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2005, 24 (22): -0 doi:
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SUBAREA BREAKAGE CONSTITUTIVE MODEL OF ROCK MASS BASED ON CT TEST

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2005, 24 (22): -4003 doi:
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Based on CT test of a certain sandstone under uniaxial compression，the safety zone，the damaging zone and the fracture zone of the sandstone are defined. Then，the divisional criteria by CT number which is used to acquire the binary images of the divisional zones from the CT images at each loading stage are discussed and determined through experiment. On the basis of the divisional criteria，the above three zones of each scanning section at each loading stage are obtained. Furthermore，taking the 5th scanning section for example，its divisional results at each loading stage are given. Then，utilizing the image to measure the technique of mathematical morphology is adopted to analyze the CT number information on these zones in each scanning section individually，which is picked over and calculated through image disposal technology. Moreover，the changing law of CT number on these zones of sandstone changing with the loading process and the procreant conditions of the damaging zone and the fracture zone are presented. Finally，according to the statistical results of CT number on these three kinds of zone obtained at each loading stage，a statistical damage variable based on CT number is defined；and the equation of damage evolution pertinent to this variable is established too. Based on all these data，a constitutive model which can reflect the divisional damage-fracture of sandstone is constructed.

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TECHNOLOGY RESEARCH ABOUT DOUBLE-WAY AND FIVE-STEP CONTINUOUS SHIP LOCKS OF THREE GORGES PROJECT

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2005, 24 (22): -4010 doi:
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[PDF 259 KB] (994)

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The Three Gorges Project(TGP) on the Yangtze River is the largest water resources project in the world. The ship lock of the TGP is schemed as a double-way and five-step continuous ship locks；it has the characteristic of large size and high water head；and the valid size of single-step lock is 280 m×34 m×5 m (length×width×minimum water depth). The ship lock of the TGP is the largest shiplock with highest design total water head in the world. The water level changes range within 135–175 m in up-stream，and within 62.0–73.8 m in down-stream. The design total water head is 113 m and maximum navigation discharge is 56 700 m3/s，through which ten-thousand-ton fleet can pass；and the annual one-way passage capacity is fifteen million tons. The design and research of the TGP initiated in 1950s；it was been construction commencement in April，1994，and it began tried navigation in June 2003. The ship lock of the TGP putting into operation is the synthetical research and applying consequence of many kinds of science and technology. Many technologies about the ship lock are acquired innovation and broke through by a series of science researches.

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DETECTION OF LEAKAGE PASSAGE IN FISSURE ROCK WITH ASSUMPTIVE HEAT SOURCE METHOD

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2005, 24 (22): -4019 doi:
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The concentrated leakage passage in fissured rock is studied with dummy heat source method. The temperature of reservoir water at the bottom is commonly low，whereas the temperature of bedrock increases with depth，so there will be reservoir water leakage around the temperature abnormal area at the dam site. There will be thermal exchange between the leakage and around strata. The leakage water with low temperature will absorb heat from strata；and on the other hand，the strata will discharge heat. According to the theory of energy conservation，these qualities of heat mentioned above are equal. The concentrated leakage passage can be regarded as a dummy heat source；moreover，the temperature distribution in stratum out of the passage is only influenced by the surface layer of passage and not relative to the inner temperature distribution of the passage，namely，the inner temperature distribution of passage is caused by water and the outside temperature distribution is shaped by heat conduction. Then，based on the theory of heat conduction and energy conservation，the temperature distribution in strata can be determined，which can be used to locate the leakage area. A dummy heat source model is proposed to calculate the quantity of leakage water. As an example，a reservoir leakage is analyzed quantitatively.

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EXPERIMENTAL STUDY ON BEHAVIOR OF TRIAXIAL SHEAR TEST OF SATURATED SOFT CLAY TREATING WITH DYNAMIC CONSOLIDATION

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2005, 24 (22): -4025 doi:
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Based on triaxial shear tests (CU) of saturated soft clay of marine deposit，the behaviors of stress-strain relationship of undisturbed soil of marine deposit，remolded soil and overconsolidated soil were analyzed. For the undisturbed soil treated with dynamic consolidation by drainage，the strain softening occurred in process of shearing；and remolded soil presented strain hardening in process of shearing under low confining pressure，but it has strain softening phenomenon under higher confining pressure. The stress-strain relationship curves of soft clay under these three states have better normalization to confining pressure. The test results show that the physico- mechanical properties of undisturbed soil，remolded soil and overconsolidated soil have different improvement in degree. Undisturbed soil treated with dynamic consolidation by drainage has some characteristics of overconsolidated soil；and overconsolidated characteristics of remolded soil treated with dynamic consolidation by drainage are obvious in process of shearing.

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MODIFICATION OF HOEK-BROWN EXPRESSIONS AND ITS APPLICATION TO ENGINEERING

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2005, 24 (22): -4030 doi:
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The importance of study on mechanical parameters of rock mass，and some methods to determine mechanical parameters of rock mass are introduced. Hoek-Brown strength criteria is considered as the authoritative method to get rock mass mechanical parameters from rock mechanical parameters which are got from laboratory. While Hoek-Brown criterion does not give the calculation expressions for rock mass between disturbed and undisturbed. Zhang Jianhai finds this shortcoming and gives his modified expressions，however，only simple average treatment for Hoek-Brown criterion，and the disturbed degree of rock mass can not be described in his modified expressions. H. Sonmez and R. U1usay consider the disturbed degree of rock mass and give their modified expressions，the shortcoming of Hoek-Brown strength criterion and above modified expressions of which are pointed out；and the modificatory coefficients Km，Ks which can take the degree of disturbed rock mass into account are constituted；then the modified expressions for Hoek-Brown strength criteria are brought forward. Km，Ks are based on integrality coefficient Kv，so they can not only reflect the distributed degree of rock mass，but also be got easily. The shortcomings of Hoek-Brown criterion and its former modified expressions are overcome. The modified expressions can determine the mechanical parameters of rock mass between disturbed and undisturbed better. The calculation is carried out through the modified expressions and other methods，respectively，where the study on mechanical parameters of rock mass from Changba Lead-zinc Mine. It is found that the modified expressions in this paper is more suitable to determine the mechanical parameters of rock mass between disturbed and undisturbed；and the result form this method is closer to the measured one. Based on comparative study，the rationality of these modified expressions is further explained.

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ANALYSIS OF THE NONLINEAR DYNAMIC PROCESS OF THE INTERACTION BETWEEN SOFT ROCK AND WATER

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2005, 24 (22): -4036 doi:
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The research on the nonlinear dynamic process of the interaction between soft rocks and water has great values for the studying method of softening process；and it also has some practical significances for the determination of softening parameters. Based on the data analysis of the test results of white and grey colored argillaceous siltstone from the Water Supply Reconstruction Project from Dongjiang to Shenzhen in Guangdong Province of China，in different saturation times，it is found that the softening process of this kind of soft rock is provided as nonlinear characteristics. By applying the fractal analysis method of time series to the interaction system of soft rocks and water；the least needed numbers of dimensionalities (i.e.，variable numbers) for the description of the system is determined by rebuilding the phase space. The test research shows that the microstructure，the connecting strength and the roughness of the grains can be well reflecting the softening features of the saturated soft rocks，and are the key factors for softening process. So，the pore distribution fractal dimension Ds，cohesive force c and internal friction angle j are considered as the necessary variables for the description of the system. And then，the nonlinear dynamic equation of the softening process of the soft rock is established by applying the inverse theory；the undetermined parameters of the equation are obtained by approaching the time series of the three variables to the model by the method of searching for the minimal value of residual sum of squares. Thereby，the nonlinear dynamic process of the interaction between soft rocks and water can be analyzed. The researched results show that the calculated curves of pore distribution fractal dimension of micro-structure，cohesive force c and internal friction angle j of the soft rocks are very close to the test ones，which means that the soft rock-water interaction system has a distinct nonlinear dynamic feature. Meanwhile，the results also show that the model can well predict the varying regularities of microstructure parameters and mechanical properties of saturated soft rocks condition in a certain time scale.

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OPTIMAL ANALYSIS OF CONSTRUCTION SCHEMES FOR SHALLOW LARGE SPAN LONGSHAN TWIN TUNNEL

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2005, 24 (22): -4042 doi:
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With the merits in road line and entrance location choosing，the proportion of twin tunnel is bigger and bigger compared with separated two single tunnels. According to the code for design of road tunnel，the tunnel¢s surrounding rock from supports in calculating for tunnel designing is separated；and the calculated results can¢t reflect construction stages reasonably. So it is necessary to make optimal analysis of construction schemes for twin tunnel. Considering the characteristics such as shallow，large span and double-arch of Longshan tunnel，a finite element analysis program for twin tunnel is established which can simulate the construction process under the three-pilot drift method and benching tunneling method；and the settlement of vault and ground，stress of the middle wall and the stability of the surrounding rock are compared and analyzed；then the advantages of the two methods are compared so as to optimize the practical construction scheme.

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IMPROVED EXPRESSIONS OF TWO-PARAMETER DOUBLE SHEAR UNIFIED FAILURE CRITERION WITH NONLINEAR FAILURE ENVELOPES AND THEIR BEHAVIOR ANALYSIS

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2005, 24 (22): -4048 doi:
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[PDF 281 KB] (937)

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Analysis of the Mohr circles proves that the original two-parameter double shear unified failure criterion has the linear type failure envelope，and the improved failure criteria with parabolic and hyperbolic type failure envelopes are given out in order to describe the rock failure properties，especially the rock tensile property better than the original one. Analyses of loci in the p plane and meridian lines show that the parabolic and hyperbolic type failure envelopes have no influences on the shape of the loci in the p plane，but the shape of the meridian lines are changed from straight lines to curved lines. The limit surfaces of the improved criteria are paraboloid or hyperboloid in the principal stress coordinates. Distances from the conic points to the original coordinate point are smaller than those using the linear type failure envelope. Cone sizes among the criteria using three different envelopes are the criteria with parabolic type failure envelope being the smallest，with hyperbolic type failure envelope being the second，and with linear type failure envelope being the largest.

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REGRESSION ANALYSIS OF INITIAL GEOSTRESS FIELD FOR LEFT BANK HIGH SLOPE REGION AT LONGTAN HYDROPOWER STATION

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2005, 24 (22): -4055 doi:
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Based on the measured data of geostress and engineering-geological conditions in the region of the left bank high slope at Longtan hydropower station，possible factors affecting the initial geostress field are discussed. Under individual effect of factors，the established 3D simplified geological model of the left bank high slope is calculated by FLAC3D. Then，a multivariate regression model is established between the actually measured and corresponding calculated results of geostresses. Through multiple regression analysis，the optimum regression coefficient can be derived. Through the comparison between computed and measured geostress values of measuring points，it has been found that the two are similar in values and directions，which suggests the accuracy and reasonability of the geostress field regression. Thereby，the distribution tendency of initial geostress field of left bank high slope region can be obtained，providing a rational 3D initial geostress field for excavating simulation and analysis of long-term stability of the left bank high slope at Longtan hydropower station.

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STUDY ON ADAPTIVE NATURAL ELEMENT METHOD —
ERROR ESTIMATION

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2005, 24 (22): -4065 doi:
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[PDF 302 KB] (1193)

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Valid estimation of the posterior error is the first step to the implementation of adaptive analysis with the natural element method(NEM). For the successful applications of Z-Z error estimation in the adaptive finite element analysis and the element-free Galerkin method and its simplicity and high efficiency，the implementation of Z-Z method in NEM is attempted. When the NEM is used to solve the solid mechanics problems employing the displacement model，the strain and stress on the scattered nodes cannot be directly acquired form the displacement field because the derivatives on the nodes of the shape function do not exist. What is more，the linear interpolation property of the shape function between the adjacent boundary nodes results shows that the stress/strain is piecewise constant on the boundary. So recovery scheme is performed to extract strain/stress on the nodes and construct a smooth strain/stress field. Moving least squares method is used to extract strain/stress on the nodes from the displacement field acquired from the NEM solution. Then a smoothing stress/strain field can be attained through natural neighbor interpolation employing the recovered strain or stress on the nodes. Numerical examples show that the recovery scheme is feasible；both the accuracy and the convergence of the smoothing stress field are higher. Then difference of original stress field and the recovered stress field is calculated as the error estimation based on the Z-Z method. Numerical example shows that the Z-Z error estimator is feasible，simple and efficient.

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2D AND 2.5D MODELING OF STRATA BASED ON DELAUNAY TRIANGULATION

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2005, 24 (22): -4073 doi:
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[PDF 510 KB] (1416)

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Geological borehole is the main information for engineers to know the distribution of soil strata. In this paper，geological boreholes are abstracted as scattered point data. Each point is the demarcation point between two different strata and a topologic dimidiate data structure is designed for it. Then，the 2D section model of strata was brought out. The model represents the distribution of soil in different depths and each stratum is reconstructed by a series of triangles. In order to represent the horizontal variation of a strata，the 2.5D multi-TIN(triangulated irregular network) model is brought out. The interface between two different soils is also represented by a series of triangles in the 2.5D model. The 2D and 2.5D models were constructed by Delaunay triangulation based on the scattered point data abstracted from boreholes. Then the paper explained the modeling details and method of dealing broken mutation such as fault，dwindles and lens. At last，some assumed classical strata are constructed with the proposed method. The model is convenient for storing，analyzing，visualization and realization by computer. The conventional strata model obtained by corresponding reconstruction algorithms is almost not the final model for visualization. This modeling method based on triangulation can construct the visualization model of strata simultaneously when the reconstructed strata model is accomplished. So it unified the entity strata model and visualization model，which simplifies algorithms and data structure.

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QUASI-STATIC DEFORMATION EQUILIBRIUM EQUATION AND
LOAD PARAMETER IN PREMONITORY PHASE OF ROCK DESTABILIZATION—ENERGY IMPORTING RATE

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2005, 24 (22): -4080 doi:
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[PDF 242 KB] (963)

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Rock¢s quasi-static deformation equilibrium equation in premonitory phase of rock destabilization，which is induced by the energy conservation principle，includes body I¢s elastic energy releasing rate，body II¢s energy dissipation rate and energy importing rate (or generally titled“energy exchanging rate of surroundings and rock”)which is surroundings acting on the system；and full information of rock¢s quasi-static deformation course is covered. Analysis and illustration show it is consistent in discriminating the system stability by energy importing rate -presenting the descending or increasing tendency，and by Dirichlet discrimination law. Outside or surroundings imports energy into rock system when J ＞0；and the system exports energy to outside or surroundings when ； is the dynamic destabilization critical condition of rock，and which can be applied to determine the starting point and ending point of rock destabilization. They can offer scientific basis for calculating releasing energy of earthquake when earthquake or rockburst happens. The quasi-static strain equilibrium equation of rock system is deduced correctly for the first time from whole amount form of total potential energy obtained by imitating elastic stabilization theory.

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DISCUSSION ON A NEW RULE TO FIND LARGEST LYAPUNOV EXPONENT BY SATURATED EMBEDDED DIMENSION

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2005, 24 (22): -4088 doi:
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[PDF 251 KB] (960)

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Based on the analysis of nonlinear dynamics to time series of strain and stress which are tested by MTS to lots of joint systems of sandstone specimens，a new rule to find the largest Lyapunov exponent is established by introducing LE1-m mathematical model and unit-step function. The new rule involves step feature that confirms theoretic condition of finding the largest Lyapunov exponent even more. Value of the largest Lyapunov exponent erected by the new rule is very different to that of the old rule，which will lead to a very different valuing conclusion of chaos to stability of a system. Meanwhile，different sign of the largest Lyapunov exponent will produce different conclusions of system state of which the characteristic has been changed completely. Conclusions of the paper improve robustness to erect LE1 by old rule and are useful to basic theoretic research of chaotic dynamics.

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EXPERIMENTAL STUDY ON DAMAGE EVOLUTION LAW OF ROCK
UNDER CYCLICAL IMPACT LOADINGS

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2005, 24 (22): -4094 doi:
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Three groups of experiments are designed to study the damage evolution law of rock under cyclical impact loadings. In these experiments，different grades of confining pressures，impulsive forces and times of shock are considered to have some effects on the damage degree evolution of rock. Simulating impact loadings to marble test cylinders have been accomplished on compression test machine；and the velocities of ultrasonic in damaged marble test cylinders are actually measured. The variation of ultrasonic velocity is used to describe the damage degree evolution of rock under the actions of cyclical impact loadings. The influence regulation of impulsive force and times of shock on the damage degree evolution under cyclical impact loadings are obtained. The results illustrate that the damage degree evolution of marble test cylinders have close correlations with confining pressures，the grades of impulsive force and the times of shock. Under the same confining pressure grade，the damage evolution is determined by the times of shock and the grade of impulsive forces. When the grade of impulsive forces keeping unchanged，the damage evolution is determined by the times of shock and the grade of confining pressures. As confining pressure being raised，the damage depth evolution speed of marble test cylinder under the same cyclical impact loading is reduced with the increasing of times of shock. It is also proved that the effect of confining pressure on the damage degree evolution is affected by the grades of impulsive force under the same shock times. The existence of confining pressure increases the impulsive strength of marble test cylinders.

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MODIFIED GREY SYSTEM FORECASTING MODEL AND ITS APPLICATION FOR ANALYZING INFORMATION OF LANDSLIDE MONITORY

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2005, 24 (22): -4099 doi:
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[PDF 374 KB] (973)

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Based on the all data GM(1，1) model of grey system，different modified models are set up in their given order through out the course of metabolism，residual error modified of different rank，and weighted modified. In setting up the model，unequal intervals in the data of the actual measure are considered；and equal intervals of grey system forecasting model are extended to unequal ones. Together with the information of landslide monitored in Lailong Mountain in Fuyang City，the inclinometer B14，which lies in the active slide area and lasts four typical sliding phases，is studied in the course of where the displacement in sliding zone is forecasted and analyzed comparatively by the computational programs of various models. The result of model precision test shows that the residual error of two rank and weighted modified GM(1，1) model can greatly improve the forecasting precision and adjustability.

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CONSTRUCTION SIMULATION AND MONITORING DATA ANALYSIS OF HIGH CUT SLOPE WITH FAULTY GEOLOGY

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2005, 24 (22): -4106 doi:
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[PDF 410 KB] (984)

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Stability of high cut slope is influenced significantly by many factors such as rainfall and excavation， especially with faulty geology. Therefore，it is necessary to simulate excavation operation and analyze monitoring data in time for dynamic construction design. As a typical example，K108+208～+466 high cut slope in Beijing—Zhuhai Expressway with coal geology is calculated with finite element method (FEM) and monitored during excavation. FEM stress and displacement results are in good agreement with in-situ monitoring data，both indicating the trend of deep landslide. Further，potential sliding surfaces are determined by slope internal displacement and sliding rate. The influence of rainfall and excavation on slope displacement is proven immediately by increasing slope deformation rate. Finally，combining FEM computation with monitoring analysis is the main process of dynamic design which guides construction and assures safety.

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STUDY ON REDUNDANT REGULATION OF UNDERGROUND DIGGING
BLASTING VIBRATION OF ZHOUNING HYDROPOWER STATION

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2005, 24 (22): -4111 doi:
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The underground workshop of Zhouning Hydropower Station is a large chamber with size of 66.82 m× 17.90 m×42.20 m(L×H×W )；its wall rock is lengthened crisp and whole granite. In order to protect rock anchor and girder wall，safety monitoring of exploding tremor is considered for the wall rock after adopting presplit blasting to protected layer in the courses of blasting and digging. This paper analyzes the domino effect of blasting tremor that blasting brought，acquires attenuation coefficient of earthquake wave and equation coefficient k by using the regression analysis method；summarizes the transmitting rule of blasting earthquake wave indwell the crisp and whole granite，consequently. The scathing extent is deduced，which is used to supervise the upper preferences and the scheme of safety command. The transmitting parameter of earthquake wave can provide reference to similar engineering.

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BEHAVIOR ANALYSIS OF INITIAL POST-BUCKLING OF SOCKETED FILLING PILE WITH HIGHRISE PILE CAP BY m METHOD

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2005, 24 (22): -4115 doi:
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To investigate the initial post-buckling behavior of socketed filling pile with highrise pile cap being widely used in bridge engineering，the pile shaft is idealized as a partially supported beam on Winkler foundation. And based on the m method adopted by current criterion，the total potential energy of the pile-soil system is set up. Then，by using the principle of minimum potential energy and perturbation approach，the unified variation expression of critical load during initial post-buckling is deduced with the stability of equilibrium path under three assumed conditions and discussed，respectively. The result shows that，the bifurcation points are symmetric and stable or unstable depending on the stiffness ratios of pile to soil，free length at the top and other pile-soil system parameters. Usually，stiffness of surrounding soil helps to bring more stable initial post-buckling equilibrium path. However，when the stiffness of pile shaft keeps constant while the soil becomes weaker，unstable initial post-buckling equilibrium paths tend to happen more often if the pile tip isn′t socketed into bedrock.

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MESOSCOPIC NUMERICAL TESTS ON FAILURE PROCESS OF HETEROGENEOUS CONCRETE

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2005, 24 (22): -4120 doi:
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A mesoscopic numerical model to study the progressive failure process and the nonlinear mechanical behavior of heterogeneous concrete is established in combination with an elastoplastic anisotropic damage constitutive for concrete mesoscopic element. The proposed model is based on the mesoscopic structure characteristic of concrete，in which the Weibull distribution function is adopted to introduce the material heterogeneity，and the constraint function method for contact problems proposed by Bathe in 1997 to treat with the interaction between different objects such as the end constraint between specimen and end platens. By using the established numerical model，numerical tests about the progressive failure process and the nonlinear mechanics behavior of concrete specimen under compression and tension loading are then serially carried out. The obtained numerical results are basically corresponding with those of other researchers，thus further verifying the validity of this proposed mesoscopic numerical model. The proposed numerical model provides a new method to study the progressive failure process and the nonlinear mechanical behavior of heterogeneous concrete under complex loading.

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DISPLACEMENT BACK ANALYSIS BASED ON SUPPORT VECTOR MACHINE AND SIMULATED ANNEALING

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2005, 24 (22): -4134 doi:
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A displacement back analysis is proposed by combining the support vector machine and simulated annealing. Firstly the support vector machine is used to substitute the time-consuming finite element analysis；and secondly simulated annealing is used for the optimization of objective function for fear that the search often falls in one of the minimums and cannot go any further when the conventional mathematical optimization methods are employed. The feasibility of this approach is verified by back analysis of the mechanical parameters of a slope.

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SUPPORT VECTOR MACHINE MODEL FOR PREDICTING SAND LIQUEFACTION

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2005, 24 (22): -4139 doi:
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Based on study of main factors that have great influence on sand liquefaction，the support vector machine(SVM) model of sand liquefactions was established. The nonlinear relation between sand liquefactions and influencing factors was learned from the finite empirical data by SVM model. Then the model was applied to the practical engineering. The results show SVM model of linear kernel function is not enough effective to found the mapping between classification of sand liquefactions and influencing factors；but polynomial kernel functions and radial based function(RBF) kernel can correctly evaluate the classification of sand liquefactions.

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STUDY ON RELIABILITY OPTIMIZATION OF SEGMENTS LINING IN SHIELD TUNNEL

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2005, 24 (22): -4145 doi:
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[PDF 239 KB] (971)

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Based on the geometrical meaning of structural reliability index，the reliability optimization model of segments lining in shield tunnel is proposed. Furthermore，the program is developed according to complex optimization algorithm. The numerical example is provided to demonstrate the better efficiency and accuracy of the optimization model，which avoids the performance function¢s partial derivative to the random variable，than those of first-order approximation methods. The value of equivalent standard normal distribution variable at checking point is expressed with the checking point coordinates and the statistics value of original random variable，which avoid the R-F(Rackwitz R. and Fiessler B.) equivalent normal transformation of each iterative calculation at checking point. In the example analysis，the optimization model is very suitable to acquire the reliability index of segments lining in shield tunnel where the performance function is highly nonlinear and implicit；and the optimization is a new approach to analyzing of underground structure reliability.

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CONSOLIDATED-UNDRAINED TRIAXIAL TEST STUDY ON STEADY STATE STRENGTH OF SAND

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2005, 24 (22): -4151 doi:
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The steady state strength theory is significant in earth structure aseismatic study. The steady state strength concepts，the consolidated-undrained triaxial shear test method and the test results are introduced. From the test and analysis，the existence and uniqueness of steady state line are demonstrated；and the steady state line equations are derived. An approach to determining the steady state strength qss from consolidation pressure s3 and relative density Dr is presented；and the physical implication of steady state friction angle is revealed.

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EXPERIMENTAL STUDY ON VIBRATION EFFECTS OF GROUND
DUE TO SHALLOW TUNNEL BLASTING

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2005, 24 (22): -4158 doi:
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[PDF 237 KB] (1454)

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Taking the project of Renhechang shallow tunnel for Chongqing—Huaihua railway as the background，the field experiments of vibration effects of the ground in tunneling blasting have been done. Based on the measurement of the waveforms of the vibration velocity in different distances away from the tunneling blasting sources on the ground，the vibration characteristic of the ground and its varying laws are studied. Four blasting experiments for the shallow tunnel were carried out and twenty-seven waveforms of measured point vibration were obtained. The results of the tests and analysis show that：(1) the seismic effect of cutting hole blasting is the most intensive and its vibration intensity is over two times greater than that of the other blast-holes blasting；(2) the vibration velocities of the ground resulting from relief，breast and trim holes blasting do not always become greater with the increase of their single period charges；(3) the excavation region of the shallow tunnel may cause the hollow effect of ground vibration in tunneling blasting；and (4) the blasting vibration effect along the tunneling direction can be forecasted by Sadov¢s formula，but the formula is not suited to the forecast of the opposite direction. Moreover，for Renhechang shallow tunnel，the attenuation parameters of seismic waves along the tunneling direction are K = 232.8 and a = 1.90.

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CALCULATION AND ANALYSIS OF CONSOLIDATION THEORY OF GROUND BY PARTIALLY PENETRATED SAND DRAIN

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2005, 24 (22): -4164 doi:
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[PDF 267 KB] (871)

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The ground by partially penetrated sand drain is turned into an equivalent-double-layered ground with the general solution of average degree of consolidation；and its analytical solution of one-dimensional consolidation is worked out，and furthermore，the average degree of consolidation is gained. Based on this solution，the present existing solutions，and finite element method，these relevant programs are coded. The influence of rw on the consolidation process is investigated；and the relevant results are prepared in graph forms；and the applicability of all these solutions is evaluated. It is shown that the curves of U - Tv are more actual which is drawn by this solution in comparison with the others in the case of PTPB or PTIB. And the solution given in this paper meets the requirements of project.

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NONSTATIONARY PROBABILISTIC DYNAMIC RESPONSE ANALYSIS OF EFFECTIVE STRESS OF NONLINEAR SOIL PROFILE

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2005, 24 (22): -4172 doi:
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[PDF 503 KB] (877)

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The nonstationary probabilistic seismic response was carried out via pseudo excitation algorithm combined with finite element method under uniform nonstationary seismic environment. The evolutionary power spectral density (PSD) of acceleration at the engineering bedrock was handled as the nonstationary pseudo input. Shear modulus and damping ratio were obtained iteratively from the Hardin-Drnevich constitute relationship accounting for the nonlinearity of soil and the effect of pore pressure. Also，the performance of four techniques，using different approximations to estimate the equivalent peak value of shear stress and strain，were investigated for the purpose of determining the equivalent shear modulus，damping and excess pore water pressure induced by seismic loading，in which the equivalent peak value is computed in terms of its standard deviation and the corresponding peak factor. It is found that the interpolation method based on probabilistic average approach is appropriate compared to the deterministic method. The analytic results indicate that the dynamic response of liquefiable soil is time-dependent due to the cumulation of the excess water pore pressure and should be considered as nonstationary process.

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EXPERIMENTAL STUDY ON FATIGUE FAILURE OF INTERMITTENT JOINTED ROCK MASSES SUBJECTED TO REPEATED STRESS WAVE

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2005, 24 (22): -4180 doi:
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The fatigue failure behaviors of intermittent jointed rock masses subjected to repeated stress waves are investigated on the basis of experiments. In order that failure modes in the experiments can be easily observed，all specimens are made of transparent organic glass plate. A tailor-made exploder is used to offer dynamic loads. For static loading，axial stress is provided by a testing machine，and lateral stress is given by a set of jack. Affecting factors which may influence the dynamic fatigue failure property of rock mass，such as joints angles，stuffing characteristics and lateral pressures，are analyzed. Experimental results indicate that damage accumulation of intermittence rock mass is markedly related to the intersection angle between joints and propagation direction of stress waves，and damage distribution will be more nonuniform with the increase of that angle. When the intersection angles are small，the initiation of wing cracks near the tip of joints and damage accumulation are even correspondingly. But for larger intersection angles，fracture and damage are localized on the side of incident waves. For different stuffing cases，results show that joints stuffed with fillings are more favorable for the propagation of stress waves than that of unfilled；but stuffing may decrease the rate of damage accumulation and increase the fatigue life of rock mass. Also，the rate of damage accumulation is controlled by lateral pressure，which decreases along with the increase of lateral pressure. These experimental results show that the fatigue failure of intermittent jointed rock masses are quite complex.

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EFFECT OF INITIAL GEOMETRICAL IMPERFECTIONS ON STABILITY OF ULTRAHIGH PILLAR

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2005, 24 (22): -4185 doi:
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[PDF 195 KB] (988)

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A simplified mechanical model of ultrahigh pillar with initial geometrical imperfections was established and the stability of the system was discussed by means of initial deflection function，the stress-strain relation of rock，the strain-curvature relation，static balance at elastic stage and at elastoplastic stage. The compliance relations between the stability of ultrahigh pillar and initial geometrical imperfections were established and ultimate load of ultrahigh pillar with initial geometrical imperfections were obtained at elastoplastic stage. The results show that the general deflection of ultrahigh pillar with initial geometrical imperfections is the product initial deflection function and under the load of upper rock mass at elastic stage；and the maximal deflection relates to initial deflection imperfections factor f0 and it increases with the increase of f0 before reaching critical state；and that the ultimate load of ultrahigh pillar decreases with the increase of initial deflection imperfections factor f0 at elastoplastic stage. Furthermore，an example was calculated based on Dongguashan copper mine；the estimated results correspond to practical experience so as to provide basis for mining order and arranging stope.

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FIELD TESTING STUDY ON STRESS RATIO OF PILE TO SOIL IN COMPOSITE GROUND OF DRY JET MIXING PILES AT YINJIAZHUANG—ZHONGCHUAN EXPRESSWAY

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2005, 24 (22): -4190 doi:
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[PDF 325 KB] (944)

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Combined with the practical project by using dry jet mixing(DJM) piles to treat the saturated loess under the Yinjiazhuang—Zhongchuan expressway in Gansu Province，two typical sections were selected to test the stress of the pile and the soil with the pressure gauge in the composite ground. In the two sections，one is the floating pile composite ground，the other is the end-bearing pile composite ground. On the basis of the test data，calculated the stress ratio of the pile to soil and the bearing capacity is calculated. The results show that：(1) the stress of the pile and the soil in the end-bearing pile composite ground is larger than that in the floating pile composite ground when the upper load is the same；(2) the stress ratio of the pile to the soil is focused on 3–8 in this case；(3) in the two kinds of composite ground，the calculated bearing capacity being brought into play is more closer to the real load if the soil is supposed to fail first；(4) the failure mode of the composite ground under flexible foundation is the initial soil failure，then the failure of the whole composite ground is induced.

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RELIABILITY ANALYSIS OF VERTICAL BEARING CAPACITY
OF SINGLE SQUEEZED BRANCH PILE

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2005, 24 (22): -4197 doi:
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[PDF 184 KB] (1272)

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At first，an expatiation of the virtue of squeezed branch piles is made. On the basis of the plenty of test data of squeezed branch piles，the reliability analysis of the vertical ultimate bearing capacity of single pile is made by using the limit state equation of dimensionless random variables. The reliability index b is calculated by the method of JC method. What is more，the influence of loading effect ratio，general safety factor and different load compositions on the reliability index is also discussed. At last，based on the analysis of the data of squeezed branch piles test，the conclusion that the reliability index b of squeezed branch piles outclasses that of the same section piles is drawn.

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ANALYSIS AND APPLICATION OF ROCK DAMAGE MECHANISM
AND SCALE EFFECT ON JOINTS DISTRIBUTION
WITH NONLINEAR DYNAMICS

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2005, 24 (22): -4202 doi:
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[PDF 94 KB] (1038)

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