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2005, 24 (09): -0 doi:
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2005-09期目录

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STUDY ON TWO-BODY MECHANICAL MODEL BASED ON INTERACTION BETWEEN STRUCTURAL BODY AND GEO-BODY

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2005, 24 (09): -1457 doi:
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The interactions between gravity dams and foundations or arch dams and canyons are important for stability of dams. Based on the conventional interaction bimaterial model of dam and foundation，the two-body mechanical model is presented including the basic concept，method and application scope. The difference of bimaterial model and two-body model is verified by uniaxial compressive tests. The two-body mechanical model of dam and foundation is presented in order to provide a new method for stability analysis of dam and foundation.

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MESO-MECHANICAL EXPERIMENT OF MICROFRACTURING PROCESS OF ROCK UNDER COUPLED MECHANICAL-HYDROLOGICAL-CHEMICAL ENVIRONMENT

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2005, 24 (09): -1465 doi:
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A new meso-mechanical testing system is developed to carry out the experiment of microfracturing process of rocks under the coupled mechanical-hydrological-chemical environment. The image of microfracturing process of the specimen under triaxial or uniaxial compression can be observed and recorded digitally. The loading system is servo-controlled. The microfracturing process of limestone specimen under uniaxial compression with the coupled mechanical-hydrological-chemical environment is recorded by using the testing system. As an example，the results of the specimen soaked in chemical solution of NaCl of 0.01 mol/L and pH = 7 are analyzed. The cracking velocity of cracks at length and width directions is also calculated. The results are compared with those of the specimens without chemical corrosion. The comparison indicates that the testing system is applicable and chemical corrosion can reduce strength of rock and accelerate cracking of cracks.

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RESEARCH ON STABILITY OF ROCK BEDDED SLOPES

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2005, 24 (09): -1474 doi:
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There are alternative stratified joint groups in a stratified rock slope. According to the relation of angles of joints and the slope，stratified rock slopes can be divided into three types：horizontal slopes，reversely inclined slopes and rock bedded slopes. Among these three types of slopes，the rock bedded slopes are most likely to slide. A kind of geo-model material is used to model the bedding slope in this paper. The failure behaviors of cutting slopes in layered rock mass are analyzed by multi-stage excavation of the slope. At the same time，FLAC3D program is used in the model of damage process. The results from the two methods are well coincident. The results show that，in order to avoid the failure of the slope，excavating and supporting should be carried out simultaneously，and anchor bolts should be used firstly in the foot of the slope.

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KINETICS OF SILICATE MINERAL DISSOLUTION AND ITS IMPLICATIONS FOR LANDSLIDE STUDIES

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2005, 24 (09): -1479 doi:
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Silicates are the most important forming-rock minerals of earth crust rock and in exogenous environments，and the dissolution of silicate minerals is universal. In most laboratory experiments，there is an initial period during which nonlinear dissolution behavior is observed and steady-state dissolution rates range from 10－12 to 10－8 mol/(m2·s). Dissolution is nonstoichiometric in most experiments. Bulk dissolution rates are not directly proportional to the surface areas of the minerals studied，but when grains are large compared with the distance among adjacent defects，they will vary linearly with the specific surface areas. Under acidic conditions，dissolution rates are positively proportional to the concentration of hydrogen ion. Organic ligands deriving from organic soluble matter can complex metal ions in solutions and at solid-solution interface，and promote dissolution of silicate minerals. The effect of temperature on dissolution rates follows the Arrhenius equation. In view of the coincidence between the promoting factors of silicate dissolution and landslide occurrence，concentrations of chemical components in watershed surface water may be taken into account in regional evaluation of landslide hazard. Plants can raise the acidity of groundwater and content of organic mater in soil and groundwater runoff rate. The effect of plants on silicate mineral dissolution and landslide preparation is conspicuous. The nonlinear dissolution on slope rockmass scale and the multi-scale preferential dissolution of rock mass are necessary to investigate thoroughly. The concrete problems include identifying and dividing the lasting time of different dissolution states in natural slope water-rock systems，identifying multi-scale damage model of rockmass and transporting mechanism of fluid and chemical components in slope rockmass，and mechanical effect of multi-scale preferential dissolution and so on.

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NEW ALGORITHM FOR PARAMETER INVERSION IN GEOTECHNICAL ENGINEERING

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2005, 24 (09): -1492 doi:
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The principle and the main characteristics of particle swarm optimization，a new simulating evolutionary algorithm proposed recently，are introduced. For the purpose of increasing the local-searching efficiency of the particle swarm optimization，a hybrid approach is presented by combining the particle swarm optimization with simplex method，and the hybrid approach is applied to the parameter inversion in geotechnical engineering. The results of an example show that the hybrid approach is of strong ability to obtain global minima，and its performances are superior to those of single method.

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PRESSURE-DEPENDENT ELASTO-PLASTIC COSSERAT CONTINUUM MODEL AND FINITE ELEMENT SIMULATION OF STRAIN LOCALIZATION

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2005, 24 (09): -1497 doi:
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A pressure-dependent elasto-plastic Cosserat continuum model is presented. The non-associated Drucker-Prager yield criterion is particularly considered. The scalar product of the stress rate and the strain rate is decomposed into the deviatoric and the spherical parts，and the consistent algorithm，such as the return mapping algorithm for the integration of the rate constitutive equation and the closed form of the consistent elasto-plastic tangent modulus matrix，of the pressure-dependent elastoplastic model is derived in the framework of Cosserat continuum theory. The matrix inverse operation usually required in the calculation of elasto-plastic tangent constitutive modulus matrix is avoided，which ensures the second-order convergence rate and the computational efficiency of the model in numerical solution procedure. The strain localization phenomena due to the strain softening are numerically simulated by using the developed model with corresponding finite element method. Numerical results of the plane strain examples illustrate that the capability and performance of the developed model in keeping the well-posedness of the boundary value problems with strain softening behavior incorporated and in reproducing the characteristics of strain localization problems，i.e.，the problems of intense straining development of localization in narrow bands and decreasing load-bearing capacity of the media with developments of the plastic strains.

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RESPONSE SURFACE METHOD AND ITS APPLICATION IN RELIABILITY ANALYSIS OF CONCRETE-FACED ROCKFILL DAM

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2005, 24 (09): -1506 doi:
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The physical parameters of rockfill materials and the loads on concrete-faced rockfill dam (CFRD) are all random variables. They give rise to the uncertainties of stress and deformation of CFRD. Therefore analyzing the structural reliability of CFRD is necessary and reasonable. Because of the complexities of the structure of CFRD and the nonlinear property of rockfill，it is very difficult to carry out the reliability analysis to this kind of structures. In this paper，the response surface method (RSM) for reliability analyses is adopted to calculate the reliability of CFRD and the corresponding calculation formula are derived. 3D nonlinear finite element method is applied to calculate stress and deformation of CFRD. The two-order RSM is applied to the reliability analyses of CFRD. According to a practical example，the calculation of anti-crack and anti-crash reliability of the face slab are conducted and better results are obtained. Compared with other reliability analysis methods，the proposed method is more precise，efficient and convenient.

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DEEP-FOOTING REINFORCING MECHANISM ON REINFORCED SANDY GROUND

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2005, 24 (09): -1512 doi:
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In order to investigate the deep-footing mechanism of reinforced sand，a series of results from plane strain laboratory model test with different number of reinforced layers，are simulated by a nonlinear FEM analysis incorporating an elasto-plastic constitutive model for sand. The constitutive model is developed to have a stress path-independent work-hardening parameter based on the modified plastic strain energy concept. The model ground is made of air-dried dense Toyoura sand，which is either unreinforced or reinforced with numbers of layers and vertical spacing of layers of linear，tensile reinforcing members placed horizontally beneath a strip footing. The results indicate that load-settlement relationships obtained by the FEM analysis are well comparable with those from the physical experiment. It is found out that the peak footing load of reinforced ground increases significantly with the increase of the number of reinforcement layers (the deep-footing effect)，despite that fact the reinforcement length is the same as the footing width，and the contribution by the deep-footing effect is more important than that of the wide-slab effect. In addition，the results also indicate that the progressive failure of model ground with a development of shear bands and the induced tensile forces of reinforcement are reasonably examined by the present FEM analysis，and the deep-footing mechanism of reinforced sandy ground can be well understood.

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NUMERICAL SIMULATION OF SEEPAGE CHANNEL WITH REPA2D UNDER COAL MINING CONDITIONS

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2005, 24 (09): -1522 doi:
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ater-break phenomena occur in some wells in Bajiazi Village，Fuxin Coalfield because of coal mining. The conditions of this case are employed. The hydrogeology qualitative analysis on the groundwater loss mechanism induced by underground mining is carried out. Then numerical simulation is performed with the rock failure process analysis (RFPA2D) code. The change and redistribution of the stress field of the rocks around the stope are studied，and the process from initiation，propagation，and coalescence to rupture of rock crannies around the stope is reproduced. The process shows the transformation and adjustability of the groundwater seepage action and the course of the groundwater leakage to the goaf through the crack. The results of numerical stimulation are consistent with the result of the hydrogeology qualitative analysis，which proves that REPA2D is one of the credible numerical quantitative analysis method to forecast the cranny¢s initiation，propagation，and other hazards(such as the groundwater runoff in this paper). The results of numerical stimulation show that although the goaf and influenced area are in different hydrogeological unit，the groundwater seepage channels are influenced by mining，which provide a favorable hydrogeological condition for the water runoff and accumulation to deep goaf，and make the stope that originally do not possess leakage conditions into a reservoir that can take up prodigious seepage.

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STUDY ON VARIABILITY OF PERMEABILITY OF CORRODED ROCK MASS IN KARST DAM REGION

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2005, 24 (09): -1527 doi:
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Based on the uncertainty risk analysis theory，the depositional environment of the karst dam region is investigated. The method to describe the infiltration characteristics is systematically studied. The variability of permeability and the describing method of the corrosion rock mass are investigated. A new method measuring the variance of permeability is proposed，namely the error spreading function approach based on principle. The extreme values of the statistics parameters such as the width，spacing of the crack，and radius of the karst pipe can be calculated according to principle. And then the variance of permeability is obtained by using the cube law. By discriminating the jointed rock mass and pore karst cave，Kriging¢s random field theory and Vanmarcke¢s relativity theory on the study of geotechnical parameter variance are renewed and improved. Based on the geology statistical data in the field，the variance of permeability of the corroded rock mass in the grouting adit of Qingjiang Shuibuya project in a typical karst region in south China is computed. The proposed method is proved practical and simple. With variance of permeability provided，the random waterpower model can be constituted and then random permeability calculation can also be carried out.

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ANALYSIS OF THE HEATING-UP MECHANISM IN THE COURSE OF THE ROCK RAM

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2005, 24 (09): -1535 doi:
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The energy transformation and heating-up mechanism in the course of the rock ram are analyzed，and the theoretical heating-up formula is acquired. At the same time，the heating-up of marble and sandstone in the course of rock ram are measured by the TVS–2000MKII thermal-image formation system，and then the relation curves of heating-up and quality of rock and those of heating-up and contacting angle are acquired. It is concluded that there are three major factors，that is fracturing of rock，friction and compression of rock，during the rock ram.

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APPLICATION OF EXTENICS IN EVALUATING OF ENGINEERING QUALITY OF ROCK MASSES

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2005, 24 (09): -1539 doi:
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There are various methods for evaluating engineering quality of rock masses，and indexes for different methods are different. Those different factors or indexes in different methods cannot be employed together due to the difference in the evaluation standard of different methods. This leads to the limitation of the traditional evaluation method. Based on extenics，a quantitative evaluation model of rock mass quality of multiple parameters is developed. The advantage of this model is that different factors from different traditional evaluation methods can be considered simultaneously. For example，the factor RQD in RMR can not be used together with the factor Jr in Q system previously because of differences in evaluation standard. But through linear dimensionless method，factors are converted to dimensionless numbers，so those two factors can be used together. Based on the concept of degree of membership and extenics，different factors from different traditional methods are selected and converted to dimensionless numbers. A quantitative method for define the weight of those factors are put forward according to importance of factors. The results of a case show that this evaluation method is feasible.

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APPLICATION OF GEOSTATISTICS IN DETERMINING ROCK MASS PARAMETERS

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2005, 24 (09): -1545 doi:
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Rock mass parameters have the properties of structural and random spatial variance，which result in uncertainty of the parameters. Geostatistics is applied to establish the mathematical model of variation of rock mass parameters. The experimental variance function is obtained by applying weighted polynomial reduction in computer. The ideal parameter values of experimental variance function are determined via cross validation. The ordinary Kriging estimation of rock mass parameters is realized according to these values，and the rock mass parameters in the study field are worked out. Applications show that the established model is reliable，the developed software is feasible and the results are correct.

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ELASTO-PLASTIC NUMERICAL SIMULATION OF SOIL NAILING SUPPORT OF DEEP FOUNDATION PIT

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2005, 24 (09): -1549 doi:
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The stresses and deformations of soils and support structures of foundation pit will change continuously during the course of excavation and supporting. The physical non-linearity of soils and the contact non-linearity of interface between soils and support structures often form the double nonlinear question of civil engineering structures. The mechanical characteristics of foundation engineering are represented based on the detailed description of support system. Then the finite element method and the nonlinear iterative method are presented considering the process of excavation and supporting and the double non-linearity problem. Finally，an illustrative example is analyzed numerically，the relationship between the distribution mode of tension stresses of soil nailing and shear stresses of nailing-soil interface，and the excavation steps are studied. Computational results show that the presented method is rational.

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STUDY ON STRESS-STRAIN CHARACTERISTICS AND DAMAGE RULE OF STRUCTURAL STRENGTH FOR MARINE SOFT SOIL IN HANGZHOU

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2005, 24 (09): -1555 doi:
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Previous laboratory testing studies showed that marine soft soil in Hangzhou is a structural soil，which has obvious structural effect. But in this research，shear shrink phenomenon of the marine soft soil is only observed in shear tests，and the stress-strain curve of the marine soft soil is of hardening of special pattern. These two characteristics differ from typical strain softening of structural soil，so it can be concluded that marine soft soil in Hangzhou is a special structural soil. The pre-consolidation pressure and structural yield stress of the soil are obtained，the rules of structural strength varying with cover depth and damage rules under varying uniaxial compressive pressure are determined. Then，the calculation of structural strength of structural soil is optimized，and the concept structural strength is clarified.

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STUDY ON THE METHOD AND THEORY OF LOAD REDUCTION BY REINFORCEMENT BRIDGE FOR THE CULVERT BENEATH HIGH FILLING

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2005, 24 (09): -1561 doi:
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A new method of load reduction by reinforcement bridge for highway culvert beneath high filling is presented in the paper. According to this method and the principal of load reduction by reinforcement bridge，a “reinforcement bridge”which is consist of reinforcements and a load reduction ditch filled with unpacked soil is built above the culvert to reduce the earth pressure on it. Because the density of soil in the ditch is lower compared to the earth filled on the culvert，the reinforcements on the ditch will deflect down，and in the course of reinforcements deflecting，the vertical earth pressures are transported to the packed soil around the ditch by the reinforcements，as a result，the earth pressures on the top of culvert are reduced. The results of model test show that the vertical earth pressures on the top of culvert with reinforcement bridge are greatly reduced. The results also indicate that the distribution and numbers of reinforcement and load reduction ditch are important factors which affect on the effect of load reduction. Based on the mechanics mechanism of load reduction by reinforcement bridge and the results of model test，a mechanics model of load reduction by reinforcement bridge is presented and three important formulas，including the formula of load calculation，the formula of the numbers and length of reinforcements calculation，are derived from the mechanics model，and an example is given. To prove the effect of load reduction by reinforcement bridge in practice，the stresses of a concrete slab culvert are tested in field and the good load reduction effect is confirmed by the field test results. The results of model and field culvert testing demonstrate that the method of load reduction by reinforcement bridge can be used to highway culverts and other pipes beneath high filling.

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SCATTERING OF ELASTIC WAVE BY CIRCULAR CAVITY WITH LINING IN SATURATED SOIL

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2005, 24 (09): -1572 doi:
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Based on Biot¢s dynamic theory，the method of complex variable functions is used to solve the problem of scattering of elastic waves by circular cavity with lining in saturated soil. The equation of steady-state Biot wave motion is decoupled and reduced to 3 Helmholtz equations by introducing in 3 potential functions. The lining is treated as isotropic elastic material，the control equation of which is decoupled and reduced to two Helmholtz equations by introducing two potential functions. Utilizing the solutions of the potential functions，the expressions of the displacements，stresses and pore pressures of saturated soil and those of the displacements and stresses of lining can be obtained. By using the boundary conditions and continuity conditions between saturated soil and lining structure，the unknown coefficients in the potentials can be determined. The wave number and thickness of lining are analyzed in this paper.

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INVERSION OF FIELD DISTRIBUTION PARAMETERS BY ACOUSTIC TOMOGRAPHY

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2005, 24 (09): -1577 doi:
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Field distribution parameters (FDP)，such as temperature，seepage and stress，are important in civil engineering. It is important to obtain the parameters by inversion of field measurement. According to the relationship between the parameters and acoustic velocity，field distribution parameters can be determined by acoustic velocity distribution which can be calculated by acoustic computer tomography (ACT). Considering of the characteristics of filed parameters distribution，smoothing operator (SO) is proposed in SIRT iterative process of ACT. SO is derived from the corresponding partial differential equation that introduces the contribution of adjacent cells into SIRT process and improves the inversion accuracy obviously. At last an example of frozen temperature field inversion is given to illustrate the effectiveness of the method.

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MODEL TESTING STUDY ON DEFORMATION BEHAVIOR OF SUPER-LARGE PILE GROUP UNDER HORIZONTAL LOAD

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2005, 24 (09): -1582 doi:
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Lizigou large-span bridge which adopts super-large pile group is one of the main projects on the Neijiang—Kunming railway. A model for super-large pile group is developed to study the mechanical action，the distribution feature of internal force and deformation behavior of pile group under horizontal load. Through the model test，some dependence and magnitude of cross section bending moment of piles and horizontal displacement are obtained under different load levels. It is shown that the upper part of pile is affected significantly by the load，the maximum bending moment occurs in the vicinage of cross-connecting of pile and bearing platform，and the value of maximum bending is decreased progressively alone the pile from top to bottom. The mechanical action of the front and rear earth of pile group is different alone the direction of load.

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PROBABILITY DISTRIBUTION FITTING AND OPTIMIZATION OF SHEAR STRENGTH PARAMETERS IN SLIDING ZONE ALONG HORIZONTAL-STRATUM LANDSLIDES IN WANZHOU CITY

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2005, 24 (09): -1588 doi:
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This paper concludes the data of investigation，design，and construction for more than scores of landslides mitigation works in Wanzhou area of the second stage program of large geohazard control and prevention in Three Gorges Reservoir. Based on statistical analysis of shear strength parameters c and j in sliding zone along horizontal-stratum landslides in Wanzhou area and the fitting of probability density function from check method，it draws the conclusion that probability distribution form of cohesion c obeys the logarithm normal distribution，and angle of internal friction j，normal distribution. The probability density function as prior function is used to optimize a little sample of c and j of Guantangkou landslide in Wanzhou area through Bayes method，and the calculated results indicate that variance drops by 37.6% and coefficient of variation by 32%. In this way，the reliability of landslide control can be improved and optimization design will be realized.

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CONCEPT AND DETERMINATION OF LIMIT DISPLACEMENTS OF PRIMARY SUPPORT SYSTEM OF RAILWAY TUNNEL

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2005, 24 (09): -1594 doi:
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Concept of limit displacements of primary support system of railway tunnel are presented，and the method for determining the limit displacements is introduced systematically. The continuum model is adopted，and the cross section pattern and the material properties are used according to the design standard for railway tunnel lining. The limit displacements of the primary support system of railway tunnels are simulated and calculated for the tunnels of different depths in surrounding rocks of different classification. The calculation results are further treated in a statistical manner and compared with the allowable displacements. The limit displacements for single track tunnels and for double track tunnels are discriminated. Criteria are established respectively for crown settlement，horizontal convergence at arch springer and at wall foot. The depth ranges in the original codes are adopted，and the displacement range values are determined by combining the two sets of limit values. A series of limit displacement data are finally determined synthetically，which are consistent with the current displacement criterion for railway tunnel stability.

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DIFFERENCE AND CONNECTION OF TWO KINDS OF ANISOTROPY OF SOILS

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2005, 24 (09): -1599 doi:
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The inherent anisotropy and the induced anisotropy are important characters of soil. There are difference and connection between them. They are both related to the structural character of soils，but the mechanism and conditions are different. The most important difference can be observed from the stress-strain matrix，which has much influence on stress-strain relationship of soils. It can be drawn from the results of true triaxial tests that induced anisotropy has much influence on behavior of soils under complex stress conditions，which should be considered in numerical analysis on soils.

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DISCUSSION ON THE CONSTRUCTION TECHNIQUE OF SPLIT GROUTING IN BODY OF EARTH DAM

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2005, 24 (09): -1605 doi:
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Due to the difference of depth of breast wall in the construction techniques of Zhang¢s and Bai¢s split grouting，the position of original split dam body is different in these two techniques，which will influence curtain shape of dam body，origination point of split grouting，the movement law of grouting fluid and mechanism of grouting. The curtain shapes of Bai¢s split grouting are divided into three types，longitudinal，transverse or oblique and horizontal orientation，and Zhang¢s five types，cross orientation and semi-pile coagulate plate besides the above three types. The difference of these curtain shapes is prominent in the two techniques. For example，Bai¢s longitudinal curtain shape is big in middle and small at two ends，and Zhang¢s is wide at underside and narrow at upside. Bai¢s origination point of split grouting is stochastic，and Zhang¢s is artificially controlled. The generalized physical model of Bai¢s grouting fluid movement is dot-line-side，and Zhang¢s is dot-side. Research on Bai¢s theory and mechanism of grouting are more mature and there are operation codes based on it，but there are no practice by it out off the range stated in operation codes. Zhang¢s continued to use Bai¢s theory，mechanism and criterion of grouting. But whether it is appropriate is to be studied. It is a pressing task to resolve problems of thinner curtain or no curtain at bottom of dam body in Bai¢s and establish the framework of Zhang¢s theory. Accordingly，advices on emendation of the active code are given in this paper.

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PENETRATION EXPERIMENTS FOR NORMAL IMPACT INTO GRANITE TARGETS WITH HIGH-STRENGTH STEEL PROJECTILE

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2005, 24 (09): -1612 doi:
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A series of normal penetration experiments into granite targets with high strength steel projectiles are conducted using light gas gun. The diameter of projectiles is 15 and 20 mm. The final depth of penetration versus striking velocity is acquired，and a new empirical penetration equation is established accordingly. the final depth of penetration predictions from the new penetration equation is identical with experiments. As indicated by experiments，when the striking velocity is about 900 m/s，the projectile is bent. Target dimension effect of scale-model experiments is analyzed. For obtaining availability data，the maxima dimension of projectile must be restricted for a fixed dimension target. The dynamic strength of granite target is estimated，which is many times larger than the unconfined compressive strength. The rigid-body average deceleration is estimated using the law of conversation of energy，and it is in good agreement with numerical results. Static penetration experiment with high-strength steel projectile also is conducted，and the depth of static penetration is very small. It indicates that the stress wave stirred by striking is very important for penetrating.

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APPLICATION OF FRACTURING GROUTING METHOD TO TREAT SOFT FOUNDATION OF OPERATING RAILWAY

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2005, 24 (09): -1619 doi:
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The design method and construction process of fracturing grouting method applied in soft foundation treatment in operating Harbin—Suifenhe railway are introduced in details. The design method of allowable grouting pressure is discussed，and a group of mixture ratios grouting liquid and soluble glass are designed according to geography condition and geologic property of the railway foundation. Several kinds of pressure are designed to sectionalized grouting with three kinds of angles to realize the aims of seepage prevention and reinforcement. The method need small operation site and does not affect the operation of railways with fast concretion speed and well treatment effect.

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IMPACTS OF DETONATING MODE ON BLAST STRESS FIELD OF LINEAR EXPLOSIVE CHARGE

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2005, 24 (09): -1624 doi:
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Analysis of blast stress field is a basic problem of blasting theory research about linear explosive charge. The propagation of blast wave through the linear explosive charge is an important factor which influences the characteristics of the blast stress field induced by the linear explosive charge. Combining the Starfield superposition method with dynamic finite element method，a numerical model of blast stress field research of linear explosive charge is proposed. In this model，principles of Starfield superposition are adopted to realize the propagation of blast wave through the linear explosive charge，and the dynamic finite element method is used to analyze the evolution and formation of blast stress field induced by linear explosive charge in the medium. It can be concluded that the number and position of detonating point play an important role in forming the blast stress field of linear explosive charge，and in engineering practice，it is very useful for improving the blasting effect to reduce the blast time of linear explosive charge by arranging the number and position of detonating points correctly.

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STUDY OF THE PROPER PILE LENGTH IN THE SELF-WEIGHT COLLAPSIBLE LOESS

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2005, 24 (09): -1629 doi:
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The spatial axisymmetric finite element model is established considering the nonlinear of the soil and the interface between pile and soil. Based on the model，a superposition method is proposed to calculate proper pile length in the self-weight collapsible loess，and it is concluded that，when the distribution of skin friction at the upper and lower parts of soil is of same pattern，added pile length DL has no significant influence on distribution of skin friction，but it has on ultimate friction resistance. By this method，the influence of property of the self-weight collapsible loess on pile bearing performance is analyzed. It is observed that：(1) when pile is under ultimate capacity，the depth of neutral point is related to pile length，and (2) the influence of collapse coefficient on rest bearing capacity of pile is nonlinear，and (3) the quantitative range of the depth of neutral point and the added pile length is given.

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CONSTRUCTION TECHNOLOGY OF TBM EXCAVATING THROUGH SECTION OF UNFAVORABLE GEOLOGICAL CONDITION

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2005, 24 (09): -1635 doi:
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Unfavorable geological conditions of highly developed fault fissures and aboundant underground water exist in the TBM excavation of Kunming Shanggongshan water divertion project in west China. The rock mass encountered in most length of the tunnel belongs to Class IV and V according to the applicable national standard. By taking effective measures，such as preceding geological drilling，polyurethane foam injection，increasing water tanks，employing drain pipes of bigger diameter，the problem of water gushing is solved，which，in turn，decreases the risk of collapses at the working face and ensures the safety and progress of TBM operation.