuan Province，with magnitude of 8.0 and epicenter intensity of XI，causing serious damage to the structures on ground. The dam height of Zipingpu concrete faced rockfill dam(CFRD) is 156 m and it is 17 km from Wenchuan earthquake epicenter，which is the largest high dam reservoir project and the nearest from earthquake epicenter in the earthquake area. Deformations and damages occurred due to the earthquake，attracting attentions from both academic and engineering fields. Detailed description and analysis are presented for damage due to deformations of dam embankment and concrete slabs based on macroscopic deformation phenomena after earthquake and deformation monitoring data. The comprehensive analysis results indicate that dam deformations are mainly settlement，and horizontal displacement is relatively small. Dam body is in the conditions of contraction and compaction. The maximum settlement occurs at dam crest，valuing 900–1 000 mm；and the ratio of the settlement to dam height is around 0.6%. No evident damages occurs in dam body and downstream slope；and structural function of dam is not seriously affected by the earthquake.

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DEVELOPMENTAL FEATURES AND EVALUATION OF BLOCKING DANGERS OF DASHUI DITCH DEBRIS FLOW IN TANGJIASHAN DAMMED LAKE

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2009, 28 (04): -850 doi:
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[PDF 752 KB] (1618)

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Dashui Ditch is located in the upstream side of Tangjiashan Mountain. It was a gully before the May 12 earthquake，however，extremely rich loose sources were formed with all conditions of the occurrence of a debris flow due to the collapses and landslides after the earthquake. It became one of the serious potential dangers of geological disasters after successful discharge of Tangjiashan dammed lake，which controlled the normal operation of Tangjiashan dammed lake as well. Through in-situ investigation，the developmental and dynamic features of Dashui Ditch debris flow was analyzed systematically combining with the developmental situation of debris flow on June 14 on the basis of identifying the distribution and stability of the groove loose sources. In particular，the possible sizes of the debris flow under different rain frequencies were studied，and the possible blocking size，duration and outburst forms were evaluated. The results were confirmed by the once in 100-year debris flow on September 24，2008.

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DISCUSSION ON“TWO-DIMENSIONAL MODEL OF HIGH SPEED UNSTABLE LANDSLIDES”

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2009, 28 (04): -859 doi:
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REPLY TO“DISCUSSION ON‘TWO-DIMENSIONAL MODEL OF HIGH SPEED UNSTABLE LANDSLIDES’ ”

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2009, 28 (04): -862 doi:
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[PDF 165 KB] (1020)