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2004, 23 (18): 3037-3037 doi:

[PDF] 133 KB (665)

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NEW RESEARCH ON FAILURE CRITERION FOR GEOMATERIAL

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2004, 23 (18): 3037-3037 doi:

[PDF] 433 KB (954)

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Two new concepts about the principal shear stress couples and their actions are proposed through the analysis of Mohr-Coulomb criterion and the twin shear criterion. Based on these concepts，a new failure criterion is given out for geomaterial. The effect of the whole three principal shear stress couples acting on the dodecahedral element should be taken into account in the establishment of failure criterion. Theoretical analyses about the loci on the p plane，the Mohr circles on the s-t plane，the effect curves of the medial principal stress and the directions of the failure surface show that the proposed criterion can basically reflect the true failure and strength characteristics of geomaterial with the verification of experimental facts.

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REASONABLE METHOD TO ESTIMATE CREEP COMPLIANCE
OF ROCKS JOINTED BY PARALLEL CRACKS

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2004, 23 (18): 3044-3044 doi:

[PDF] 291 KB (765)

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Based on Taylor model and viscoelastic fracture mechanics，a method is proposed to estimate the uniaxial，shear and voluminal creep compliance of rocks jointed by parallel cracks. First，the interaction of parallel cracks is neglected and the anisotropic creep compliance of Taylor media is computed. Then each single crack is placed in Taylor media to account for the influence of other cracks on its creep behavior. Based on the above analysis，the creep compliance of rocks jointed by parallel cracks is derived. The effect of interaction among cracks is taken into account and the creep anisotropy of cracked rocks is analyzed. According to the analysis results，uniaxial and shear creep compliance of cracked rocks increases with increment of crack density parameter and decreases with increment of crack dip. The creep compliance with account of interaction among cracks is obviously bigger than that without of interaction among cracks. The proposed method makes it possible to estimate creep compliance of cracked rocks only by experimental study on rock samples in laboratory.

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TESTING STUDY ON COMPRESSIVE MODULUS OF
LOOSE ROCK BLOCKS UNDER CONFINING CONSTRAINT

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2004, 23 (18): 3049-3049 doi:

[PDF] 236 KB (1150)

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The compressive modulus，which characterizes the deformation behaviors of loose rock blocks under confining constraint，is related with many factors，such as the pore ratio，rock strength and so on. Among them，the pore ratio is one of the most important factors. Through testing，the relationship between compressive modulus and pore ratio is revealed. The testing results show that the compressive modulus increases fast with the decrement of pore ratio. By regression analysis，the relationship between them can be described by either exponent or power function，both with very high correlation coefficient more than 0.9. The testing results indicate that the compressive modulus is approximately linearly related with rock strength within a certain rang of rock strength of 15～45 MPa and increases with rock strength. The further regression analysis suggests that both the slopes and the intercept of the regressive linear function are closely related to pore ratio. The regressive slope increment increases with the decrement of pore ratio and their relationship can be described by either the exponent function or the power function，both with very high correlation coefficient more than 0.9. The relationship between intercept and pore ratio can be described by the polynomial function with a correlation coefficient more than 0.9. At last，the relationship among compressive modulus，rock strength and pore ratio can be written as a uniform function. By comparing the two functions containing the parameter of pore ratio，obtained by two different ways with and without considering rock strength，a certain unification is found between the two functions.

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DETERMINATION METHOD OF STRENGTH PARAMETERS FOR
SANDSTONE AND MARBLE WITH ONE SPECIMEN

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2004, 23 (18): 3055-3055 doi:

[PDF] 186 KB (1111)

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It is one of the main tasks of laboratory test to determine the strength parameters. However there are some difficulties to calculate the cohesion and internal friction angle. The specimens are less，or their divergence is so great that the strength of specimen in higher confining pressure is lower. Based on the servo-control testing machine，a method is suggested in this paper to determine the Coulomb curves of sandstone and marble with only one specimen. Marble specimen has a clear yield platform when it is compressed in high confining pressure. A series of strengths can be obtained by stepping up the confining pressure in the yield platform，which is regressed for the Coulomb curves. A sandstone specimen is broken under uniaxial pressure with higher confining pressure，and then the confining pressure is reduced to keep axial deformation constant. The axial bearing capacity of the broken specimen decreases with reduction of the confining pressure，and the linear relation of them is nearly the same with the relation of the peak strength and confining pressure.

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INFLUENCE FACTORS ON STABILITY OF SURROUNDING ROCKS OF GOB-SIDE ENTRY RETAINING IN TOP-COAL CAVING MINING FACE

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2004, 23 (18): 3059-3059 doi:

[PDF] 320 KB (1016)

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Based on engineering practice，corresponding numerical models are set up by numerical analysis software UDEC for analyzing the rupture and collapse of rock strata. The displacement regularity of surrounding rocks of gob-side entry retaining in fully-mechanized top-coal caving mining face is analyzed in detail. The influences of the location of main roof rupture，length of uncaved top-coal at the end of working face，original road support，width of filling belt，filling way and strength of filling belt on the stability of surrounding rocks of gob-side entry retaining in fully-mechanized top-coal caving mining face are systematically analyzed. The results show that in prerequisite for the stability of roof and top coal，the displacement regularity of surrounding rocks should be rationally used to determine the reasonable filling pattern and filling strength，so that the filling stability can be guaranteed and a good result of retaining roadway can be also obtained.

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MECHANICAL ANALYSIS OF RUPTURE REGULARITY OF HARD AND MASSIVE OVERLYING STRATA OF LONGWALL FACE

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2004, 23 (18): 3066-3066 doi:

[PDF] 165 KB (1030)

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Based on the mechanical model of fixed beam with gravity in account，the rupture reqularity of hard and massive roof of longwall face is analyzed. In this paper，the structure of the main roof before its initial rupture is considered as the fixed beam，and the gravity of hard roof is considered as the centralizing force. By using elastic theory and analyzing the stress field of fixed beam under gravity，the mechanics judgement model of the overlying strata in three kinds of possible movement is suggested，which are that (1) the shearing with and without the weak interbedding to directly cause the key falling of strata，(2) rupture resulting from pressure and shearing in the whole strata，and (3) rupture of the strata close to two ends of beam. The suggested mechanics judgement model has been tested by field experiments，and it is useful for the prediction of the initial rupture and span of the main roof of the hard and massive strata.

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NUMERICAL SIMULATION BY DISTINCT ELEMENT CODE ON
DRAWING LAW AND INTERVAL OF FULLY-MECHANIZED COAL MINING WITH CAVING METHOD

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2004, 23 (18): 3070-3070 doi:

[PDF] 923 KB (1037)

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Feasible drawing interval is the basis to study mining equipment of fully-mechanize coal mining with caving method. It is also a key to increase recoverable ratio of coal face and to improve quality of coal. By redeveloping the distinct element software of loose grain media，the contact relation among elements is simulated by elastic and damping elements to keep consistence with top coal drawing process. Based on Windows environment，the virtual wall is made to simulate distinctive multi-layer media. Under the condition of 0.8 m width of falling opening with lower position falling method，the falling law of top coal is simulated by distinct element method in different drawing intervals of 0.6，0.8，1.0，and 1.2 m. In the light of loss ratio of top coal and refuse rate，the drawing law and the feasible interval are studied and it is found that the scientific drawing interval is 1.0 m and the lower limit is 0.8 m. The study results of this paper are applied to determine the cut depth of coal-winning machine and the moving interval of support and conveying equipment. By using this equipment with interval of 0.8 m，the mining technology of one cut by one drawing and parallel operation is successfully applied to raise the standard of high production and effect.

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3D NONLINEAR SEEPAGE ANALYSIS FOR ROCK-SOILS
WITH FINITE ELEMENT METHOD

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2004, 23 (18): 3076-3076 doi:

[PDF] 248 KB (1002)

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From the point of seepage mechanism，3D nonlinear seepage analysis is made for the case in which Darcy law is not available. The controlling factor and formula representation of nonlinear seepage are discussed. 3D nonlinear seepage analysis is carried out on rock-soils with FEM，based on an empirical nonlinear relation between seepage velocity and hydraulic gradient. The nonlinear seepage controlling equations are derived by using Galerkin FEM，and numerically solved by direct iteration. Some issues，including the criteria of iteration convergence，improvement of the calculation precision，and acceleration of convergence，are discussed. An explanatory example is given，and the numerical result is very close to theoretical solution. The study result shows that the presented approach is of simplicity for programming，high computational efficiency and fast convergence.

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3D SIMULATION AND ANALYSIS ON CONSTRUCTION BEHAVIOR OF
FORKED METRO TUNNEL

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2004, 23 (18): 3081-3081 doi:

[PDF] 466 KB (1104)

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Forked line 2# of Da—Ke running tunnel of Shenzhen metro is a complicated multi-tunneling system，with bad geological condition and strict envirionment restriction around it. In this paper，the optimized analysis on construction is done and complex 3D FEM model is set up. The ground subsidence and stability of surrounding rocks during construction are analyzed with 3D elasto-plastic FEM. From FEM computation，the maximum ground subsidence is less than 30 mm during excavation，and the failure zones of surrounding rocks and internal forces and deformation of tunnel support are also analyzed in detail. The analysis results have been proved by the real engineering that has been very successfully built.

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ADAPTIVE NEURO-FUZZY INFERENCE APPROACH FOR
BACK ANALYSIS OF DISPLACEMENTS

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2004, 23 (18): 3087-3087 doi:

[PDF] 205 KB (902)

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Current approaches for back analysis of displacements have some shortcomings. For optimization theory-based approach，it is easy to get trapped at local optimalization，instable in identifying optimal solution，and slow in converging for many parameters to be inversed. For artificial neural network based-approach，it is difficult to converge with desired accuracy when the search space is relatively large，and，furthermore，to get the sole inversion results because of the indefiniteness of trained network. The genetic algorithm-based approach can get the optimal solution only if experience-based interference is implemented. The approach based on artificial neural networks and genetic algorithms is effective only if the search space is relatively small. As a result，new approach for back analysis of displacements has to be established to overcome the shortcomings. Adaptive neuro-fuzzy inference system is used to establish the new approach for back analysis of displacements. The approach has been used to inverse the mechanical parameters of a prescribed elasto-plastic problem. The inversed results show that this approach can rapidly get a stable and accurate solution within a relatively large solution space and the approach is superior to current approaches.

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APPLICATION OF GIS-BASED NEURAL NETWORK WITH FUZZY
SELF-ORGANIZATION TO ASSESSMENT OF ROCKBURST TENDENCY

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2004, 23 (18): 3093-3093 doi:

[PDF] 223 KB (904)

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Rockburst tendency is one of the important indices for the safety evaluation of deep mining engineering. The accuracy of rockburst tendency analysis and assessment is utterly dependent on the reliability of raw mechanics data and the rationality of mathematical models. To upgrade the reliability of data，geographical information system (GIS) is used to support management of multi-resource raw data，perform data processing，refine map layer for the factors needed in analysis，and easily divide the region into units for analysis. Then，via secondary programming based on GIS，the neutral network model with fuzzy self-organization is combined with GIS and conventional methods tightly for rockburst tendency assessment，i.e.，GIS takes the role of providing input data for the neutral network with fuzzy self-organization as well as processing its analysis results and outputting them in forms of maps. The feasibility and practical methods to integrate neutral network with fuzzy self-organization and GIS are discussed in this paper，in the light of a deep mine in China.

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PROBABILITY MODEL FOR ROCKBURST PREDICTION

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2004, 23 (18): 3098-3098 doi:

[PDF] 181 KB (931)

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Based on the failure phenomena and the distribution feature of strength probability from the uniaxial compressive strength test of rock，a new point of view is introduced that rockburst intensity reflects the probability of rock failure. The relation is established between rockburst intensity and probability distribution of uniaxial compressive strength of rock，and the formulas about the probability of different rockburst intensities under different stresses are obtained. This prediction model of rockburst intensity reflects the principal regularity of rockburst in tunnel and it can be applied to predict the probability of rockburst intensity of all levels under different stresses. A practical example shows that this prediction model is available.

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FAULT ROCKBURST I IS SNAP-BACK DUE TO SHEAR STRAIN LOCALIZATION

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2004, 23 (18): 3102-3102 doi:

[PDF] 231 KB (992)

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Four kinds of equivalent criteria of snap-back for the one-dimensional fault rockburst model under shear loading are proposed based on gradient-dependent plasticity. The relationship among rockburst，shear strain localization and snap-back (class II behavior) are discussed in detail. It is found that shear strain localization initiated at peak shear stress is a precursor of a rockburst and it is the reason for appearance of class II behavior. According to the minimum potential energy principle and the gradient-dependent plasticity，the instability criterion of the system composed of shear band and elastic rock mass outside the band can be derived theoretically. By using the displacement method，the total shear displacement can be divided into elastic part and plastic part，and the pastic shear displacement is dependent on the thickness of shear band. As a result，the condition of class II behavior of the system can be proposed. It is found from the study result that the condition of class II behavior is identical with the instability criterion of the system. If the plastic shear displacement along the tangential direction of fault band or average plastic shear strain increases faster than the elastic shear displacement or average elastic shear strain decreases，then the system shows class I behavior，otherwise it shows class II behavior. The instability criterion shows that the larger the ratio of elastic zone size to the thickness of the shear band is or the lower the ratio of the shearing elastic modulus to the shear softening modulus is，the more unstable the system is.

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EXPERIMENTAL STUDY ON SPLIT TEST WITH FLATTENED DISK
AND TENSILE STRENGTH OF ROCK

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2004, 23 (18): 3106-3106 doi:

[PDF] 405 KB (1998)

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The tensile strength can be determined from the split test of a disk specimen，or Brazil test. However the rock near loading points will yield and fracture，which is different from its testing principle. Two flats compressed in uniform deformation are introduced to the Brazilian disk to improve the stress state. From the results of FEM，the tensile stress in the center of disk decreases with the central angle of the flats，and the ratio of compressive stress to tensile stress increases as well. So it must be studied whether the Griffith criterion in tensile region is true or not true，and how to choose the central angle of flattened disk. The flattened disks of granite，sandstone，lime and diabase with central angle of 20°～90° are tested. The disks do not crack along their symmetric lines，and the tensile strength increases with the central angle of flats，which results from that Griffith criterion gives a higher tensile strength and there is friction effect between flats and the ends of testing machine. The disks crack symmetrically when plastic cushions with thickness of 0.5 mm are used. But the plastic cushions produce new friction in opposite direction，which causes that the strength of disk decreases with increment of central angle. The tensile strengths of circle disk and flattened disk are well matched for granite. The Brazil strength is 13 MPa，and the uniaxial compressive strength is up to 240 MPa. Except the granite，Brazil strengths of the other rocks are much lower than that of the flattened disks，which results from the localized load in Brazil test. In order to reduce the effect of friction and the flat quality of specimen on test results，the better choice of central angle of the flat is 20°～30°。

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NUMERICAL SIMULATION OF THE EXPERIMENT ON ROCK WITH PREEXISTED CRACKS UNDER COMPRESSION AND SHEARING

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2004, 23 (18): 3113-3113 doi:

[PDF] 599 KB (1264)

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A numerical simulation of the experiment on rock with preexisted cracks under compression is presented by using a rock failure process analysis code，RFPA2D. It is shown that most of the wing cracks initiate from the tips of preexisted cracks and eventually align themselves with the load direction. This result is of good agreement with the previous experiment. Though some numerical results do not agree with the experimental data completely，the heterogeneity of real rock material is simulated effectively with the models and parameters. By analyzing the stress field near the tips of cracks，it is shown that there is no essential influence of processing small holes on the failure mechanism of rock，although the small holes make the initiation angles of wing cracks become large and facilitate the initiation of secondary shear cracks. Lastly，a preliminary numerical analysis is made on the zigzag cracks.

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NUMERICAL ERROR ANALYSIS FOR CONSOLIDATION
EQUATION BY ELEMENT-FREE GALERKIN METHOD

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2004, 23 (18): 3117-3117 doi:

[PDF] 222 KB (949)

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The new numerical method based on element-free Galerkin method (EFGM) and finite element method (FEM) is a promising method to solve the consolidation problem by using element background mesh and shape function from the moving least square approximation. And it may also produce some numerical errors in solving the consolidation equation. In this paper，the FEM-EFGM coupling method is developed and numerically implemented. An error inequality formula for EFGM is presented for consolidation problem based on the Terzaghi’s theory. Then，some influence factors are discussed to reduce the oscillatory errors in EFGM calculation，such as the time factor，the influence of domain and the integral cell structure. In the end，through numerical experiments of the model of two-dimensional stripe foundation，the effect of the integral refined degree of cell structure is validated on both accuracy and stability of the initial pore-pressure in solving the consolidation equation with EFGM. The work of the paper will help to enhance the possibility of the application of EFGM to geotechnical engineering and also provide a new numerical analysis tool for solving the solid-fluid coupling problem.

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RESEARCH ON MULTI-SCALE PREDICTION OF
COAL AND GAS OUTBURST

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2004, 23 (18): 3122-3122 doi:

[PDF] 177 KB (1021)

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The fractal feature of geological structure and the relation between fractal dimension of structure and danger extent of gas outburst are analyzed in three scales of coal field，mining area and stope，respectively. It is shown that geological structures are of fractal features，and there is a positive correlation between fractal dimension of structure and danger extent of gas outburst over the three scales. The results indicate that multi-scale assessment of outburst tendency of coal and gas can be made based on fractal measurements independently or supplemented by other assessing methods.

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ELEMENT-FREE GALERKIN METHOD FOR SIMULATION OF THREE-DIMENSIONAL DISCONTINUOUS INTERFACES

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2004, 23 (18): 3127-3127 doi:

[PDF] 358 KB (702)

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A treatment technique for modeling 3D discontinuous interfaces in elastic bodies by the element-free Galerkin method is presented. In this technique，the isolation effect of discontinuous interface on domain of influence for a Gauss point is dealt by visibility criterion，and contribution of reciprocity between the two faces of discontinuous interface to the system of equilibrium equations is considered. The contributive equation of discontinuous interface to the system of equations is derived and nonlinear iterative algorithms for simulating the contact state of a discontinuous interface are studied. An element-free analysis program for simulation of three-dimensional discontinuous interfaces is developed on basis of the aforesaid discussion. Finally，the program is applied to analyze a cracked cube under the action of well-distributed stress. The result shows that the method and program presented in this paper are reliable and feasible.

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NUMERICAL SIMULATION OF DYNAMIC CRACK PROPAGATION
WITH GENERALIZED FINITE ELEMENT METHOD

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2004, 23 (18): 3132-3132 doi:

[PDF] 326 KB (962)

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An effective and efficient method is presented to simulate 2D dynamic crack propagation problems without any remeshing. The unit decomposition function is constructed over a cracked region by using Shepard formula，visibility criteria and standard FEM shape functions. This set of unit decomposition function are discontinuous across crack lines. With self-defined functions，such as polynomials of any desired degree or asymptotic fields around crack tip，local approximation spaces on patches are built up. Then generalized shape functions are derived，and expected discontinuity is introduced into shape functions and accordingly to displacements field. This method can model fracture problem effectively and be combined with standard FEM procedure intrinsically，and it is called as generalized traditional method. In this method，expanded Newmark nonlinear method is used to solve the dynamic propagation process of crack，and the integral method over virtual extension domain based on energy balance is utilized to compute mixed mode stress intensity factors of static and dynamic fractures. At last，a new auxiliary function is proposed to raise accuracy of solution and improve numerical stability.

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APPLICATION OF 3D ELASTOPLASTIC FRACTURE DAMAGE MODEL TO DETERMINATION OF MININMUM ROOF THICKNESS OF XIAMEN SUBSEA TUNNEL

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2004, 23 (18): 3138-3138 doi:

[PDF] 561 KB (1073)

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In order to verify the stability and the minimum roof thickness of Xiamen subsea tunnel which is under design now，3D FEM analysis is made for 4 profiles along the longitudinal of the tunnel with elastoplastic fracture damage model. Compared with original design of the tunnel，the axial level of tunnel is raised with 2 m and 4 m in the numerical analysis. From the numerical results of stresses，displacements，plastic zones and damage zones of rock mass after excavation，it can be concluded that the tunnel is stable even the axial level of tunnel is raised with 4 m in the numerical analysis

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HOMOTOPY METHOD IN MULTI-PARAMETER INVERSION
OF 2D POROUS MEDIA

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2004, 23 (18): 3144-3144 doi:

[PDF] 391 KB (780)

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According to the principle that the computed response and measured response should be fitted， the parameter inversion problem is reduced to a problem of solving nonlinear equations of point zero in this paper. Then the homotopy method is used to solve nonlinear equation and get solution of the point zero which is the parameter，porosity，to be inversed. The essence of traditional optimal methods，such as gradient method，perturbation method or time-convolution regularization iterative method，is based on Newton iterative method with local convergence. The homotopy method is a newly developed powerful device for solving nonlinear problems. It is introduced to improve the convergent state of Newton iterative method. The basic idea of the homotopy method is to construct a homotopy map with the homotopy parameter，then to track the homotopy path with the homotopy parameter as the variable numerically，and at last，yield the solution. The homotopy method is widely convergent by avoiding the local convergence of Newton iterative method. In this paper，the homotopy method is used to find the solution of inversion problem. For the 2D wave equation in porous media with boundary element solutions，the inversion results obtained by homotopy method are compared with those by the nonlinear optimum method and evolution strategy algorithm. The numerical results show that the parameter inversion by using homotopy method is feasible and effective.

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STUDY ON PERMEABILITY EVOLUATION OF
LIMESTONE IN DRAINAGE TUNNEL

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2004, 23 (18): 3152-3152 doi:

[PDF] 224 KB (1024)

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The original permeability of limestone is very weak，and its excellent permeability results from the cracks rebuilt by groundwater. With the excavation of a limestone tunnel and drainage of groundwater，the velocity of permeability，which is very slow under undisturbed natural hydro-geological conditions，will be improved dramatically. The component solved under low-order resolving reaction condition is drained quickly and fresh groundwater with low concentration is supplied continuously. The evolution of limestone permeability will be accelerated in the disturbed hydro-geological environment，and the low-order chemical reaction will be the prevailed one which will cause significant evolution of permeability in drainage tunnel in the sense of engineering. A parallel board model and PWP equation are adopted to establish the chemical dynamic evolutiom model of limestone permeability in drainage tunnel. The crack is simulated with the parallel board，the dissolution damage of the crack wall is simulated by parallel board model calculated by PWP equation，and the evolution of the surrounding limestone permeability is simulated by introducing the conception of seepage tensor for early drainage period. The presented method can also be used in the evaluation of reservoir leakage，the influence of tunnel drainage on geological environment，stability of rock mass and life of a limestone engineering etc. Finally，an example is introduced .

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EXPERIMENTAL STUDY ON SIMULATION MATERIALS FOR
SOLID-LIQUID COUPLING

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2004, 23 (18): 3157-3157 doi:

[PDF] 301 KB (1100)

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Solid-liquid coupling simulation is developed on the basis of experimental study on solid model material. The problem is solved in this paper that solid model material will collapse when it meets water. At the same time，the problem of the coupling of similarity ratio and the visiblity of different materials is also solved. The mining in shallow coal seams underlying in desert with rich water is simulated by tests and it is proved that the developed materials are suitable for these simulation tests. Different rock bases can be simulated by the model materials with different ratio of materials and different pressure. Solid-liquid coupling occurring in Daliuta coal mine is simulated with the presented material and testing method，and satisfactory result is obtained.

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EFFECT OF PHENOMENOLOGICAL CORRECTION ON
P-WAVE FOR BIOT’S THEORY

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2004, 23 (18): 3162-3162 doi:

[PDF] 317 KB (984)

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In this paper 1D P-wave characteristics are discussed when complex modulus is introduced into Biot equation. It is clear that thermal relaxation attenuation peak and Biot attenuation peak appear on both frequency and temperature domains. These two peaks change while temperature increases. The relaxation peak moves from low frequency side to high one，and Biot peak moves from high frequency side to low one. Also they change when frequency increases. The relaxation peak moves to high temperature side and Biot peak moves to low side. It is found that the combination of thermal relaxation and Biot mechanism leads to increment of wave velocity with two inflection points when its frequency rises. For the same reason，wave velocity decreases and then increases as temperature rises. The results are testified by experiments which are made by the authors. Some published experimental results are also well modeled in this way.

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BOUNDARY ELEMENT METHOD FOR 3D NON-STEADY
HEAT CONDUCTION

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2004, 23 (18): 3168-3168 doi:

[PDF] 456 KB (1503)

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A set of numerical simulation system should be established in order to predict the output and life of underground geothermal energy generation. One of the numerical subsystems is developed for 3D non-steady heat conduction in this chapter，and is verified by analytical solution. Aimed at the limitation of Gauss integral in this system，two special integral methods with high precision are developed.

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FORMULA OF INTERMEDIATE PRINCIPAL STRESS AT FAILURE FOR COHERENT SOIL IN PLANE STRAIN STATE

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2004, 23 (18): 3174-3174 doi:

[PDF] 156 KB (1100)

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Based on the stress state at failure for coherent and frictional materials in plane strain state，it is hypothesized that the intermediate principal stress，s2，makes the Mohr circles of (s1－s2) and (s2－s3) have the same effect degree of cohesion and friction，and then the intermediate principal stress formula at failure for coherent and frictional materials in plane strain state is obtained. When coherence，，is equal to zero，the formula becomes the one of frictional materials，and when frictional angle，j，is equal to zero，the formula becomes the one of coherent materials. At last，the relationships of strength indexes in plane strain state and those in triaxial compressive state are gained.

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MECHANISM OF SELF-ORGANIZED CRITICALITY
IN NON-HOMOGENOUS GRANULAR MIXTURES

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2004, 23 (18): 3178-3178 doi:

[PDF] 306 KB (1071)

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Based on the experiment of critical slope made up of dry sand-gravel mixtures，it is confirmed that self-organized criticality(SOC) in granular mixtures is strongly influenced by non-homogeneity of granular material. Using large-scale coarse grained soil test system，the relative density and direct shear characteristics of sand-gravel mixtures in different size distribution are tested. The occurring condition of SOC and its mechanism are discussed. It is observed that，along with the increment of non-homogeneity，the piled structure becomes more complex，and the sliding resistance among sands grows accordingly. Furthermore，it is concluded from experiments that if the physical characters determined by structure of non-homogenous granular mixtures，the multiform failure states and higher energy dissipation can cause sufficient restraint on disturbing-feedback propagation，granular mixtures will maintain overall stabilization. As a result，a large-scale system can present the SOC as well.

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SAFETY PREDICTION AND TECHNICAL DECISION OF UNDERGROUND MINING UNDER MOUNTAIN VALLEY IN XIANGYU PHOSPHORUS MINE

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2004, 23 (18): 3185-3185 doi:

[PDF] 197 KB (964)

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It is difficult to calculate the accurate displacement of each point in rock mass because of the complexity of the problem. Instead，various approximate methods have been used for this calculation. In fact，the movement of each point at a level of overburden can be regarded as a fuzzy event. In other words，this displacement will take place at a fuzzy probability，and so the theory of fuzzy probability measures can be applied to describe the displacements and deformations of rock mass. In this paper，the application of the fuzzy probability measures to the analysis of the rock mass displacements due to underground mining under the mountain areas in Xiangyu phosphorus mine is described. Available and safe mining scheme is proposed based on the study result.

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CONTRASTIVE STUDY ON INFLUENCE OF DIFFERENCE OF PILE END ROCK-SOIL LAYER ON SUPER-LONG PILE

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2004, 23 (18): 3190-3190 doi:

[PDF] 296 KB (1214)

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Analysis is made on three types of contrastive tests of 8 super-long cast-in-situ piles with different rock-soil layers at pile end. The piles for contrastive tests are 2 piles plunged into and not into bed-rock，2 piles with and without residua at end，2 piles with residua of different thickness，and 2 piles with and without end postgrouting. The study results are as follows. (1) When pile end rock-soil strata changes from soft to dense，the load-settlement curves change from steep shape to gentle one，the failure changes from plunge failure to integer shear failure，the increment of ultimate bearing capacity consists of the increment of ultimate end resistance，and the kind of pile changes from friction pile to end resistance pile，which indicates that end rock-soil layer has significant influence on behavior of super-long pile. (2) The super-long pile with end postgrouting can be regard as super-long pile with pedestal，so that the ultimate end resistance can be expressed by formula including a parameter of resistance increment，and it can also be expressed by the formula of ultimate end resistance for common pile with pedestal. (3) The super-long bored piles，i.e. the pile with length-diameter ratio of 82，penetrating dense stratum，can be regard as end-bearing friction piles with great potential bearing capacity. It is reasonable to confirm bearing capacity of this kind of pile with greater pile head settlement，and this is practicable as long as unbalance settlement is controlled in a limited range.

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HIGH PRESSURE CONSOLIDATION GROUTING FOR TUNNEL
SECTIONS WITH UNFAVORABLE GEOLOGY CONDITION

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2004, 23 (18): 3196-3196 doi:

[PDF] 241 KB (1191)

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The diversion tunnel of Tianshengqiao-2 hydropower station is characterized with large length， considerable embedded depth，high outer-water pressure，very complicated geologic and hydrogeologic conditions. During construction，the unfavorable tunnel sections with fault and fragment，karst caves and blind rivers are strengthened with either the high-pressure consolidation grouting or installing bolts in grouting holes. Consequently，very good results and construction experiences are gained.

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CALCULATION OF SEEPAGE FORCES AND PHREATIC SURFACE UNDER DRAWDOWN CONDITIONS

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2004, 23 (18): 3203-3203 doi:

[PDF] 338 KB (1934)

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It has been proved that the ground water plays a fateful role in the safety factor of slopes. However，in the stabilization design of the TGRZ slopes，the methods adopted for determining the ground water table and hydrodynamic forces during reservoir drawdown are mostly empirical and varied from one project to another. To improve the analysis methods of landslide stability under drawdown conditions，based on the Boussinesq’s differential equation of unsteady-seepage，and Laplace’s transform，a simplified formula is obtained of phreatic surface in landslide mass under drawdown conditions. The simplified formula takes into account the factors of hydraulic conductivity，velocity of drawdown，aquifer thickness and height of drawdown. According to the free surface in landslide mass，the boundary water pressure is defined utilizing the flow net property with orthogonal flow line and equipotent line. It is proved that the seepage force is in equilibrium with the water weight and the water pressure around the slice. The formula of seepage forces is established in slice methods. Finally the effect of above factors on landslide stability is discussed with examples. The result shows that there is a minimum safety factor when the reservoir level is at about 1/3～1/4 of the slope height.

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2004, 23 (18): 3204-3204 doi:

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