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2003, 22 (09): -0 doi:
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CONSTITUTIVE RELATION OF ELASTOVISCOPLASTIC POROUS MEDIA SUBJECTED TO SHOCK
——PART I：STATE EQUATION

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2003, 22 (09): -1405 doi:
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The process of deformation and fracture of deformable solid media subjected to shock is accompanied by many irreversible dissipative mechanical，physical and chemical processes，and the constitutive equations of solid subjected to shock should express these irreversible features. The mechanical behaviors of elastoviscoplastic porous media subjected to hydrostatic shock are studied here in the framework of irreversible thermodynamics of elastoviscoplastic media. The corresponding constitutive equations are expressed by Helmholtz free energy of Debye form，as it is more rational for solid. The influence of porosity on the mechanical behaviors of elastoviscoplastic porous media subjected to hydrostatic shock is remarkable，and here it is considered by means of effective strain method. The evolution equation of porosity is also obtained on this basis. The constitutive equations presented here are relatively simple，and their physical meaning is clear，corresponding to irreversible thermodynamics. In order to validate the proposed constitutive relations，a numerical example is given，and the agreement is good with the existing results.

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MECHANISM ANALYSIS AND TESTING STUDY ON
DAMAGE AND FRACTURE OF BRITTLE ROCK

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2003, 22 (09): -1411 doi:
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[PDF 630 KB] (1223)

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In order to probe into the damage and degradation influence of seepage pressure on brittle rock and the seepage characteristic law during the deformation of brittle rock，the brittle rock specimens collected from the Three Gorges shiplock slope and the site of Wanjazhai hydraulic power station are tested antithesesly under different stress levels. Then，the microtest，SEM，is carried out to study the failure surface of brittle rock. The testing result indicates that the seepage character of brittle rock is of district difference before and after failure. So，it is concluded that the seepage pressure makes the effect strongly on the fracture and dilatation of rock. Based on the theoretical analysis and testing study on the damage and fracture of brittle rock，the mechanism of crack initiation and micro failure of rock under seepage pressure is gotten clearly. And，reliable testing basis is offered to analysis on the weathered rock instability of high slope under the condition of water pressure suddenly rising or falling during the oozing of rainstorm.

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EFFECT OF DILATANCY ON ROCK FRACTURE PARAMETERS

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2003, 22 (09): -1417 doi:
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At the tip end of fracture，there is very high stress and dilatancy occurs during hydraulic fracturing. Although the fact is well known in petroleum engineering，the effect of dilatancy is not clear on the rock fracture parameters. Based on the knowledge of mechanism of compression-induced dilatancy，the rock porosity permeability(K)，elastic modulus(E)，fracture length(Xf)，width(wwn) are changed during hydraulic fracturing. The rock mechanics related problems are discussed in detail.

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MEASUREMENT OF CRACK WIDTH IN ROCK INTERIOR
BASED ON X-RAY CT

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2003, 22 (09): -1421 doi:
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The deformation，propagation and expansion of crack in rock interior are the main mechanical process when the rock sample comes to its crack evolution stage. It is the subject of this paper how to detect the crack width through X-ray method. The relation between rock density damage and its volumetric strain is analyzed based on the meso-mechanism of rock deformation and rupture. For brittle rock，its volumetric strain has a unique quantitative relation with its density damage. Based on the increment formula of density damage，the volumetric strain formula is derived for rock. The universal calculation formula of crack width in rock interior is derived based on the volumetric strain formula. The formula is tested and compared with relative formula. The same results are obtained from the two different formulas. Two crack widths in rock interior under different stresses are calculated. As a result the problem how to measure a real-time crack width in rock interior is solved theoretically. The crack width of sandstone is no more than the order of magnitude of 10-1mm. It is verified that the actual crack width is not the same as the crack width in its CT image. Before the maximum strength，the crack width of sandstone has a stable expansion process. When the longitudinal and lateral deformation of rock sample are considered，this result can be verified indirectly.

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TEXTING STUDY ON MOVEMENT PROCESS OF ROCK PIECES IN CUT CAVITY BY X–RAY PHOTOGRAPH

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2003, 22 (09): -1426 doi:
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The cut is major factor to affect tunnel blast. The movement process of rock pieces in cut cavity is a theory base for cut blast mechanism and the parameter design. Rocks are non-transparency and brittle. It is difficult to simulate the movement of rock pieces in cut cavity by math and physics. X-ray is of strong penetration ability. It is possible to use high-speed X-ray photograph to survey insitaneous change process in rock body. The mechanism of parallel cut blast with empty holes is studied with model testing and high-speed X-ray photograph. The movement situation of rock pieces in cut cavity is gained. At the same time the study develops a new way to survey the insitaneous change process in rock body and the other non-transparency brittle medium.

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DEVELOPMENT AND APPLICATION OF NEW TECHNOLOGY FOR 3D GEO-MECHANICS MODEL TEST OF LARGE UNDERGROUND HOUSES

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2003, 22 (09): -1430 doi:
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[PDF 388 KB] (1291)

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Several newly developed techniques and methods for 3 dimensional geo-mechanics model test are introduced，such as new model material NIOS with high density and low cost，so-called discretized finite principal stress surface loading and monitoring system for the generation of the modeled initial stress field of the test，the special technique and apparatuses for modeling the excavation of houses located deep inside the model material，inner peep technology and so on. By adopting those new techniques and methods mentioned above，a very large 3D model test with high comparability for a newly designed underground powerhouse has been fulfilled. The excavation sequence and the supporting reinforcements were also modeled in the test. The model test was successful and the results were fairly satisfactory. Those techniques and methods can be used for other large geo-mechanics model test.

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FAILURE ANALYSIS OF INTERMITTENT JOINTED ROCKS
UNDER COMPRESSION-SHEAR STRESS

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2003, 22 (09): -1437 doi:
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The mechanical behavior of jointed rockmass is mainly controlled by joints. The interaction between joints and the coalescence of joints are important problem for geotechnical engineering. The coalescence of two collinear joints and a periodic row of collinear joints are investigated by using Dugdale-Barenblatt model，and the high level of compression-shear stress and interaction between joints are considered. The mechanical conditions of joint propagation are determined by stress intensity factor and the length of damage and strain localization zone. Experimental validations are given to illustrate the applicability of the proposed model. The conclusions are of important significance for rockmass engineering.

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APPLICATION OF OPTIMIZING METHODS IN CALCULATING PERSISTENCE RATIO AND COMPREHENSIVE SHEAR STRENGTH OF JOINTED ROCK MASS

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2003, 22 (09): -1441 doi:
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The approaches of determining the joint persistence ratio of rock mass by dynamic programming and genetic algorithm methods are described based on a simple test example. In a simulated joint map，both methods are able to find the combinations of joint and rock bridge associated with the least comprehensive shear force. It is found that the two methods gave virtually the same results. The influence of two different shearing terminal conditions is investigated on the calculation results. The joint persistence ratio obtained by fixing both ends of shear path is smaller than that without fixed ends，and the comprehensive shear strength with both fixed ends of shear path is larger than that without fixed ends.

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NEW NEURAL NETWORK FOR CONSTITU- TIVE MODELING

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2003, 22 (09): -1448 doi:
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[PDF 93 KB] (738)

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In this paper，a new neural network is developed to connect FE analysis with the feed-forward neural network. With this new neural network，the constitutive model of material may be determined from the information of nodal’s force and displacement. In this methodology，the stage which takes long time to obtain stress and strain by FE analysis is prevented.

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NEURAL NETWORK MODEL OF THE CONSTITUTIVE RELATIONSHIP OF CLAY UNDER MULTIPLE STRESS PATHS

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2003, 22 (09): -1454 doi:
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[PDF 189 KB] (990)

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Based on the model parameter identification theory in inverse problem，a neural network model for constitutive law of clay under multiple stress paths is set up through artificial neural network. This method in modeling the constitutive relation for soil is superior to the traditional one. Not only almost all information involved in test data can be used，but also the influence of stress paths on the constitutive law for clay can be quantitatively reflected. This is significant for computer simulation of geotechnical engineering.

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GENETIC ALGORITHM FOR PARAMETER INVERSION
OF SATURATED POROUS MEDIA

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2003, 22 (09): -1458 doi:
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[PDF 196 KB] (960)

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Fluid saturated porous medium(FSPM) is a two-phase medium composed of solid and fluid. Contrasted with classical single-phase elastic media，the two-phase medium is more close to actual earth stratum，hence，FSPM model is widely used in various engineering，such as the geophysical prospecting，earthquake engineering，and rock and soil dynamics，etc.
According to the principle that the computed response and measured response should be fitted，the parameter inversion problem of porous media is reduced to optimal problem of non-linear multimode function. The traditional optimal methods，such as gradient method，perturbation method，or time-convolution regularization iterative method，are based on Newton iterative method with local convergence. In order to overcome the difficulties met by classical optimal method，the genetic algorithm is used to search for the global optimal solution. At last，the genetic algorithm method is used to inverse the parameters of 2-D wave equations in porous media which has an analytical solution given by Paul in 1976. The numerical results confirm that genetic algorithm is feasible and robust.

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BUILD-UP AND DISSIPATION OF EXCESS PORE WATER PRESSURE IN SATURATED SAND UNDER IMPACT LOADING

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2003, 22 (09): -1463 doi:
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[PDF 344 KB] (1035)

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The shock pressure on saturated sand in a cylinder induced by impact loading is measured. The relation between the amplitude of the shock pressure and the drop-height is analyzed in terms of dimensional analysis. The whole build-up and dissipation process of excess pore water pressure is also measured. The experimental result shows that the mechanism of the build-up of excess pore water pressure induced by impact loading is the same as that induced by cycling loading. Only the increasing ratios and amplitudes of the loadings are different. The maximum value of excess pore water pressure at one point in the sand column is equal to the overburden pressure of the corresponding position. The critical intensity value of mono-impact which may cause the saturated sand to be liquefied completely is obtained. The influence of multi-impacts on the build-up of excess pore water pressure is analyzed. For the dissipation of excess pore water pressure，the experimental results show that the higher the drop-height is，the longer the dissipating time is.

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PORE WATER PRESSURE OF SATURATED STRATUM
UNDER DYNAMIC IMPACTS

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2003, 22 (09): -1469 doi:
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[PDF 250 KB] (1067)

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The distribution characteristics of dynamic stress and pore water pressure of saturated stratum are analyzed during dynamic impacts firstly. Based on these results，the corresponding consolidation equation is established，and the general solution is also given. The dynamic load is considered as a stress pulse course with loading and unloading stage，and therefore，a simplified calculation method is given by dividing the total load into a series of uniform load increments with equal magnitude. In the above analyses，two new concepts of consoli- dation coefficient and pore pressure parameter under unloading condition are proposed. The mechanism of dynamic consolidation is studied. The above studies provide some basic conditions for the calculation of deformation of saturated stratum under dynamic compaction loading.

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DYNAMIC ENGINEERING CLASSIFICATION OF
STOPE ROOF STABILITY

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2003, 22 (09): -1474 doi:
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[PDF 281 KB] (1022)

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The major influence factors on stope roof stability are rock property condition，environmental condition and engineering factor，which should be considered as possible as you can in the scheme of classification of stope roof stability. Five influence factors，such as uniaxial compressive strength of rock，RQD，compressive strength of coal mass，hydrological condition of roof，and advance velocity of stope，are adoped in the classification. The first three factors belong to rock property condition，the fourth belongs to environmental condition，and the fifth belongs to engineering factor. Five network topology structures，such as 5∶5∶1， 5∶8∶1，5∶11∶1，5∶15∶1，5∶20∶1，are adopted with back-propagation artificial neural network in MATLAB language. Based on the errors of training samples，the topology of 5∶20∶1 is the best one. The stability of roof is classified dynamically with the BP network topology structure of 5∶20∶1，in which there are five input neural units，twenty hidden neural units，and one output neural unit. The influence factors are also analyzed with Parato list. According to the magnitude of influence degree on roof stability，there are RQD (0.438 2)，hydrological condition of roof (0.198 8)，uniaxial compressive strength of rock (0.147 2)，compressive strength of coal mass (0.122 5)，and advance velocity of stope (0.093 2).

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EVALUATION AND ANALYSIS ON THE RATIONALITY OF UNDERMINE PATTERNS AND PARAMETERS FOR TUNNELING

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2003, 22 (09): -1478 doi:
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[PDF 172 KB] (979)

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The method of fuzzy theory is developed for optimization of six undermine patterns and relative parameters. The observation data are adopted for optimization，and the results show that the best undermine pattern is the wedge cut pattern. In the burn cuts，the better patterns are the compound cut and spiral cut. According to the actual result，the compound cut，spiral cut and diamond burn cut are recommended in the deep blasting.

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STUDY ON THE UNEVEN GROUND PRESSURE IN PITCHING
OBLIQUE UNDERHAND MINING

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2003, 22 (09): -1483 doi:
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[PDF 238 KB] (1003)

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Based on the study of ground pressure in mining face and roadway through experiments in site and model testing in lab，the behaviors of ground pressure are compared for the pitching oblique underhand mining and straight long-wall mining. The reasons of uneven ground pressure are obtained for pitched oblique underhand mining. Meanwhile，the adaptable parameters in mining face of pitching oblique underhand mining are discussed，and they could be used for the control of ground pressure and optimum design.

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INSTABILITY MECHANISMS OF SOIL SLOPE UNDER DOUBLE DYNAMIC LOADING

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2003, 22 (09): -1489 doi:
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[PDF 276 KB] (908)

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It is common for highway and railway to share the same slope in foothill and mountainous areas. The soil slope there suffers double dynamic loadings，one is the vehicles running on the highway on the top of the slope，and the other is the train trucks acting on the bottom of the slope. According to the loading situation，the variations of maximum unbalance force in the soil elements is discussed，and some interactive problems between the dynamics loading and soil slope are analyzed by means of theoretic analysis and numerical simulation. The study result shows that (1) the effect of vehicle loading on the instability of slope is greater than that of train truck loading，(2) in the same loading situation and environment，in the stability analysis process，the effect of train truck loading on the slope can be ignored for the soil slope with small inclination，and (3) for this sort of soil slope，there would be the potential sliding wedges in the middle areas of the slope surface. Finally，phenomenon of displacement lagging is found in analysis，which appears within the moving soil elements，and seems more evidently in the initial phases before limit equilibrium. In term of the theory of constitutive relations and the property of lagging ring under the circle loading conditions of soil，it is very easy to explain the phenomenon. Because of displacement lagging，the sliding tracks of instable soil wedges become more complicated，and further study is needed to solve this problem.

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STUDY ON TIME FUNCTION OF SURFACE SUBSIDENCE
—— THE IMPROVED KNOTHE TIME FUNCTION

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2003, 22 (09): -1496 doi:
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The Knothe time function was known to be able to describe the whole process of surface subsidence. Through theory proof and comparison with actual measurement data，the fault of Knothe differential equation is discovered in describing the whole process of surface subsidence. By means of analyzing the whole process of surface subsidence，a more objective and reasonable expression for time function of surface subsidence is derived and presented，which has been verified with actual measurement data of Dongpang mine.

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PREDICTION OF GROUNDWATER LEVEL IN LANDSLIDES
BASED ON RADIAL BASIS FUNCTION

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2003, 22 (09): -1500 doi:
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[PDF 194 KB] (941)

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The groundwater system in landslides is a complicated one influenced by many factors. According to the relation between groundwater level and the factors that affect the variation of groundwater level in landslides，the first purpose of groundwater predition is to find out the reasonable boundary condition that is basis for stability analysis of landslides. The second purpose of predition is to find out the variation of stability coefficient versus groundwater level. For these purposes，artificial neural network model which adopts radial basis function is developed，based on the relationship between groundwater level and its influential factors used for the predition of groundwater regime．Case study indicates that the precision of the developed model is rather high and its popularization significance is better than the others models.

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RESEARCH ON STABILITY AND DEFORMATION OF DRY-DOCK SLOPE

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2003, 22 (09): -1505 doi:
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[PDF 212 KB] (1055)

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The stability of dry-dock slope is calculated by simplified Bishop method. The results show that Fs is increased firstly and then decreased. Based on measured data，the horizontal deformation of slope top is changed linearly during excavation stage while logarithmically in service stage，and the deformation during excavation stage is 2/3 of the total deformation. The corner effect ratio Rc is suggested to describe the deformation distribution law changed with space. At last a formula is established to calculate deformation based on Rc and time T.

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STUDY OF DEFORMATION AND FAILURE PROCESS OF SOFT FOUNDATION SLOPE

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2003, 22 (09): -1510 doi:
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Based on the field investigation，the deformation mechanism of a large-scale soft foundation landslide is discussed in the area of hydroelectric power station in the upstream of Yellow River. The soft foundation slope is composed of soft rockmass in lower part and hard rockmass in upper part. It is demonstrated that the evolution of this kind of slide is always initiated by the compression of the lower soft rockmass，then the tension fracture and toppling of the upper hard rockmass occur，and at last the landslide of creep sliding-tensile fracturing type would occur along the shear stress concentration zone in the slope．

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THEORETICAL STUDY AND ANALYSIS OF SITE OBSERVATION ON
THE INFLUENCE OF SHIELD EXCAVATION ON SOFT
CLAYS AROUND TUNNEL

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2003, 22 (09): -1514 doi:
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The main issue considered both in the design and construction in the urban environments is controlling of the ground movement to keep the safety of building adjacent to tunnel and the various underground municipal facilities. The general analysis on the ground disturbance caused by shield excavation shows that the movement of soil around the shield tunnel presents deferent regional characteristics，and the interfaces of various disturbed zones change with the magnitude of pressure on the working face. As the existing underground drainage pipe itself is of given rigidity，the sheltering will affect soils，and may change their moving characteristics. Based on the tunneling of Shanghai Metro Line No.2 in the ground beneath the drainage pipe，by surveying the pore water pressure，ground movement which includes the soil layer settlements，the horizontal soil displacements in two directions in field，the co-relationship between the ground movement and tunneling is studied. The study shows that，while the shield approaching，crossing and leaving the surveying zone，the ground movements in different zone around the Metro Tunnel present respective characteristics.

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CONSTRUCTION OF UNDERGROUND HYDRAULIC STRUCTURES AND TBM TECHNOLOGY IN CHINA

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2003, 22 (09): -1521 doi:
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This paper deals with the construction of underground hydraulic structures and TBM technology in China——past，present and future. China ranks number one in the world in water power. But，the ratio of developed to potential hydropower is only about 20%. The exploitable water power in West China，where is featured by high mountain and complex geology，accounts for 83% of the total for China. Most of the project structures have to be located underground. The projected length of hydraulic underground openings per year is about 180 km. Several underground projects completed，under execution and planned are highlighted in this paper. Finally，general information about the development of TBM technology in hydraulic construction in China is outlined.

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LONG AND DEEP DIVERSION TUNNELS OF 1ST STAGE PROJECT IN WEST ROUTE OF SOUTH-NORTH WATER TRANSFER PROJECT

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2003, 22 (09): -1527 doi:
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West Route of South-North Water Transfer Project，situated in southeastern Qinghai-Tibet Plateau，is a giant project，which will deliver 17 billion m3 of water from the main stream and tributaries upstream of the Yangtze River to the upper reaches of the Yellow River. It is to be constructed in 3 stages， of which the 1st stage project includes delivering 4 billion m3 of water by gravity from two tributaries of Yalong River and three tributaries of Dadu River. The project consists of 5 dams，7 tunnels and a channel in series，with the dam height of 63～123 m and water transfer length of 260.3 km，of which the tunnels measure 244.1 km. The special climatic，environmental and geologic conditions make the project much more complicated in construction，especially 3 tunnels with the length longer than 50 km each create challenges to the technical requirements of engineering survey，design and construction.

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TESTING STUDY ON STRENGTH OF THE ZZLS
MATERIAL FOR EROSION CONTROL OF SLOPE

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2003, 22 (09): -1533 doi:
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ZZLS material is a kind of ecotype revetment material with the functions of higher strength and anti-erosion，and recoverable vegetation. The scanning electron microscope and energy dissipate X-ray techniques are used to analyse the microstructure and cementing composition of ZZLS material，and the mechanism of its growing and strength of this material are studied. The strength of ZZLS material is obtained by unconfined compression test carried out in triaxial test equipment，and the laws of its unconfined compressive strength and modulus of deformation are analysed. The parabolic model is used to simulate the stress-strain relation of ZZLS material，and the testing parameters of the parabolic model are also given. The results show that the porosities of ZZLS material are available to facilitate vegetation. The hydration of cement increases the strength and water stability of the aggregate of the material. The unconfined compressive strength increases with coagulate time and admixing percents of cement，which can be expressed by an exponential function. When the cement added to the material is above 12% of the material weight，the unconfined compressive strength increases significantly with coagulate time. Thus the optimum admixing percents of cement with 12%～15% are suggested in the engineering of erosion control for slope. The parabolic model to describe the stress-strain relation of ZZLS material is very reasonable，and both of the average and ultimate modulus of deformation has a good linear relationship with its unconfined compression strength.

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NUMERICAL STUDY OF LOW STRAIN DYNAMIC TEST FOR BOLT

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2003, 22 (09): -1538 doi:
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Sonoprobe method has been applied in non-destructive inspect of bolt-supported project，with the fundament that dynamic transient excitation causes the elastic vibration of bolt，and flaws can be estimated or dedermined by analysing transient response of bolt. In the mechanics field this method means that if the information of disturbance resource，boundary conditions and initial conditions has been given，the dominant equation describing medium motion could be established and then the dynamic response solved. Usually it comes down to the question of initial value or initial-boundary value of hyperbolic equation or hyperbolic- diffusibility equation. FE solution is made on the hyperbolic equation，based on acoustic parameters，such as velocity of sound，vibration range，wave shape，etc，when inspecting interior flaws of grout of bolt. The obtained estimation is more credible with the spectrum aberration taken into account.

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ANALYSIS ON CONSOLIDATION DEFORMATION OF SAND-WELL FOUNDATION WITH FEM-EFGM COUPLING METHOD

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2003, 22 (09): -1542 doi:
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As a newly developed means of numerical method，the coupling method of finite element method (FEM) and element-free Galerkin method(EFGM) not only is of the advantage of FEM，but also makes the use of the EFGM localization technique and the element-free character. The EFGM is introduced in detail and the FEM-EFGM discrete style of Biot consolidation equation is deduced. Calculations and analyses are made on the pore-pressure and flux of the single sand-well foundation and a site of vacuum preloading. As a result，the comparison of the results of analytical solution and in-situ data shows that the EFM-EFGM is more accurate in calculation and the treatment of boundary，and the solution of fluid flux can conform with practice. Basides，the characteristics of meshless and local approximation indicate that the coupling method is more effective and flexible in both theoretical study and practical application.

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DETERMINATION OF TUNNEL FAULT BY THE METHOD OF FAULT PARAMETER FORECAST

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2003, 22 (09): -1547 doi:
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The forecast method of fault parameter is proposed to determine the strike，dip，location and scale of fault behind the working face with the distinctive joints in effective zone of fault. The principle and quintessence，Liu Zhigang formula，and the key technique of this method are presented for advanced geologic forecast. The available application area and effect are also described with some practical examples.

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INFLUENCE OF SEEPAGE ON GROUND SETTLEMENT OF DEEP FOUNDATION PIT

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2003, 22 (09): -1551 doi:
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[PDF 231 KB] (1546)

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The stress field of soils will change and environmatal ground settle with excavition unloading of deep foundation pit. The seepage induced by lowering groundwater in deep foundation pit results in a seepage field and it could be described by flow net. The well-seepage theory and Dupit formula are applied. Over the flow profile buoyant unit weight of soil is changed to saturated one. Below the flow profile，the consolidation value of soil is incrased with permeable force. The seepage field is coupled with stress field，which is simulated by FEM. The value of ground settlement of foundation pit is acquired. Compared with a practical example，the calculated value is close to actually measured value for a deep foundation pit.

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INFLUENCE OF VARIATION OF ROCKMASS MECHANICS PARAMETERS ON THE DEFORMATION FIELD OF METEORITE IMPACT

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2003, 22 (09): -1555 doi:
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ANALYSIS AND DESIGN OF TIMBER-PILE COMPOSITE
FOUNDATION ON SOFT SOILS

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2003, 22 (09): -1560 doi:
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In design and construction works of soft foundation treatment for the intercepting ditch of sewage in the third-stage regulation works of the Nanjing Inner Qinhuai River，the technique of timber-pile composite foundation is successfully used to solve the problem of building special structure on soft soils with high coefficient of compressibility in ancient riverbed. This technique is proved to be reliable，economical and efficient. The problems of construction，bearing capacity in vertical and horizontal directions and settlement of timber-pile composite foundation are analyzed and solved.

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CRITICAL DYNAMIC STRESS RATIO AND DYNAMIC STRAIN ANALYSIS OF SOILS AROUND THE TUNNEL UNDER SUBWAY TRAIN LOADING

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2003, 22 (09): -1566 doi:
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[PDF 190 KB] (1459)

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Through the dynamic triaxial tests of silt soils around the tunnel of Sang-Shang-Jie station，Nanjing subway，the dynamic strain analysis is made on the silt soils under subway train loading，and the influence of consolidation status of soils，consolidation ratio，axial cyclic stress，vibration frequency are taken into account. The variation rule are obtained of the critical dynamic stress ratio of the silt soils and dynamic strain with vibration times，vibration frequency，confining stress and axial stress. Some conclusions could be made from the research as following. (1) There is a critical dynamic stress ratio under train vibrating loading，which depends on soil property，loading characteristic，and consolidation pressure. Soil deformation increases with cyclic times when applied loading is less than the dynamic critical stress. But the increasing rate slows down until it trends to a constant value. On the contrary，the deformation increases quickly with cyclic times until soil is destroyed. (2) In the same vibration condition，the higher the frequency is applied，the less the deformation is induced. The critical dynamic stress ratio decreases gradually with growing of frequency and there is an asymptote. (3) With the same axial consolidation pressure and dynamic stress，the larger consolidation ratio is，the larger ultimate deformation is and the easier it is to make sample destroyed.

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CALCULATION AND STUDY ON BEARING MECHANISM OF PILE FOUNDATION IN COMPLICATED GROUND

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2003, 22 (09): -1571 doi:
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[PDF 246 KB] (951)

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The interaction mechanism of pile and soil in complicated ground is studied in detail. The limitation and applicability of different methods for solving this problem are analyzed and compared，based on which a new practical model of pile-soil system in multi-layer medium is set up. In combination with improved Mindlin solution，load transfer method，linear deformation layer model，mirror imagine method，optimization and back analysis method，a new generalized elastic theory method is presented to calculate and analyze complicated ground model. The optimization and back analysis program can not only be used to calculate and modify load-settlement curve of a pile，but also to analyze geo-mechanical parameters of ground-pile system on the basis of static load test results of a pile. The values of parameters can be used to supervise the design about bearing performance of a pile. The method and program are validated with engineering cases and proved to be satisfactory.