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2007, 26 (02): -216 doi:
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2007-02期目录

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FORECAST OF KARST-FRACTURED GROUNDWATER AND DEFECTIVE GEOLOGICAL CONDITIONS

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2007, 26 (02): -217 doi:
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The unknown geological disasters such as water and slurry often gush in karst area during construction of tunnel，which brings momentous disaster and unestimated economic loss to construction safety. The precise and immediate advance forecast to the development of karst is the key problem to be researched and solved currently in tunnel design and construction in the karst areas，which brings important theoretical significance and practical value. A recent development of the forecast and the integration system of the forecast about the karst-fractured groundwater and the defective geological conditions are first introduced in detail. The key issues of karst-fractured groundwater and the defective geological condition in prediction are derived，then the method of forecasting defective geological condition and the karst-fractured groundwater with high pressure and large flow discharge are summarized. The engineering examples such as tunnel seismic prediction(TSP) prospecting karst cave，landsonar prospecting fault，geological radar prospecting underground water and infrared water detecting method prospecting karst-fractured groundwater are introduced emphatically. At last，the effective methods of forecasting all kinds of the defective geological conditions and some study ideas and difficult technology are given；and the next stage of work to be undertaken is discussed deeply. The theory and technology initiative has help and positive guides in the fields of the forecast of the karst-fractured groundwater and the defective geological condition.

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ADVANCES IN TUNNEL BORING MACHINE APPLICATION IN CHINA

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2007, 26 (02): -226 doi:
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Nearly half century has passed since the TBM(tunnel boring machine)was applied in China. Particularly since China carried out reform and open policy，various TBMs have been used in tunnel construction. In the meantime through practice，we obtained a series of experiences and lessons. Since 2002，through the cooperation with manufacturers from the United States，Japan，Germany，France and so on，Chinese machine-building plants have produced many TBMs. Application practices of rock TBMs in China¢s large and medium sized project of hydraulic and hydroelectric engineering，railway，and highway show that the open-type TBM is suitable for good geological conditions of surrounding rocks，while the double shield TBM is suitable for medium geological conditions of surrounding rocks. But where there are a lot of karst caves or high pressure gushing water or dense minor faults or fracture zones in rock masses，the TBM method should be replaced by drilling and blasting because TBMs can not give their advantage of rapid excavation. Shield TBMs have been widely applied in China¢s soft soil tunnels(urban metros and river crossing tunnels). Only in the metro construction of Shanghai，Beijing，and Guangzhou，there have been 72 shields used. Usually，the earth pressure balanced shields are applied to the construction of urban metros because of poorer underground water and lower water pressure in their soil beds，while the slurry shields are applied to the construction of river crossing tunnels because of high water pressure on their excavated sections. Recently，China has begun to undertake the design and construction in using TBMs for foreign countries(for example，Iran and Singapore). Within the coming 10 to 30 years，the construction of 5 undersea tunnels will be taken into account besides the construction of long and deeply buried tunnels in the first and second stages of the West Line of the South-to-North Water Transfer Project in China. And the construction of urban metros，railways，and highways will be accelerated. It can be expected that all of these will certainly make more and more application of TBM in China.

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STUDY ON DEFORMATION MECHANISM AND CONTROL METHOD OF BEDDING ROCK SLOPE ALONG TANGTUN EXPRESSWAY

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2007, 26 (02): -239 doi:
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The engineering geological conditions of a bedding rock slope along Tangtun expressway are investigated systematically；then the types and causes of rock mass structures and the combination between structural planes and slope surface are studied in detail so as to analyze the bedding slope deformation mechanism. A geological model of the bedding rock slope is described by engineering geological profile and partitioned-area map of rock mass structure listed in the paper. The slope evolvement sketch of mechanism from deformation to failure is described；it is shown that the failure process of bedding rock slope，that is，large-scale blocks cut by rock bedding and intense joint band in upper-middle slope slide through bedding weak layer，and rock bends to the surface near slope where cataclastic rock mass exists，which causes the distortion and shearing slide plane in the first-step slope. When the sliding plane cuts through，the slope will fail. The result of FLAC3D numerical modeling indicates that the tension stress distributes along bedding weak layer and in cataclastic rock near slope surface；and potential sliding plane cuts through gradually. The result indicates that bedding weak layer and rock mass structure controls the types of slope deformation；and the present deformation is included in the beginning of the failure type of“creep-fracture and creep-bending”. Slope reinforcement based on the analysis of deformation mechanism focuses on controlling the distortion of cataclastic rock mass and potential shearing exit. Anti-slide pile combined with prestressed anchor and prestressed anchor frames are implemented to reinforce the potential landslide；and drainage works as auxiliary measures are also implemented. The monitored deformation curve indicates that the slope is stable in the rainy season.

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CONSTITUTIVE MODEL OF ROCK JOINTS UNDER COMPRESSION LOADS WITH DIFFERENT FREQUENCIES

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2007, 26 (02): -247 doi:
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Dynamic compression tests of different loading frequencies on artificial joints with different saw-teeth are performed by Instron1342 servo-controlled material testing machine. Based on the analysis of test results，the effect of both the surface topography and loading frequency on the joint closure behavior is discussed. By comparison of the fitting potential of five empirical functions with the closure curves of rock joints under normal loads with different frequencies，it is suggested that the power function is very suitable for expressing the dynamic closure behavior of the joints. By analyzing the quantitative relations between the fitting parameters of power function and strain rates，a new dynamic constitutive model of rock joints is proposed. The test results show that the established model gives reasonable estimations of the deformation behavior of joints under dynamic loads.

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RESEARCH ON METHOD OF NUMERICAL SIMULATION OF PRESTRESSED ANCHOR CABLE IN SLOPE

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2007, 26 (02): -254 doi:
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Prestressed anchor cable have been widely used as a main reinforcement method in geotechnical engineering，and its effective reinforcement capabilities have been validated by many project cases. However，for the existing method of numerical simulation of prestressed anchor cable in slope has some disadvantages，the result of numerical simulation in FEM isn¢t in accord with practical one. This paper tries to discuss these disadvantages about the existing method of numerical simulation of prestressed anchor cable in slope and put forward a series of measures. Then，the authors suggest a new method of numerical simulation of prestressed anchor cable in slope which will simulate the whole process in construction and operation period. At last，the abutment slope in Jinping Hydroelectrical Project illustrates the difference between the existing method and the proposed method.

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RECURRENCE MATRIX OF PERMEABLE PROBABILITY IN PERCOLATION MODEL FOR FRACTURED ROCK MASS

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2007, 26 (02): -262 doi:
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The 2D site percolation model is used for characterizing the permeability problem of fractured rock，in which the rock mass is divided into a network of many elements，each element assigned a definite permeable probability. An analytical method is proposed for calculating the permeable probability of fractured rock mass. The concept of recurrence matrix of permeable probability is introduced；and the recurrence matrices of permeable probability are derived for the networks of 3×n and 4×n elements，with which the permeable probabilities of arbitrary columns of elements can be determined. Based on the recurrence matrix of permeable probability，the analytical formulas of permeable probability are derived for networks of 3×3 and 4×4 elements. By using the renormalization group method，the critical permeable probabilities are calculated for networks of 2×2，3×3 and 4×4 elements respectively in comparison with the results obtained by the Monte Carlo method. Finally，the errors inherently in the renormalization group method are investigated.

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STATE OF THE ART OF INRUSH MODELS IN ROCK MASS FAILURE AND DEVELOPING TREND FOR PREDICTION AND FORECAST OF GROUNDWATER INRUSH

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2007, 26 (02): -268 doi:
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Based on extensive literature review，the state of the art of coupled hydromechanical models and in-situ monitoring for groundwater inrush predictions are summarized in detail，based on which，it is proposed that the key issues for describing the seepage characteristics during groundwater inrush are to calibrate the equations for damage-induced evolution of permeability and of effective stress. Depending on in-situ experiments and numerical simulations，a new academic idea，i.e.“the rock microseismicity induced by mining processes and water pressure disturbance is in essence the index of groundwater inrush”，is put forward. Based on case studies，coupled hydro-mechanical theory，high-performance computing technology and microseismic monitoring. The authors propose that the tendency for analyzing and predicting the groundwater inrush is to synthetically inverse the inrush pathway formation，strata microseismic precursor and high performance computing results. And relying on the microseismic monitoring events，the groundwater inrush models are calibrated，which could be used to clarify the precursory characteristics and to locate the inrush pathway. This study will lay theoretical basis for establishing the models to predict the groundwater inrush in underground mining.

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COMPARISON OF SLIDING CRACK MODELS FOR ROCK-LIKE MATERIALS

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2007, 26 (02): -278 doi:
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The sliding crack model has been widely applied in the damage and fracture analysis of the rock-like materials. Considering systematically the influence of the main crack direction，winged crack direction，confining pressure and the dimensionless winged crack length，six typical calculating models for I-model stress intensity factors are compared. What¢s more，for the case where the winged cracks are aligned in the direction of the principal compressive stress，a finite element analysis is carried out. Comparing the results of finite element method and those of six theoretical models，it is concluded that three models among are able to get perfect results，and one model is useable only under uniaxial loading，while the results of the other two models are obviously different from FEM results. These conclusions would be useful for the further study of damage and fracture of the rock-like materials.

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PREDICTION RATE OF GIS-BASED MODELS FOR PREDICTING LANDSLIDES AND ITS APPLICATIONS

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2007, 26 (02): -285 doi:
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Selection of models for predicting landslides directly influences the accuracy of landslide prediction and is the key factor in landslide prediction. By using the geo-spatial data about landslides and related resulting factors in Alpago，Italy，the roles and applications of prediction rate of models for predicting landslides are discussed. Four models are used as examples including fuzzy gamma model(FGM)，fuzzy algebraic product model(FAPM)，fuzzy algebraic sum model(FASM) and fuzzy minimum model(FMM). Prediction rate is the cumulative distribution function of the area percentage of the landslides not used to construct a model with respect to the classes in the prediction map generated. By using the geographic information system(GIS)，the prediction rate of a model can be calculated with the prediction map generated by the model and the landslide distribution data not used to construct the model. Based on the calculated prediction rates，the prediction abilities of the four models are compared and evaluated. The results show that the prediction rate of a model for predicting landslides is an indicator of the model characteristics；and that under the condition of defined input layers and specified landslides，the prediction rates of different models can be used as quantitative criteria for comparing，evaluating the models and for selecting the best one.

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STOCHASTIC ANALYSIS METHOD ON SAFETY OF SURROUNDING ROCK MASS BASED ON YIELDING APPROACH INDEX

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2007, 26 (02): -292 doi:
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A new stochastic analysis method on safety of heterogeneous surrounding rock mass is developed. In order to describe the intrinsic heterogeneity of strength of the same rock，the safety parameter ω，which is the phase complementary parameter of YAI(yielding approach index) proposed in the previous studies by the authors，is firstly supposed to be a stochastic variable in this paper. And by analyzing the triaxial test data，the strength parameters of five types of rock samples are recognized and the corresponding ω is calculated. It can be found that ω is correspondent to the Weibull¢s distribution function which is proved to be appropriate through the laboratory test data. Secondly，the stochastic analysis method is proposed to simulate the random loose zone. And the random yield behavior of rock mass is reflected in the results. In fact，rock mass in engineering behaves more complex than rock samples in laboratory do. So the parameters of Weibull¢s function and the mechanical parameters of rock mass should be recognized through the measured depth of loose zone in-situ. Therefore，a GA-NN(genetic arithmetic neural network) method is employed to perform the back analysis of these parameters. Finally，a case is analyzed by applying the proposed stochastic analysis method above to the analysis of the safety of the heterogeneous rock mass. The results show its simplicity and practicability，and agree perfectly with those measured in-situ，and can supply as important references for the underground engineering.

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MESOSTRUCTURAL CHARACTER AND NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF SOIL-ROCK MIXTURES

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2007, 26 (02): -300 doi:
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Soil-rock mixture is a kind of inhomogeneous material；for the difficulty of in-situ sampling and the underdevelopment of large-scale laboratory soil test，at present the study of the soil-rock mixture¢s mechanical properties is still at initial stage. With the quick development of digital image processing method，digital image processing has been successfully used in many kinds of fields. Based on the digital image processing，the microstructural model of soil-rock mixture by taking into account the actual material inhomogeneity is constructed. The structural character of the distribution of blocks is studied statistically；and it is shown that the confusion is only the external performance of the soil-rock mixtures. In fact，soil-rock mixtures have a good character of self-comparability in statistics. Using geometry transformation，the model of soil-rock mixtures under dual digital image has been translated into a document format which can be received by finite element software. By this step，the numerical simulation of actual microstructures of soil-rock mixture is carried out. The numerical simulation of the large-scale direct shear test indicates that the blocks obviously influence the stress field of soil-rock mixtures，and then influence the deformation and fracture type. Three kinds of possible failure propagation routes in soil-rock mixtures are put forward.

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STUDY ON HYPOPLASTIC CONSTITUTIVE MODELING OF ROCKFILL
AND ITS APPLICATION

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2007, 26 (02): -312 doi:
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Hypoplastic constitutive theory，which was originated from the middle and late stage of the 20th century，is a new type of soil constitutive theory based on rational mechanics. Hypoplastic theory can reflect inelasticity，nonlinearity，dilatancy and other main mechanical properties of granular material. The origin and development，general representation of hypoplastic constitutive model are introduced；and mechanical and mathematical analysis is made. Besides，the modeling thought of recently updated hypoplastic models is briefly introduced based on the study of the relation between void ratio and mean pressure and the relation between void ratio and volumetric strain of granular soil. Combining with the analysis of main mechanical properties of rockfill，the Gudehus-Bauer hypoplastic model which can reflect the latest international hypoplastic research level is modified properly and applied to constitutive modeling of rockfill. Finally，the new modified model is used in the hypoplastic numerical analysis of deformation and stress of a typical concrete face rockfill dam. Theoretical analysis and engineering application show that the new updated model can reflect inelasticity，nonlinearity，dilatancy and other main mechanical behaviors of rockfill and has the advantage of wide adaptability of constitutive parameters.

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NUMERICAL SIMULATION OF ORTHOTROPIC ANISOTROPIC DAMAGE CONSIDERING ROCK-WATER INTERACTION

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2007, 26 (02): -323 doi:
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An orthotropic anisotropic elastic damage model has been proposed，and the elastic deformation，damage deformation and other irreversible deformation can be identified respectively. A second rank damage tensor is used to characterize the induced damage with damage evolution being related to the propagation criteria of microcracks. A specific form of the Gibbs free energy function is used to obtain the effective elastic stiffness，and the limited scopes of relative anisotropic damage parameters are suggested based on the energy principle. A method for determining of all parameters of the anisotropic damage model is proposed by virtue of conventional triaxial test. The mechanical behaviors of different loading paths are described，such as proportional loading，lateral unloading；while the comparison between test data and numerical simulations shows an overall good agreement. Then，the anisotropic damage model is extended to describe the hydro-mechanical behaviors to simulate the coupled hydro-mechanical responses in different loading paths. The numerical results show that the proposed and extended model is suited to describe the main features of hydro-mechanical behaviors of rock.

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PHYSICAL MODEL TESTS ON INFLUENCE OF PIPE DRAINAGE SYSTEM ON SLOPE RESIDUAL DOWNSLIDE THRUST

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2007, 26 (02): -331 doi:
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The physical model tests were performed to study the influence of pipe drainage system on soil permeability，groundwater level and slope residual downslide thrust. The test results verify that groundwater pipe drainage system in pebbly-clay slope can markedly improve the soil permeability，drawdown the groundwater level，therefore decrease the slope residual downslide thrust and increase the slope stability. It is pointed out that underground drainage engineering should be the main measure in pebbly-clay landslide control.

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STUDY ON SAFETY IMPACT ASSESSMENT AND REINFORCEMENT MEASURES OF COAL MINING UNDER IMPORTANT HYDRAULIC ENGINEERING

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2007, 26 (02): -338 doi:
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Exploitation of mine resources will exert potential threats upon the safe operation of important hydraulic engineering projects in China. Based on practical projects and field monitoring curves of coal mining near an ore district，numerical simulation method is employed for the back analysis of mechanical parameters of rocks and soils in Yangcun Ore District. The impacts on the security of Xifeihe River left embankment under coal mining are evaluated with elastoplastic model，two-exponent rheological model and probability integral method. Based on current national regulations or codes and over 40-year practical mine experiences in China，the controlling indices and the reduction factor for deformation of Xifei River left embankment by coal mining are primarily presented. On the basis of above results，the proposed scheme 3(600 m far from embankment) is recommended for a formal mining scheme；and corresponding comprehensive protection measures are presented. It can offer a scientific basis and can be served as a reference to the similar projects，such as mining at Nansi Lake and mining at the major channels of Middle Route of South-to-North Water Transfer Project.

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NUMERICAL ANALYSIS OF FORMING MECHANISM OF CRACK IN STANDARDIZATION DIKE ON YELLOW RIVER IN DONGMING OF SHANDONG PROVINCE

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2007, 26 (02): -347 doi:
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In the course of building the downstream standardization dike in Yellow River，the method of reinforcing dike with silt was adopted. By far，longitudinal cracks appear in the first stage project in Dongming of Shandong Province，which would endanger the safety of dike. It has huge complex impacts on dike body to reinforce dike with silt，and little study is carried out. There are no quantitative results about the forming cause of crack，so it is very difficult to prevent and deal with radically. By experiment on typical dike section，and theories and methods such as unsaturated seepage，liquid-solid coupling，soak deformation，finite element analysis and so on used to simulate the process of construction，the forming mechanism is analyzed and the main factors are discussed by analyzing several special working conditions. Study shows that the cracking course of dike body can be reflected by simulation；and the results are in accord with the fact. The main factors are reinforcing dike with silt，construction in high speed，soak deformation，poor drainage，stacking load at the tip of dike，impact of vehicle and so on. The results can provide references to building the standardization dike and similar projects.

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RESEARCH ON HYDRO-THERMAL COUPLING NUMERICAL SIMULATION WITH ARTIFICIAL MULTI-FREEZING-TUBE CYCLES

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2007, 26 (02): -355 doi:
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During the coupling analysis of moisture field and temperature field in freezing soil by using artificial multi-freezing-tube cycles，a lot of factors should be considered，including multi-fields and nonlinear problems，etc.. Their relations are complicated. The model tests of freezing process with multi-freezing-tube cycles are conducted. The regulation of variation of temperature field and moisture field with freezing time are obtained. It is proved that the temperature is the source of variation of moisture field；and the hydro-thermal coupling dominant equation is proposed. The finite element method is used to carry out hydro-thermal coupling movement with the hydro-thermal coupling parameters being solved simultaneously. It can simulate the characters of temperature forming and development，freezing moisture field transferring，as well as the coupling relation of the two fields. The results of numerical simulations and model tests have good coincidence. The hydro-thermal coupling analysis in this study has important reference to designing and optimizing freezing wall. The results have promotion role for both technological progress and theoretical development of shaft sinking by artificial freezing process with multi-freezing-tube-cycles in thick overburden.

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3D DYNAMIC SIMULATION AND ANALYSIS OF SLOPE
INSTABILITY OF RESERVOIR BANKS

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2007, 26 (02): -360 doi:
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The slope movement is a complex and dynamic process，especially the slope of the reservoir banks. During the moving process of reservoir slope，huge surge usually appears with it and has a great effect on it，so it is more difficult to describe the moving process of this kind of slope movement numerically than the others. Based on the rebuilt 3D geological model of slope of the reservoir banks，the mechanism of instability is analyzed by using 3D limit equilibrium method firstly，which provides an environmental background for the visual simulation. Then，in the case that the reservoir slope may be instable，the flow chart for digital and visual dynamic simulation of its movement is presented，according to the special features of two stages of the reservoir slope motion process，i. e. movement on ground and movement below water level. Finally，the whole process of reservoir slope movement is unified and its 3D visual dynamic expression is realized. The outcome of the application to an example gives a visual description of the slope motion process and the surge undulation at the same time，which demonstrates the feasibility and practicability of this method. Thereby it supplies a more convenient and visual analysis means for the research of slope motion process.

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COUPLED MICROMECHANICAL MODEL FOR ANISOTROPIC DAMAGE AND PERMEABILITY VARIATION IN BRITTLE ROCKS

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2007, 26 (02): -368 doi:
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A coupled model for anisotropic damage and permeability variation by using a micromechanical approach is presented. The damage state is represented by oriented distribution of microcracks，damage evolution in rock is defined from a crack propagation criterion；and the free entropy and constitutive law of cracked rock are obtained by using micromechanical method. It is assumed that the cracks exhibit normal aperture which is coupled with the crack growth due to asperities of crack faces. By using Darcy¢s law for macroscopic fluid flow and assuming laminar flow in microcracks，the overall permeability of RVE is obtained by a volume averaging procedure taking into account crack aperture in each orientation. An analyzing case shows that the result by the model perfectly agrees with experimental one.

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STABILITY ANALYSIS OF REINFORCED SLOPE LOADED
BY A STRIP FOOTING

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2007, 26 (02): -374 doi:
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The paper describes a numerical model that is developed to simulate and analyze the response of three instrumented，full-scale，reinforced and un-reinforced slopes under a strip footing. The fast Lagrangian analysis of continua(FLAC) program based on strength reduction technique is used in numerical analysis. The displacement response，velocity vectors of nodal displacements，plasticity indicators and shear strain rate under strip footing are calculated. So the ultimate bearing capacities and the failure mechanism of two-part wedge for slopes are gained，which are in better agreement with test results. It is shown that the model is satisfactory. On the basis of these，the main factors influencing on slope stability are analyzed. Numerical results indicate：the bearing capacity and stability of reinforced slopes are obviously improved，and increase along with the add of the numbers of layers，stiffness and strength of geogrids. The larger the magnitude of strip footing is，or the farther away from the crest of slopes，the lower the stability of slopes is. The greater the soil strength is，the higher the stability of slopes is；but the friction of soils is more sensitive to safety factor than cohesion of soils. Besides，the depth of topmost geogrid to the width of strip footing is also greatly correlative to the safety factor，and the best ratio changes with the layers of geogrids.

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THEORY ON LONGITUDINAL VIBRATION OF PILE IN VISCOUS DAMPING SOIL LAYER CONSIDERING THREE-DIMENSIONAL WAVE EFFECT AND ITS APPLICATIONS

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2007, 26 (02): -381 doi:
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Modeling soil as a 3D axisymmetric continuum and taking its 3D wave effect into account，the interaction between soil layer and pile with viscoelastic bottom boundary undergoing arbitrary vertical load is theoretically investigated. The investigation will be of significance for dynamic test of pile. The pile is assumed to be vertical，elastic and of uniform cross-section，and the soil is considered as a linear viscoelastic layer with viscous damping. With Laplace transforms，the question can be solved in Laplace domain. With the aid of two potentials，the displacement of soil is decomposed and the dynamic equilibrium equation of soil layer is uncoupled and solved first. Thus the vibration modes of the soil layer are obtained to analyze the pile response. By considering the interaction between the soil layer and the pile with boundary condition of continuity of displacement and equilibrium of force at their interface，the dynamic equilibrium equation of pile is solved and an analytical solution for the displacement function in Laplace domain is yielded，so are the corresponding analytical solutions for the mobility at the level of the pile head in frequency domain. With the convolution theorem and inverse Fourier transform，a semi-analytical solution of velocity response in time-domain subjected to a semi-sine exciting force is derived. Based on the solutions proposed herein，a parametric study of the effect of some governing dimensionless parameters on mobility curves and velocity reflection wave curves is conducted to illustrate the main features of longitudinal vibration of pile.

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STUDY ON CREEP PROPERTIES AND NONLINEAR CREEP MODEL
OF SOFT ROCK

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2007, 26 (02): -391 doi:
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Based on the creep curves of soft rock under uniaxial compression，a damage variable and a hardening function are introduced into creep model to express the nonlinear creep behavior of soft rock. A new nonlinear model for axial and lateral creep is established for soft rock. The typical creep curve can be divided into three phases，which are decelerating creep phase，even creep phase and accelerating one. The hardening of viscosity coefficient is the main cause of the decelerating phase of creep；and the accelerating phase is mainly due to the damage of the elastic modulus. The damage mechanism and the hardening one keep its balance in the even creep phase. It is unreasonable to describe and explain the three-phase creep by using the nonlinear viscosity coefficient only or the damage of elastic modulus. The three-phase creep course is the results of the competition between damage and hardening. With the creep development of soft rock，rock microstructure changes influence upon the mechanical behavior. Those changes are explained by nonlinear damage and hardening variables. A nonlinear creep model is constructed which can describe the three-phase axial creep of soft rock. Furthermore，the creep Poisson¢s ratio is introduced into creep model to express the lateral creep behavior of soft rock；and the energy damage variable is used to describe the anisotropic elastic damage. The results of the model and tests for mudstone and red sandstone are perfectly fitted.

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APPLICATION OF HIGH FREQUENCY ULTRASONIC GUIDED WAVES TO INSPECTION OF FULL-LENGTH-BONDING BOLT

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2007, 26 (02): -397 doi:
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Propagation characteristics of high frequency longitudinal axisymmetric modes in full-length-bonding bolt are studied. For the same mode in bolt，its attenuation and velocity vary greatly with frequency range. In theory，there is high order longitudinal mode above 1 MHz whose axial displacement concentrates in the middle of bolt. Its attenuation is the smallest，and its energy velocity is the fastest in all modes at the special high frequency. This indicates that the high order low loss longitudinal mode can be used to inspect full-length-bonding bolt. At the same time，the experiments about diameter 22 mm，1m length bolt without defect embedded in grout detected using ultrasonic guided wave are carried out. The scope of inspection frequency is between 1.13 MHz and 2.85 MHz. The velocity and amplitude curves of first end reflection with frequency are made. The experiment curves are consistent with those dispersion curves of theory. Besides，the experiment that the bolt with one defect embedded in grout detected by guided waves also is carried out. This indicates that ultrasonic guided waves can be used to inspect the length of bolt and confirm the location of defect. Finally，site inspection for diameter 18 mm，2 m length bolt is performed. The inspection results show that the guided waves technology is available for the nondestructive testing of full-length-bonding bolts.

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ANALYSIS OF TIME-SPACE EFFECTS OF CONSTRUCTION BEHAVIOR OF DEEP SOFT ROCK TUNNEL

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2007, 26 (02): -404 doi:
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With the rapid development of transportation，it is inevitable to excavate tunnel in the deep rock mass，and the problems of special engineering geology in deep rock mass will be much more distinct. The 3D nonlinear viscoelasticity numerical simulation and analysis are conducted on time-space effect of mechanical behaviors and deformation characteristics of deep soft rock mass during the tunnel construction；and the calculation results are compared with the field data. Considering rheological effect and time-space effect of deep soft rock tunnel，the results of show that the effect of excavation face is primary in the advancing face zone and the stress of surrounding rocks gradually releases from the excavation face. Rheological effect plays a key role out of the influence range of the spatial effect of excavation face. According to the characteristics of deep soft rock tunnel，support structure should be established as soon as possible in order to ameliorate the stress in surrounding rock circle，to reduce disturbance and to improve the self-bearing capability of the surrounding rock. Because of the distinct rheological property of soft and weak rocks，the secondary support structure must be established in time to bear the rheological pressure. Thus，the large displacement could be restricted by the secondary support structure. The present research enriches the theory of construction mechanics of underground structures and has wide application prospects in engineering.

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EXPERIMENTAL STUDY ON COEFFICIENT OF SENSITIVENESS BETWEEN PERCOLATION RATE AND EFFECTIVE PRESSURE FOR LOW PERMEABILITY ROCK

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2007, 26 (02): -410 doi:
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There exists distinct fluid-solid coupling effect during seepage in low permeability rock. Experiments upon sandstone from Changqing oil field are performed with FDES–641 triaxial system to investigate the laws between the permeability of rock and the effective pressure. It is proved by experiments that the permeability of rock will drop regularly along with the increasing of the effective pressure. With the increasing of effective pressure，the permeability of rock decreases. The variation relation between them can be described by quadratic equation. When plot curve in the reference frame with X-axis to be the effective pressure and Y-axis the permeability of rock，an inflexion of the curve exists. Before reaching the inflexion，the permeability of rock will drop more quickly but after the inflexion such dropping will become more gentle. The location of inflexion in curve will vary for different rocks. The coupling mechanism of seepage in rock mass has not been completely made clear so far；and the coupling factors affecting the permeability of rock are actually too complex to describe one by one. The coefficient of sensitiveness between the permeability of rock and the effective pressure is defined accordingly as to generalize these factors. Such coefficient can evaluate the changing trend of the permeability of rock related to the effective pressure. The higher the coefficient is，the bigger amount the permeability of rock will change along with the effective pressure. By the way the effort to determine the value of permeability can shift to find out the coefficient of sensitiveness. According to the numerical fitting result of experiments，the relation between the coefficient of sensitiveness and the effective pressure can be described by exponential function. The expression between the permeability of rock and the effective pressure is deduced based on the conception of coefficient of sensitiveness.

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MODEL TEST STUDY ON FROST-HEAVING FORCE IN RETAINING STRUCTURE OF ROW-PILES AND FROZEN SOIL WALL OF SUPER DEEP FOUNDATION PIT

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2007, 26 (02): -415 doi:
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The retaining structure of row-piles and frozen soil wall will be adopted in the south anchor deep foundation pit of south branch suspension cable of Runyang Bridge，which is 29 m deep and 69 m× 51m in plan. To solve the problem of determining the frost-heaving force in design，model test is made to study the frost-heaving force in the retaining structure of row-piles and frozen soil wall of super deep foundation pit. First，the similarity criterion of the model test was deduced according to similarity theory. Then the design and model construction are carried out. Finally，the horizontal frost-heaving stress against row-piles without pressure relief holes is 0.238 MPa，which is obtained by test firstly. And the average horizontal frost-heaving stress against row-piles with pressure relief holes is 0.133 MPa. The horizontal frost-heaving force is attenuated in the process of excavation with the maximum attenuation rate being 40 percent. The research results can provide designing basis for this kind of retaining structure.

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APPLICATION ANALYSIS OF EARTH PRESSURE COMPUTATION FORMULAE IN LARGE SQUAT SILOS

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2007, 26 (02): -421 doi:
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In order to reasonably compute the bulk-solid lateral pressure，the pressures predicted by Rankine and Coulomb formulae are compared with those by experiments，the formulae of the Appendix C of Code for Design of Reinforced Concrete Silos(GB50077–2003) are analyzed and verified；and a formula of lateral pressure acting on the wall of large squat silos is obtained based on the static equilibrium method. The results indicate that the pressures predicted by Rankine and Coulomb formulae are larger than the actual values；the formulae of the current code Appendix C need to be supplemented in application process；and the formula based on the static equilibrium method is succinct and the predicted pressures agree well with the actual values and the finite element method results.

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TEST RESEARCH ON RELATIVITY BETWEEN DYNAMIC AND
STATIC ELASTIC MODULUS OF CLAY

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2007, 26 (02): -427 doi:
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According to the engineering and dynamic characteristics of certain clay，the relationship between dynamic and static elastic modulus of the clay with different water contents has been studied by standard compaction test，compression test，wave velocity measurement and analysis of dynamic and static elastic parameters of seven clay samples. The ratio of water content to density is used as a variable to study dynamic，static elastic parameters. The transformations of dynamic，static elastic modulus and dynamic，static Poisson¢s ratios have been constructed. The test results indicate that：(1) the relationship between dynamic or static elastic modulus and water content is a cubic curve，and so are the dynamic and static Poisson¢s ratios. The dynamic and static moduli decrease while static and dynamic Poisson¢s ratios firstly decease and then increase when water content increases；(2) the cubic curve is also suitable for the relationship between the ratio of dynamic to static elastic modulus and the ratio of water content to density. The ratio of dynamic to static elastic modulus increases while the ratio of the static to dynamic Poisson¢s ratio firstly deceases and then increases when the ratio of water content to density increases；(3) the dynamic elastic modulus is larger than the static one；but the dynamic Poisson¢s ratio is smaller than the static Poisson¢s ratio；(4) the ratio of water content to density as transformation variable between dynamic and static elastic parameters has high fitting accuracy；(5) the static and dynamic Poisson¢s ratios vary smaller than the elastic modulus when the water content changes and the similar results have been gotten when the ratio of the water content to density changes. This research presents the experimental basis for the application of dynamic and static elastic moduli of clay in engineering and also provides a new method to study the relationship between the dynamic and the static elastic modulus of clay.

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本刊2006年增刊2被EI收录论文(141篇，收录率为100%)题录

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2007, 26 (02): -433 doi:
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本刊2006年增刊2被EI收录论文(141篇，收录率为100%)题录

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2007, 26 (02): -434 doi:
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