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2005, 24 (15): -0 doi:
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2005-15期目录

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ON ENERGY ANALYSIS OF ROCK FAILURE

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2005, 24 (15): -2603 doi:
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On the viewpoint of energy，the deformation and failure process of rock are studied. The behavior of energy dissipation and energy release during this process is also discussed. Theoretical and laboratory experimental studies indicate that energy plays an important role during rock deformation and failure. Rock failure is caused by the abrupt energy release，which is the catastrophe of energy dissipation under a certain condition. From the viewpoint of mechanics，rock deformation and failure process are processes from local dissipation to part failure and eventually to whole catastrophe；in addition，from the viewpoint of thermodynamics，this process is an irreversible process which includes energy dissipation and energy release. Current mechanics theories emphasize the energy dissipation and part breakage，however，the main feature of rock failure is energy release. Therefore，it is necessary to consider synthetically the effect of energy dissipation and energy release. Laboratory studies in the paper also demonstrate that the rock failure feature can not be described by the stress or strain strength. It is observed that the failure types of rock samples are different from each other even if the stress-strain curves are almost uniform，but the amount of energy release of rock samples is distinct. Consequently，the rock deformation and fracture process can be well described from the viewpoint of energy.

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DETERMINATION OF SLIP SURFACE IN SLOPE BASED ON THEORY OF SLIP LINE FIELD

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2005, 24 (15): -2609 doi:
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A method to search for the slip surface in slope through finite element result based on the theory of slip line is improved；and the influence of the flow rule on the slope stability is studied based on this method. In this method，the elastic area and plastic zone can be distinguished and the different flow rules can be considered. The methods to protract the orientation field of slip line and trace the slip line from any point in export portion are brought out. The slip line of which the safety factor is least，is the critical slip surface. The examples have shown the reliability of the method. The study indicates that the flow rule has small influence on the stability of the slope without restriction；however，the critical slip surface may be different. If there are loads on the top of the slope，especially the loads are crucial，the flow rule can influence both the safety factor and the slip surface remarkably. If the associated flow rule is adopted，the stability of the slope may be overestimated.

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DETERMINING THREE-DIMENSIONAL CONNECTIVITY OF ROCK MASS DISCONTINUITY BY PROJECTION

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2005, 24 (15): -2617 doi:
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Three-dimensional connectivity of rock mass fractures is an important parameter which has the connotation of evaluating rock mass stability. It has the meaning of hydro-rock mechanics which is totally different from the meaning of connectivity related to the hydrogeology. Because of the randomness of fractures in rock mass，it is very difficult to obtain the three-dimensional connectivity of rock mass fractures by general method. A new method to obtain the three-dimensional connectivity of rock mass fractures is described based on the in-situ engineering rock mass fractures of three-dimensional network numerical modeling to obtain the three-dimensional connectivity in special dip direction and key section of engineering rock mass by ideal section plane projection. A computer programming is written by authors to realize the calculation；and its result is directly applied to practical engineering.

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STUDY ON BOTDR-BASED DISTRIBUTED OPTICAL FIBER STRAIN MEASUREMENT FOR TUNNEL HEALTH DIAGNOSIS

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2005, 24 (15): -2622 doi:
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[PDF 96 KB] (2013)

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The Brilliouin optical time domain reflectometer(BOTDR) is a newly developed measurement and monitoring technique，which utilizes Brilliouin spectroscopy and optical time domain reflectometer to measure strain generated in optical fibers and distributed in the longitudinal direction. Hence，the BOTDR has the characteristics of distributed measurement，long distance，high precision and durability. In this paper，the basic principle and features of the BOTDR are briefly introduced；and taking Nanjing Gulou Tunnel as a case，the technical and monitoring schemes of BOTDR are presented；the installation of sensing optic fiber and the temperature compensation method are introduced；the influence of environmental factors such as temperature and vibration on the measurement results is discussed. Finally，the monitoring results of the tunnel are analyzed and the health diagnosis is given. The monitoring achievements demonstrate that the BOTDR is a feasible and powerful technique for the strain measurement and health diagnosis of the tunnel engineering.

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FINITE ELEMENT BACK ANALYSIS METHOD FOR EVALUATING STOCHASTIC SEISMIC CHARACTERISTICS OF BEDROCK

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2005, 24 (15): -2629 doi:
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With considering the earthquake motion as a stochastic process，based on the basic principles of dynamical analysis by using finite element method，formulas for the back-evaluating stochastic seismic characteristics of the bedrock from the stochastic seismic characteristics of the ground surface are derived by using the impulse-response function，the theories of random vibration，and the principles of Fourier transform. A method of finite element back analysis for this purpose is put forward. By using this method，the stochastic seismic characteristics of the bedrock could be calculated from the stochastic seismic characteristics of the ground surface. A numerical example shows that the ground changes the frequency composition of earthquake motion and has an obviously amplifying effect on seismic motion of the bedrock. The seismic motion of the bedrock should be input to earthquake motion during the analysis of earthquake resistance of underground structures.

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STUDY ON EVOLVING CELLULAR AUTOMATA(ECA) TO MODEL CRACK OF BRITTLE ROCK

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2005, 24 (15): -2634 doi:
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Based on the theory of cellular automata，evolving cellular automata(ECA) model is set up considering the fundamental of rock mechanics. In the ECA model，the strain-stress relations of the brittle rock are considered to agree with the perfect elastic constitutive law in meso-cosmic view，but in the macroscopically view，the brittle rock is a kind of nonhonmogeneous material and its nonhonmogeneous distribution is assumed as Weibull distribution. Breaking out the limit that the CA model only consists of one kind of cell，a neighborhood model with two kinds of cells is brought forward in the ECA model. There in，one is the node cell and the other is triangular cell. Displacement，force，stress and strain are taken as basic variables of the system. The tensor and scalar are defined at the triangular cell and the vector at the node cell. In the ECA system，the triangular cell and the node cell are taken as neighborhoods with each other and evolved according to the local international rules. The tensile failure and shear fracture are taken into account by the triangular cell¢s evolving followed the failure rules which are on the basis of the modified Mohr-Coulomb criteria. According to the above-mentioned method，the simulation of the loading and failure process are carried into execution.

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LANDSLIDE HAZARD ASSESSMENT AROUND A PAST LANDSLIDE SITE

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2005, 24 (15): -2640 doi:
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The slope failure and landslide hazard will possess the same properties within a range with the same engineering geological conditions. For landslide hazard assessment of a mountainous area，the study of past landslide is very important for evaluating landslide hazard around the past landslide site. Based on the study of mechanism of a past landslide taken place in Kumamoto of Japan，this study firstly proposes the mechanical parameters for landslide hazard evaluating using a 3D slope stability method. For each slope unit in the study area，the critical slip surface，which gives a minimum safety factor of a slope，can be obtained. The affected streams and range of possible landslide masses are analyzed based on the damaged range of the past landslide. Over layered with the layers of infrastructure in geographical information system(GIS)，this hazard map indicates which buildings and road sections are still in the dangerous area.

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DAMAGE CONSTITUTIVE EQUATIONS FOR ENERGY DISSIPATION AND ITS APPLICATIONS TO STABILITY ANALYSIS OF SURROUNDING ROCK MASS OF CAVERNS

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2005, 24 (15): -2646 doi:
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The constitutive model is formulated within the irreversible thermodynamics framework，appling the basic principle of energy dissipation；the effective strain of the elastic-damage，the evolution equations of the damage and the yielding criterion of the damage are derived. The constitutive equations for the damaged rock mass are written according to the principle of strain energy equivalence between the raw rock mass and damaged rock. The damaged rock mass is modeled by using the constitutive laws of the effective undamaged rock mass in which the nominal stresses are replaced by the effective stresses. An additive decomposition of the total strain into elastic and inelastic parts is adopted. The elastic part is further decomposed into two portions，one is recoverable elastic distortion and the other is unrecoverable elastic distortion，namely elastic damaged distortion. The inelastic part is also decomposed into two portions，one is plastic distortion and the other is crack closure distortion. The proposed models are applied to analyze the stability of caverns of which the result gives the damage values and zones of the surrounding rock mass of caverns. These values and zones show where damage and fracture occur. The paper supposes that when the damage value is equal to 1.0，the rock mass is defined as fully fractured. And then the method changes to macro-fracture mechanics. So the method provides some theoretical foundations for the micro-mechanics and some ways of the macro analysis in the fields of rock mass engineerings.

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EFFECT OF CROSS-CORRELATIONS AMONG SOIL PARAMETERS ON RELIABILITY OF REINFORCED RETAINING WALLS

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2005, 24 (15): -2654 doi:
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The influence of cross-correlation among three pairs of soil parameters on the reliability of reinforced retaining wall under various destructive modes are discussed. The three pairs of soil parameters are as follows：(1) the cohesion and friction angle；(2) the friction coefficient between fill and geotextile，and friction angle of fill；and (3) the friction coefficient between fill and ground，and friction angle of fill. The reliability indexes are increased if the negative correlation among parameters is considered. The reliability indexes are reduced or increased if the positive correlation among parameters is considered. The anti-slide reliability is reduced when the positive correlation among the friction coefficient between fill and ground and the friction angle of fill is applied. In contract，the reliability is increased when the positive/negative correlation among other parameters is applied. Overturn failure of the reinforced retaining wall is highly impossible if the stability requirements of other destructive modes have been satisfied. The cross-correlation between parameters is inherent character of soil，whether to consider it depends on the significance of project.

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STUDY ON RHEOLOGICAL PROPERTIES AND MODEL FOR GYPSUM BRECCIAS

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2005, 24 (15): -2659 doi:
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The creep tests of gypsum breccias are done；and the experimental creep curves and isochronous stress-strain curves are got，which display the properties of nonlinearity and accelerated creep. In order to describe these properties of gypsum breccias comprehensively，two viscous components of non-Newtonian fluid are put forward and are combined with conventional components to gain a new multiple rheological model. According to the new model，the corresponding one-dimensional and three-dimensional creep constitutive equations are deduced. Then the experimental creep curves are simulated using the new rheological model；and the results indicate that the new model can effectively describe the whole rheological process of gypsum breccias.

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RESEARCH ON CRACK DEVELOPING PROCESS IN NON-INTERPENETRATED CRACK MEDIA BY USING CT

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2005, 24 (15): -2665 doi:
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Non-interpenetrated crack concrete specimens are used to study the crack developing process in non-interpenetrated crack media under uniaxial loading. The specimen is a cubic pillar of 10 mm×10 mm×21 mm in size with non-interpenetrated pre-existing cracks which are inclined to the loading direction at 30°，45°，60°，90°，respectively. The in-time CT scanning is made in the process of uniaxial loading and 3D CT images are reconstructed to detect crack developing process. Based on the CT images，damage isoline of scanning section is drawn to describe quantitatively the process of crack developing. The study shows the different effects of two kinds of damage (crack and micro crack) on crack developing process.

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CONTRAST EXPERIMENTAL STUDY ON COOLING EFFECT AND MECHANISM BETWEEN CLOSED AND OPEN RIPRAPPED-EMBANKMENTS

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2005, 24 (15): -2671 doi:
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In construction and maintenance of road engineering in cold regions，permafrost has been the mainly influencing factor in embankment stability. The cooling effect of the riprapped embankment on the soil beneath has been recognized. In this paper，the differences of the cooling effect and mechanism between the closed and open riprapped embankments have been compared through the laboratory test. It can be concluded that the cooling rate of the open model is faster than that of the closed one，but as far as a long-term effect is concerned，the closed one¢s cooling capability is larger under the condition of the experimental temperature. Furthermore，by analyzing the changing correlation between the top temperature and the temperature difference through the top and bottom of the riprapped layers，taking consideration of the temperature field in the riprapped layers，it is found that the cooling mechanisms of the two embankment models are quite different from each other. Namely，the cooling effect of the closed embankment model on the soil beneath mainly relies on the changing of the thermal conductivity of riprapped layer，which is caused by the changing of the inside nature convection，but that of the open model relies on the way of heat-transfer enhancement because of the inside forced convection induced by the low temperature wind outside. But the two ways of convection exist together because of the effect of many factors in actual engineering；therefore，both of the two models have good application perspective in permafrost regions where mean annual air temperature is subfreezing.

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RESEARCH ON BEARING CAPACITY OF CRETACEOUS ARGILLACEOUS SILTSTONE

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2005, 24 (15): -2678 doi:
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Cretaceous argillaceous siltstone in Changsha district is a kind of soft rock with the features of weak diagenetic process，and it is suspcetible to weathering and can be easily disintegrated. The potential bearing capacity of this rock is relatively higher，having softing coefficient less than 0.75 with low pore rate，water absorptivity，and inferior crack connection. Testing study is made on the basic mechanical property of this rock，which includes uniaxial compression，loading test and high pressure pressurementer test(PMT). Through the testing and analysis，it is found that the bearing capacity evaluated with “Code for Design of Building Foundation”(GB50007–2002) is lower than actual one. The problem—how to determine the total resistance of embedded section of argillaceous siltstone with various testing methods and different codes has been discussed. Determining the bearing capacity design value of rock，using the uniaxial compressive strength standard value under natural moisture，the coefficient of exertion is varied with different embedded depth-diameter ratios(hr/d). An improved formula is given to calculate the total resistence of embedded section. The study results which comparatively agree with the practice is instructive for design and further study.

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EFFECTS OF SUPPORTING FOR UNDERGROUND OPENING CONSIDERING COUPLED HYDRO-MECHANICAL ACTION

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2005, 24 (15): -2683 doi:
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Firstly the momentum equilibrium equation，the continuity equation for water are established. Secondly by using the Galerkin method all the governing equations are discredited in the space domain and in the time domain respectively，thirdly a two dimensional FEM code for coupled hydro-mechanical elastic analysis of saturated porous medium is developed tentatively. Then the computations of the effects of rock bolting for an underground opening located under water table，in which the rock mass is assumed to be saturate，are given. For the cases without water and with water (the seepage coefficient K are constants and the functions of the normal stresses respectively)，the elastic analyses are carried out by using the developed FEM code. After investigating the distribution states of the displacements and the pore pressures in the rock mass，it is known：under the condition of groundwater existing，(1) the main action of rock bolting is also limiting the displacements of surrounding rock mass but the action becomes weaker compared with the case without groundwater，(2) rock bolting does not have obvious restraining effect for percolation，(3) the determining patterns of permeability values will greatly influence the distributions of pore pressures in rock mass.

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MODEL EXPERIMENT STUDY ON THE DIFFERENT REINFORCEMENT EFFECTS OF UN-BONDED ANCHOR CABLE AND FULL-LENGTH BONDED ANCHOR CABLE IN ROCK ENGINEERING

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2005, 24 (15): -2689 doi:
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The different reinforcement effects of the two typical anchor cables—un-bonded anchor cable and full-length bonded anchor cable are studied by model experiments of the underground openings and the shear strength of rock mass structural planes. The different reinforcement effects and characteristics of the two typical anchor cables are analyzed and compared by the excavation displacement，failing loads，load-displacement characteristics，strain distribution characteristics of the underground opening wall and the macroscopic damage process of the openings and etc.. By shear tests of reinforced specimen with structural planes and that without structural planes，the different reinforcement effects of the two typical anchor cables on rock mass structural planes are compared. The comparison results of peak shear strength of the reinforced specimen and the variation characteristics of the tensile force of the two typical anchor cables in shearing process are given. The tensile force of the un-bonded anchor cable increases with the shear displacement；however，the tensile force of the full-length bonded anchor cable has almost no change in shearing process. Based on the comprehensive comparison of the reinforcement effects of the two typical anchor cables，some suggestions on the design of reinforcement engineering are put forward.

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FLUID-STRUCTURE INTERACTION MECHANISM OF WATERJET IMPINGING ROCK WITH SATURATED FLUID

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2005, 24 (15): -2697 doi:
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The process of rock breaking under water jets impingement is quite complicated. When high pressure water jets impact saturated rock，three materials interact with each other including jet-pore fluid，jet-rock and pore fluid-rock interactions. A numerical analyzing model of the system is established according to fluid-structure interaction theory. In the model，the standard k-epsilon two equations and control volume method for water jets，and the elastic orthotropic continuum and finite element method for the rock are adopted. Also，a numerical algorithm for the materials is given. The fluid field characteristics and stress distributions in the system are computed under the condition when water jets with 447.2，547.7 and 632.5 m/s respectively impinge the rock using the model and algorithm. The numerical results show that the potent core length is about 10 times the diameter of the nozzle. The radial impact pressure takes on normal distribution，and the impactful range is about 3.5 times of the nozzle diameter as the standoff is about 45 times of the nozzle diameter. When water jet impinges the saturated rock in which fluid flows according to the Darcy¢s law，the pore pressure decreases rapidly as the depth increases under rock surface，and spreads about 7 times of the nozzle diameter along the rock symmetry line. Meanwhile，the maximum principal stress lies under the impact center about 0.4 time of the diameter of the nozzle away. Tension stress causes mainly the rock failure and the crack starts internally and spreads toward the impact surface. The investigation affords a new method for studying the mechanics of rock failure due to water jets impact.

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SIMULATION STUDY OF ROCK FAILURE BASED ON MH-PCA MODEL

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2005, 24 (15): -2704 doi:
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The rock material is heterogeneous from the construction of microscopic view；and the heterogeneous characteristic is one of most important factors that affect the rock failure pattern. In order to analyze this effect，a micro-heterogeneous physical cellular automata model(Mh-PCA model) is introduced according to cellular automata theory from general power view. In this model，the Moore neighbor is adopted and the Weibull distribution is used for simulating the rock heterogeneousness. Using the Mh-PCA model，the evolvements of rock failure are simulated for four kinds of materials with different homogeneous degrees；and the results show that the heterogeneous characteristic has a great effect on the rock failure；the larger the material homogeneous degree is，the fewer crack branches the rock has. All the results are in agreement with experimental results. The physical cellular automata theory can give a new idea for studying the rock failure.

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SPREADING MODEL OF GROUTING IN ROCK MASS FISSURES BASED ON TIME-DEPENDENT BEHAVIOR OF VISCOSITY OF CEMENT-BASED GROUTS

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2005, 24 (15): -2709 doi:
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Experimental results indicate that the viscosity of cement-based grouts is time-dependent，and the law conforms to an exponential function where the shear shows no apparent law，i. e.，，the shear of certain cement-based grout at time t，is nearly equal to its initial value . Based on time-dependent behavior of grouts，a grouting spreading model suitable for rock mass fissures is presented and a programme to predict the grouts spreading with VC++ language is developed. The application of the spreading model in two projects has proved to be successful in practice.

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PROBLEMS OF ENVIRONMENTAL ROCK MECHANICS IN DERIVED CALAMITIES OF RESOURCES EXHAUSTION CITIES

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2005, 24 (15): -2715 doi:
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In the process of resources exhaustion，many kinds of calamities such as ground solid environment calamity，water environment calamity and air environment calamity will derived. In essences，those derived calamities are the problems of environmental rock mechanics. From the aspects of primitive stratum structure，mining causing large area stratum structures weakening，the evolving of calamities，stratum structure nonlinear characteristics，the action of exterior variety and poly-phase environments，the paper analyzes resources exhaustion cities derived calamity characteristics and rock mechanics problems in the evolving process of calamities that include the solid environment calamities，water environment calamities，air environment calamities and the coupled environment calamities.

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NUMERICAL ANALYSIS OF STABILITY USING FINITE DIFFERENCE
METHOD FOR NEW-TYPE SUPPORTING STRUCTURE TUNNEL

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2005, 24 (15): -2718 doi:
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The polypropylene fiber reinforced concrete has higher flexibility and is suitable for supporting structure to adapt the rock mass pressure involved in tunnel rock mass stress relaxation during tunnel construction process. The wet sprayed technology introduced in tunnel engineering can effectively improve the working conditions in tunnel and improve the sprayed concrete quality. The wet-sprayed polypropylene fiber reinforced concrete and anchor system introduced in tunnel supporting structure can achieve good economy effect with better supporting structure compared with the dry-sprayed common concrete. For the safety and stability of tunnel construction process，the numerical analysis of the new-type supporting structure stability and the mechanical characteristics is performed using FLAC (fast Lagrangian analysis of continua). The nonlinear properties of material for rock mass is considered in detail. The distribution of displacement，plastic zone of the rock mass and supporting structure and the axial force distribution of anchor bolt are obtained using the numerical analysis．The results show that the supporting structure can effectively reduce the vault downward displacement and the bottom floor upward displacement enlarging the cavity headroom. The rock mass with the supporting structure works well with each other utilizing the utmost self-bearing capacity of the rock mass.

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PARALLEL PROCESSING OF SEISMIC RESPONSE ANALYSIS
FOR IMMERSED TUNNEL

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2005, 24 (15): -2723 doi:
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Using the high performance computer SGI Onyx3800，this paper introduced finite element method in simulating the seismic response of the immersed tunnel in Shanghai. Consisting the immersed tunnel，soil and river，a large three-dimensional finite element model was finished in the CAE software；and the number of nodes and elements in final finite element model exceeds 1.2 million and 1 million respectively. The seismic response numerical simulation for immersed tunnel is a transient response analysis of large-scale system. Thus，it is impossible to finish this simulation by serial algorithm，serial software and PC. The ultimate calculation adopted explicit dynamic algorithm and parallel domain decomposition method. The recursive coordinate bisection method was used and improved considering the construction feature of immersed tunnel. The result reveals the weak joints in this immersed tunnel under Tangshan seismic waves. It can also provide data and references to the aseismatic design of immersed tunnel and its flexible joints.

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STUDY ON MECHANICAL BEHAVIOUR OF TUNNEL ANCHORAGE SYSTEM FOR SUSPENSION BRIDGE

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2005, 24 (15): -2728 doi:
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Based on numerical simulation results of tunnel anchorage system for suspension bridge，and through validating by similar model field test，the mechanical behavior characteristics，deformation mechanism and stabilization state of rock mass of anchorage system have been researched. The results show that，in main cable tension and operation stage of anchorage，the rock mass clip-holdup effect is to withstand part of the anchorage from rotating up and sliding forward，with the bottom front as fulcrum. Initial prestress，length of free-segment of anchor cable and the load value determine contribution value and action occasion of the anchor cable and tunnel anchorage. Inclination，length，magnification angle of anchorage，interface roughness concentration and bonding capacity，etc. affect the displacement of anchorage and stability of rock mass.

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DOUBLE-SHEAR UNIFIED SOLUTION OF TERZAGHI ULTIMATE
BEARING CAPACITY OF FOUNDATION

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2005, 24 (15): -2736 doi:
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The double-shear unified strength theory is used to derive the formula of the Terzaghi¢s ultimate bearing capacity of foundation. The influence curves of the coefficient b are drawn. The solutions given can be flexibly used to calculate the ultimate capacity of all kinds of different special properties materials foundations. The solutions based on Mohr-Coulomb and double-shear strength theory are all the special cases of its solutions. The unified solutions are greater than that of the Mohr-Coulomb and double-shear strength theory，so the potential strength of materials can be fully applied to the relevant engineering foundation so as to obtain outstanding economical benefit.

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CALCULATION OF THE EXTERNAL LOAD ACTED ON CASING DUE TO SALT FORMATION CREEP WITH FINITE ELEMENT METHOD

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2005, 24 (15): -2741 doi:
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The salt formation is regarded as Maxwell model，and a viscous elastic mechanical model for plane strain features is established. With the analysis and calculation of the external load acted on casing due to salt formation creep under the in-situ stresses，the variation laws of the external load are achieved. The program of finite element method has been established with friendly interface，and the detailed calculation step and formula deduce are presented. Finally，the examples of external load due to the salt creep in the tertiary of Yingmaili oil field have been performed under heterogeneous and homogeneous in-situ stresses. The results achieved in this study may offer reference to the casing design，and provide quantitative and referential evidence for practical engineering cases.

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EXPERIMENTAL STUDY ON COEFFICIENT OF FRICTION BETWEEN A BOX CULVERT AND MIXTURE COMPOSED OF THIXOTROPIC SLURRY AND CLAY OR STEEL PIPE DURING CULVERT BEING
PUSHED BY PIPE-ROOF

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2005, 24 (15): -2746 doi:
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Up to now，the subway crossing project through Hongxu Road is a pipe-roof project with the biggest cross-section box culvert in the world. It is constructed in saturated soft soil stratum in the Beihong Road located in the middle ring-road in Shanghai. Coefficients of friction between the box culvert and mixture composed of thixotropic slurry and clay or steel pipe are of great importance for rationally designing jacks used for pushing the culvert. The coefficients are studied by test. Five kinds of mixtures composed of different proportional thixotropic slurry and clay are used for test. The results show that the coefficients reach maximum when the mixture is completely composed of clay and they reach or approach minimum when the mixture is completely composed of thixotropic slurry. In addition，the coefficients will decrease generally as mass of thixotropic slurry proportion to mass of clay increases.

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CENTRIFUGAL MODELING OF REINFORCED EMBANKMENTS ON SOFT CLAY

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2005, 24 (15): -2751 doi:
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The geosynthetic reinforcing techniques have been widely used nowadays in the design of embankments and foundations on soft clay to maintain stability during or immediately after the construction of the embankment. However，the behaviour of reinforcements on soft clay is far from clear. The objective is to investigate the behaviours of reinforced embankment on soft clay using the technique of centrifugal modelling and to provide a rigorous basis for optimum design of embankments. A series of centrifuge model tests for both unreinforced and reinforced foundations are conducted and behaviours of the subsoil are observed. Based on these tests，the distributions of the horizontal displacement and vertical displacement as well as the dissipation of the excess pore pressure in the clay foundation are obtained. In particular，the effectiveness of the base reinforcement is examined by comparing its behaviour with that of an unreinforced clay foundation. A new technique for measuring the tension induced in the reinforcement was developed and used in centrifuge tests. It is found that a geosynthetic reinforcement is effective in preventing the lateral displacement of the clay foundation，and therefore，may contribute towards the stability of the embankment. In general，the extension of the reinforcement and the settlement of the embankment are consistent，and in the present study，the mobilization of the tension reaches around 52% of the tensile strength.

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STUDY ON STRESS INTENSITY FACTOR AFFECTED BY FRICTION COEFFICIENT BETWEEN SURFACE LAYER AND SUBBASE

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2005, 24 (15): -2757 doi:
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Cracking is a major problem in the asphalt concrete pavement. Based on the linear fracture mechanics，the distribution discipline of the stress intensity factor (SIF) under the changed temperature is studied by the plane strain FEM of ABAQUS software when the surface cracks or the reflective cracks exist in the asphalt pavement on the semi-rigid base. It is obtained that the SIF increases with the length of the surface crack or the reflective crack enlarging in the asphalt pavement. The SIF decreases with the friction coefficient rising when the surface crack tip lies in the surface layer and increases with the friction coefficient rising when the surface crack tip lies in the base. For the asphalt pavement with reflective crack，the SIF decreases with the friction coefficient rising when the reflective crack tip lies in the base. The SIF increases with the friction coefficient rising when the reflective crack tip lies in the base and the reflective crack length is less than a certain value. The SIF decreases with the friction coefficient rising when the surface crack tip lies in the base and the reflective crack length is more than a certain value.

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RESEARCH ON FAILURE MECHANISM AND ULTIMATE LOAD CARRYING CAPACITY OF PRESTRESSED CABLE

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2005, 24 (15): -2765 doi:
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Commonly failure model of prestressed cable is analyzed. Much attention has been paid to geometric form of cable which influences bond strength. By means of theoretical method，the interface behavior between cable and grout is analyzed as well as its failure mechanism. Comparison with practical and laboratory test results has been made. It is shown that theory analysis is in good agreement with experimental results. Furthermore，the ultimate load carrying capacity is established.

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CHARACTERISTICS OF SHEAR STRENGTH AND DEFORMATION OF REINFORCED RED SAND SILTY CLAY WITH GEOSYNTHETICS

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2005, 24 (15): -2770 doi:
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Red sand silty clay is used widely in highway engineering in Hunan Province. The direct shear tests on red sand silty clay with various geosynthetics were carried out to investigate the strength and deformation performances，the influence of parameters such as reinforcement layers and modulus，soil compactness，as well as confining pressures of test. Results show that with increasing compactness，the shear strength of soil increases significantly，but this is mainly caused by cohesive forces，which will disappear gradually with shear displacement increasing，and usually the stress-strain curve of red sand silty clay has a strain-softening phase. Reinforcement improves the stress-strain behaviors of red sand silty clay that both the peak strength and residual strength are increased，but the most important is the amount of reduction of residual strength，and the peak shear strength arrives at a larger shear displacement；as a result，the soil becomes more ductile. Based on the test results，the mechanism of the shear strength of reinforced soil is proposed tentatively；and the role and function of reinforcement in the stress-strain behaviors are also illustrated.

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FIELD SURVEY OF COMPOSITE FOUNDATION WITH RIGID PILES UNDER EMBANKMENT

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2005, 24 (15): -2780 doi:
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When a highway is built on soft clay，vehicles will bounce when they run through a bridge approach because of large settlement difference between a bridge and embankment. Jialichen Bridge uses a composite foundation of rigid piles with different length along embankment to reduce the settlement difference. Embankment weight is a kind of flexible load and prototype observation analysis is reasonable way to study composite foundation under embankment. The prototype observation shows that because settlement of soil is larger than that of piles，an arch effect appears in the embankment so that its weight is gradually transferred from the soil to piles and pile-soil stress ratio increases. Due to the composite foundation，two-thirds of natural foundation settlement is removed. It is more significant that the road surface is basically smooth because of the piles with different length along the embankment. The observation of settlement in different depth shows that larger deformation is developed in the layers nearby the stabilized layer bottom.

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THEORETICAL ANALYSIS AND PRACTICE OF RECTIFYING REINFORCEMENT USING EXPANSIVE METHOD FOR INCLINE BUILDING ON COLLAPSIBLE LOESS

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2005, 24 (15): -2786 doi:
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Incline buildings can be always found in collapsible loess regions because of the improper ground treatment. Differential settlement of the foundation and inclination of the upper-structure bring the building greatly potential danger. Through research and practice of many projects，an expansive rectifying method that the quicklime piles may be used for the rectifying and reinforcement of foundation is proposed on the basis of theoretical analysis and practical experience，and the computational formula for application amount of expanding material is deduced by using pore extruding principle. This method is to drive mixture quicklime piles into the soil under the foundation by applying control monitoring technology and the expansive slaking lime can extrude the loess under the foundation，lift-up the original foundation and increase the compactness of foundation soil，then the purpose of rectifying and reinforcement of foundation is realized. This method was used in many projects and satisfactory results were obtained.

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FOUNDATION REINFORCEMENT AND BUILDING RECTIFICATION OF DEVIATION BY JACK-UP AND PRELOADING UNDERPINNING PILE

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2005, 24 (15): -2795 doi:
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A 3-story brick concrete structural building was added to 7-story in Xi¢an City，Shaanxi Province；and the new-added part is a frame structure. Because two different structural systems are not separated completely and the designer adopted unsuitable ground treatment method，the building became leaning seriously when the major structure was completed. The inclination ratio and settlement rate of building are up to 18.6‰ and 9.15 mm per day，respectively；and the building is bound to collapse. The scheme of rectifying deviation by jack-up and by preloading underpinning pile was employed after investigation for sake of safety. Based on this case，the following aspects are investigated：the formula to determine the numbers of underpinning piles for rectifying leaning building is presented；scheme choice of rectifying deviation，designing method，construction procedure of preloading underpinning pile，jacking monitoring and controlling are introduced in derail；difficult factors and corresponding problems during jacking construction are provided. After 3-day jack-up construction，the inclination ratio of building is steady at 0.53‰ and settlement rate is less than 0.007 7 mm per day and tends to be stable. After five years regular service，it can be concluded that preloading underpinning pile is feasible to reinforce or rectify similar structures and project in loess region.

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张平博士论文摘要

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2005, 24 (15): -2802 doi:
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张平博士论文摘要