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  • Rock and Soil Mechanics
    Supervised by: Chinese Academy of Sciences
    Publisher: Science China Press
    Period:Monthly Publication
    Editor-in-Chief:KONG LingWei
    Sponsored by :Institute of Rock and Soil Mechanics, Chinese Academy of Sciences
    Journal Tags: EI
    Language: Chinese
    Release Date: 1979
    ISSN 1000-7598 CN 42-1199/O3
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Fractal characteristics of effective seepage channel structure of water infusion coal based on NMR experiment
YANG He, CHENG Wei-min, LIU Zhen, WANG Wen-yu, ZHAO Da-wei, WANG Wen-di
Rock and Soil Mechanics    2020, 41 (4): 1279-1286.   DOI: 10.16285/j.rsm.2019.0586
Abstract321)      PDF(pc) (9818KB)(13919)       Save
The aim of this study is to quantitatively characterize the structural changes of effective seepage channels in water infusion coal body. The structure characteristics of the coal body under various confining pressures and water infusion pressures are measured via nuclear magnetic resonance (NMR) technology. The fractal characteristics of effective seepage channel in coal body are analyzed with fractal geometry theory. The results show that the coal body with water infusion has an intertwined internal fracture-pore structure and that the pore radius distribution is diverse under the influence of different water pressures and confining pressures. The variation of large pores volume is 13.72%, followed by transitional pores and medium pores of 8.12% and 5.39%, respectively. The smallest micro pores is 2.05%. Combined with the T2C test results, when the pore radius is greater than 270 nm, it is an effective seepage channel, and the pore structure affecting the seepage characteristics of the water infusion coal is mainly concentrated in the large pores and medium pores. In the process of test, the change of fractal dimension of test and theory is small, which shows that the structure of seepage passage of coal sample has obvious fractal characteristics under different pressure conditions. At the same time, the opposite change trend of the two verifies the different significance of their respective characterization.
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Study on integration of three-dimensional modeling and numerical simulation for stratified rock mass
WANG Ming-hua, BAI Yun
null    2005, 26 (7): 1123-1126.  
Abstract2364)      PDF(pc) (574KB)(12436)       Save
The difference between the two grids for three-dimensional visualization and the element for numerical simulation in geotechnics is obvious due to the variety of data structure. Consequently, it is of much importance to study the integration of three-dimensional visual modeling and mechanical analysis. After dissecting mesh properties of the three-dimensional visualization and the numerical simulation, a method of loose mode which converts three-dimensional grid to FLAC3D element is brought forward. Its application to a submarine tunnel proves that it is reasonable and effective.
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Critical problems of study of slabbing failure of surrounding rock in deep hard rock tunnel and research progress
ZHOU Hui , LU Jing-jing , XU Rong-chao , ZHANG Chuan-qing , MENG Fan-zhen,
null    2015, 36 (10): 2737-2749.   DOI: 10.16285/j.rsm.2015.10.001
Abstract1689)      PDF(pc) (945KB)(11159)       Save
Slabbing failure with regularity of surrounding rock is a typical failure phenomenon in deep hard and brittle rock mass due to excavation activity, which poses a serious challenge to safely construct the underground tunnels. There are two critical problems in the research of slabbing failure, i.e. the formation mechanism of slabbing failure and its influencing factors, and the relationship between slabbing failure and rockburst. Remarkable achievements have been made in the slabbing failure by theoretical analysis, field tests, laboratory experiments and numerical simulation over the past decades. By summarizing the research progress related to these two critical problems, it is believed that the formation mechanism of slabbing failure is a complex problem involving various influencing factors. Based on the meso-mechanism of the slabbing failure, the key point to explore its formation mechanism is to establish different types of mechanical criterion and model. Slabbing failure and rockburst have strong correlation and essential connection. To further reveal characteristics of slabbing failure and the involved precursor information of rockburst is a critical and difficult problem to study the relationship between slabbing failure and rockburst.
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Development of static constitutive model library for soils based on ABAQUS
SI Hai-bao, CAI Zheng-yin
null    2011, 32 (2): 599-603.  
Abstract5767)      PDF(pc) (581KB)(8416)       Save

As a powerful universal finite element analysis program, ABAQUS possesses immense ability for nonlinear computing, pre-and-post-processing. But the constitutive model of soil adopted in standard ABAQUS is inadequate in terms of the inability of reflecting militancy of cohesive soil, strain-softening and hardening of sand as well as the impact of stress path on deformation, etc. So it became an emergency for new constitutive model library which is more suitable for soil to be added into ABAQUS. In order to enlarge the computing ability of ABAQUS in the area of geotechnical engineering, new constitutive model library such as Duncan-Chang model, NHRI model and Sand model which are more adaptive for engineering application were developed with the help of secondary development toolkit UMAT as well as data interface. In this way, the convenient pre-and-post-processing and powerful nonlinear solving platform were made full use of in the study, and that more pertinent and more realistic finite element calculation for the stress and strain in soil can be accomplished, which is able to provide technique support for engineering practice. A numerical example is given; and the results verity that the second development of constitutive model library is valid.

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Compressibility and permeability behavior of two types of amended soil-bentonite vertical cutoff wall backfills
DU Yan-jun, FAN Ri-dong
null    2011, 32 (S1): 49-54.  
Abstract3638)      PDF(pc) (619KB)(8058)       Save
Soil-bentonite vertical cutoff walls are effective and economical as engineering barriers for geoenvironmental containment. The compressibility and permeability of zeolite-amended soil-bentonite vertical cutoff walls for the purpose of enhancing the chemical compatibility have not been well addressed. These two engineering properties of soil-bentonite backfills before and after amended with zeolite are assessed via a series of oedometer tests. The results are discussed using the generalized state parameter (i.e. e/eL) and the void index Iv, which are used to analyze the intrinsic properties of remolded clays.
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Reflections on numerical analysis of geotechnical engineering
GONG Xiao-nan
null    2011, 32 (2): 321-325.  
Abstract5222)      PDF(pc) (77KB)(7682)       Save

The investigation report about the application of numerical analysis of geotechnical engineering in China was introduced firstly. Then the key of analyzing geotechnical problems with continuum mechanics and the current situation of geotechnical constitutive theory were discussed; the developing directions of geotechnical constitutive theory was put forward. Finally, the status of numerical simulation in the geotechnical engineering was evaluated. Through above discussions it can be concluded that, the result of numerical analysis is one of the most important back ground for the engineering judgment of geotechnical engineers in the geotechnical engineering analysis; the key of analyzing geotechnical problems with continuum mechanics is to establish simple and practical engineering constitutive model. Establishing many simple and practical engineering constitutive models and accumulating a lot of engineering experience, numerical analysis can be used in geotechnical engineering from qualitative to quantitative.

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An elastoplastic constitutive model based on modified Mohr-Coulomb criterion and its numerical implementation
JIA Shan-po, CHEN Wei-zhong, YANG Jian-ping, CHEN Pei-shuai
null    2010, 31 (7): 2051-2058.  
Abstract4879)      PDF(pc) (786KB)(6956)       Save

Due to the conventional Mohr-Coulomb criterion used for geotechnical materials with its limitation for overestimation of tensile performance, a modified Mohr-Coulomb model is established considering maximal tensile stress criterion. The main contents of the implicit constitutive integration algorithm are discussed systematically; and the consistent stiffness matrix is deduced. Based on the implicit Euler stress integration algorithm, the UMAT subroutine of the modified Mohr-Coulomb model is developed in ABAQUS. With the new developed model, the numerical simulation of uniaxial tensile test and triaxial compression test is implemented respectively. The study shows that the developed modified Mohr-Coulomb UMAT subroutine could effectively depict the tensile performance of geotechnical materials and fill up the deficiency of the Mohr-Coulomb model in ABAQUS.

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Influence of matric suction on shear strength behavior of unsaturated soils
LIN Hong-zhou, LI Guang-xin, YU Yu-zhen, Lü He
null    2007, 28 (9): 1931-1938.  
Abstract2221)      PDF(pc) (518KB)(6904)       Save
It is evident that unsaturated soils are usually encountered in nature and engineering practice. Hence, the understanding of unsaturated shear strength behavior is necessary. The shear strength behavior of unsaturated soils is investigated on the basis of pressure plate test and direct shear test. The results show that the angle of internal friction decreases with increasing degree of saturation and the cohesion attains its peak value at degree of saturation 40 % ? 60 %. According to these results, the unsaturated shear strength behaviors of non-cohesive and cohesive soils are demonstrated. The internal friction angle of non-cohesive soils increases with increasing matric suction; and the pseudo-cohesion attains its peak value in primary transition zone and then decreases. The cohesion of unsaturated cohesive soils increases with increasing matric suction until threshold suction reaches. The threshold suction is the minimum suction at the residual zone of unsaturation. The cohesion of unsaturated cohesive soils can be predicted before the threshold suction, because value is approximately constant. Moreover, the state paths influence cohesion in excess of the threshold suction.
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State-of-art of research on mechanical properties of frozen soils
QI Ji-lin,MA Wei
null    2010, 31 (1): 133-143.  
Abstract4260)      PDF(pc) (599KB)(6591)       Save

China has a large area with seasonally and perennially frozen soils. It is necessary to study mechanical properties of frozen soils for the sake of constructions in cold regions, so as to guarantee their stability. In this paper, the distribution of frozen soils in China and the main features of frozen soils differing from unfrozen soils, are briefly described firstly. Generally speaking, frozen soil mechanics consists of two main aspects, i.e. freeze-thaw related problems and mechanical properties of the already-frozen soils. Frost heave, thaw settlement and freeze-thaw induced changes in mechanical properties are freeze-thaw related problems. Frost heave has been extensively studied. Various theories have been put forward to describe the mechanism of ice segregation which is considered as the main cause of frost heave; and some theories have even been applied to quantitative analysis. The study of thaw settlement has a long history, while most of the previous studies still stay in empirical stage. Thaw consolidation has been studied; but it has considerable limitations so far. Therefore, we suggest that the artificial neural network could be used to improve the precision and applicability in estimating thaw settlement on the one side, large strain theory could be used to improve thaw consolidation theory. For the already-frozen soils, this paper summarizes the previous studies on strength, stress-strain relationship and dynamic properties. Study of the strength of frozen soil borrows strength theories for unfrozen soils; however, they can hardly reflect stress melting of frozen soils under high stresses. The previous studies of stress-strain relationship of frozen soils have been focusing on creep; and the empirical relationship directly obtained from testing data is the mainstream. Influence of temperature on dynamic parameters of frozen soils seems to be the only task in frozen soil dynamics for a long time; while influence of frozen layer in dynamic response of a site has attracted attentions in recent years. At last, physico-mechanical processes involved in deformation of constructions in permafrost regions are briefly analyzed.

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Basic mechanical behavior of soils and their elastoplastic modeling
YAO Yang-ping, HOU Wei
null    2009, 30 (10): 2881-2902.  
Abstract6390)      PDF(pc) (819KB)(6453)       Save

Based on the study of the isotropic loading test, the Cam-clay model has been established as the simplest elastoplastic model to describe the stress-strain relationships of normally consolidated clay in triaxial compression test, which is the basis to propose other models. According to the difference in loading modes and fabric characteristics, elastoplastic models describing stress-strain relationships under loading modes related to stress state, stress history, stress paths, loading time etc. are summarized. And elastoplastic models describing behaviors of soil structure, anisotropy and particle crushing etc. are summed up as well. Also, the transformed stress method representing the three dimensional property of soils, over-consolidated clay model describing the stress history effect and the asymptotic state model simulating asymptotic state path are introduced in detail.

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Numerical analysis of bearing characteristics of composite subgrade reinforced by chemical churning pile groups
AN Guan-feng, ZHANG Hong-bin, LIU Tian-jun
null    2012, 33 (3): 906-912.  
Abstract3215)      PDF(pc) (1139KB)(6452)       Save
The method of soft soil subgrade reinforcement with chemical churning pile is used more and more in projects of subgrade treatment. At present, the researches about chemical churning pile usually focus on improvement in construction techniques or bearing characteristics of single pile. But research about bearing characteristics of chemical churning pile groups is not much. Based on MIDAS-GTS three-dimensional finite element analysis, the influence of design parameters on bearing characteristics of chemical churning pile groups is studied. These design parameters of chemical churning pile include layout, elastic modulus, length, diameter of piles, and distance between piles, the parameters of interface between piles and soil. The results show that the vertical settlement of soil within the range between surface and pile bottom is reduced in soft soil subgrade reinforced by chemical churning piles; but the method has little effect on the vertical settlement of soil under pile bottom. Larger pile diameter and higher material strength can improve the bearing capacity of composite subgrade. But different layouts of chemical churning piles and whether to set up Goodman interface element have little influence on bearing capacity of composite subgrade.
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Practical calculation method of retaining structures for deep excavations and its application
YANG Guang-hua
null    2004, 25 (12): 1885-1896.  
Abstract1219)      PDF(pc) (760KB)(6054)       Save
A systematic and practical method of calculation of internal forces and deformation of retaining structure for deep excavation is put forward; and by the method, the design of retaining structure for deep excavation can be perfectly finished. The method is applied to the deep excavation project of Guangzhou metro and other important projects; and it is proved to be effective and available .It simplifies the structure as an elastic beam on ground; and the braces, rock and soil are simplified as a spring system; the rock and soil springs can be express by the deformation modulus of the rock or soil. The systematic calculation method also includes the incremental calculation method that can be used to modeling the construction process, obtaining the embedding depth of the retaining structure reasonably; and it also can be used to modeling the preloading of the brace and the dismantling of the brace etc.. The famous Terzaghi-Peck apparent earth presure is firstly explained preferably by this method. The experiential calculated method for deformation modulus of soils by the bearing capacity is presented. The systematic calculation method provides an effect calculated method of retaining structure for deep excavation; and a series of key problems are solved preferably by the method. It is applied triumphantly in practice.
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Extended finite element simulation of hydraulic fracture based on ABAQUS platform
GONG Di-guang, QU Zhan-qing, LI Jian-xiong, QU Guan-zheng, CAO Yan-chao, GUO Tian-kui
null    2016, 37 (5): 1512-1520.   DOI: 10.16285/j.rsm.2016.05.036
Abstract2277)      PDF(pc) (1602KB)(6047)       Save
With the further study of the extended finite element theory, the extended finite element method (XFEM) has been widely used to simulate hydraulic fracturing. In comparison with the conventional FEM, the XFEM method has substantial advantages, such as high precision and low computational complexity. However, there are still many difficult challenges including how to simulate the perforation and the interaction between fluid and rock and to analyze propagation law of hydraulic fracturing. In this paper, to study the propagation law of hydraulic fracturing, the stress equilibrium equation of rock porous medium, fluid continuity equation and boundary conditions are established. Through finite element discretization method, the coupling equation matrix is treated. The initial fracture (or propagation) is defined through enrichment functions, and the maximum principal stress and damage variable D are selected respectively as the criterion of fracture initiation and propagation. Hydraulic fracturing propagation process is simulated by using the level set method. Numerical results show that the increase of perforation azimuth, fracture fluid displacement and the reduction of the horizontal stress difference cause the increase of the fracture initiation pressure, and the viscosity has no obvious effect on the fracture initiation pressure. It helps to widen the fracture width by increasing the perforation azimuth, the fracturing fluid displacement, the fracturing fluid viscosity and decreasing the horizontal stress difference. Increasing the horizontal stress difference, fracturing fluid displacement and decreasing the perforation azimuth and the viscosity of fracturing fluid can help to increase the fracture length and vice versa. Different well types and parameters of reservoir and fracturing operation are analyzed by hydraulic fracture XFEM based on ABAQUS platform. The fracture shape is lifelike and the image of degree of concave-convex on the fracture surface is clear. In consequence the result is accurate. As a simple and effective research method for studying the criterion of hydraulic fracturing propagation, this study provides the reference for hydraulic fracturing design and operation in oil field.
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Determination of dilatancy angle for geomaterials under non-associated flow rule
KONG Wei-xue,RUI Yong-qin,DONG Bao-di
null    2009, 30 (11): 3278-3282.  
Abstract4402)      PDF(pc) (527KB)(5869)       Save

Geomaterials are frictional materials, and their strength indexes play a key role in depicting strength characteristics. Illegible knowledge on dilatancy angle has existed for a long time, which caused large errors in theoretical analysis and numerical simulation. It was proved with the generalized geotechnical plastic mechanics principle that the angle of dilatancy should be ? /2 and the corresponding volumetric strain is zero for geomaterials under non-associated flow rule, based on traditional slip line theory. The classic foundation bearing capacity topic of Prandtl’s solution, which has accurate theoretical interpretation, was analyzed systemetically with step loading finite elements under the following three conditions: 1) associated flow rule, 2) non-associated flow rule with the dilatancy of ? /2 and 3) non-associated flow rule with the dilatancy of 0. Results showed that the errors of ultimate capacity obtained under the above three conditions were within 2 %, but the slip line fields were quite different. The slip line field obtained under conditon 2) was identical with that by Prandtl’s solution, but a large deviation existed between condition 3) and Prandtl’s solution. Thus a correct ultimate load and a slip line field with a great error can be acquired under condition 3), but both are precise under condition 2). Therefore, the angle of dilatancy should be ? /2, not 0 widely used at present when non-associated flow rule is applied.

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Study of the technology of 3D modeling and visualization system based on Python
LIU Zhen-ping, HE Huai-jian, LI Qiang, ZHU Fa-hua
null    2009, 30 (10): 3037-3042.  
Abstract3394)      PDF(pc) (680KB)(5751)       Save

It is studied profoundly that the compound 3D visualization modeling system can be built up with the open-sourced graphic libraries PYOpenGL and VTK. In this process, the computational models written by Python and other models written by C or C++ can be invoked successfully when we use the python language as a kind of adhesive and wxPython as GUI with the help of swig. Moreover, a kind of data structure is implemented using the Quad-edge data structure as prototype, which makes the topology more compact and queries more efficient. Then based-on this data structure, spatial discrete points Delaunay triangulation in any plane is accomplished through the setting of projection plane. Taking full advantage of the topology characteristic, a kind of algorithm which can search interrelated triangles, segments and vertexes efficiently is obtained; and the object of inserting any constraint is reached. Up to now, the function of loading geometry data and other information stored in the format of DXF, Excel or TXT files or access and SQL Server DB is made reality. Also in the system, many general 3D modeling functions as interpolations of inverse distance, Kriging and cubic spline, Delaunay triangulation, constraints insertion, intersections with two TIN and so on are accomplished.

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Fractal characteristics of size distribution and shear strength of bulky rock material in waste pile of mines
XIE Xue-bin, PANG Chang-liang
null    2004, 25 (2): 287-291.  
Abstract1122)      PDF(pc) (480KB)(5695)       Save
The fractal characteristics of size distribution of bulky rock material in dumping site of mines are studied by using fractal geometry theory. The quantitative equations reflecting the relation between fractal dimensions and shear strength parameters are also put forward. It is found that there is an excellent fractal structure of size distribution of bulky rock material in waste dump, the value of fractal dimension increases with the increasing height of waste pile, but it is not over 3. The results also show that if the scope of measuring scale is unvaried, the contents of fine grain increases and the average grain-size decreases with the increasing value of fractal dimension. The correlation between the value of fractal dimension and the friction angle which is the shear strength parameter is negative exponential. The value of fractal dimension can be used in predicting shear strength and as a kind of measure in the size statistical analysis of bulky rock material in waste dump.
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Numerical implementation of implicit integration algorithm for modified Cam-clay model in ABAQUS
FAN Qing-lai , LUAN Mao-tian , YANG Qing
null    2008, 29 (1): 269-273.  
Abstract2050)      PDF(pc) (424KB)(5621)       Save
The subroutine UMAT special for user-defined material model in the commercial FEM software ABAQUS is utilized and the implicit integration algorithm for the modified Cam-clay model is numerically implemented in ABAQUS. Combined with automatic time increment method for solving incremental finite element equation, the triaxial drained and undrained shear tests of normally consolidated soil and heavily overconsolidated soil are simulated using ABAQUS with the proposed implicit integration algorithm. The robustness and accuracy of the numerical analyses are illustrated. It is shown that the computational results are valid and can well agree with other solutions available.
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Rigorous solution method for bearing capacity of rotating ground under eccentric loads
JIANG Peng-ming , LU Chang-feng , MEI Guo-xiong , NI Jun , YUAN Hua-rong
null    2008, 29 (11): 2957-2961.  
Abstract1785)      PDF(pc) (407KB)(5582)       Save
Based on the characters of ground failure under eccentric loads, the discontinuous stress fields and discontinuous velocity fields are constructed. The characters of discontinuous lines of stress and velocity are analyzed. By upper and lower bound theorems, the model of calculation and the method for bearing capacity are given. The stress fields and the corresponding mobile fields are obtained by the numerical calculation to solve three kinds of boundary value problems. The stress fields satisfied with all velocity boundaries are found. The rigorous solution of bearing capacity under eccentric loads is solved. The computation results show that the method proposed to solve the limit equilibrium problem is available.
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Relationship between effective stress intensity index and total stress intensity index
CHEN Juan
null    2011, 32 (2): 471-473.  
Abstract3871)      PDF(pc) (342KB)(5554)       Save

When the soil specimens are ruptured the rupture angle , which is obtained from the calculation using the total stress intensity index is not the real rupture angle. It is only a hypothetical rupture angle. Corresponding to the hypothetical rupture angle is the hypothetical shear rupture surface. According to the results of the tests, it is concluded that the real rupture angle is obtained from the calculation using the effective stress intensity index when the soil specimens are ruptured. It is analyzed and demonstrated that, in the shear strength calculation formula of the soil related, the effective stress intensity index and the total stress intensity index can not be confused. And in the formula, the effective stress intensity index should correspond to the effective stress; the total stress intensity index should correspond with the total stress.

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Research situation of open-pit mining high and steep slope stability and its developing trend
YANG Tian-hong , ZHANG Feng-chun , YU Qing-lei , CAI Mei-feng , LI Hai-zhou
null    2011, 32 (5): 1437-1451.  
Abstract5133)      PDF(pc) (562KB)(5484)       Save
Based on the collection and review of the domestic and foreign literatures related to rock slopes, the situations and future development of slope stability analysis and monitoring are summarized in the aspect of methods for rock slope analysis, monitoring and forecast approaches. And especially, the characteristics of open-pit slope are analyzed in detail. The questions existing in the studies of open-pit slope stability are also pointed out. Further, a thought that the progressive damage evolution namely acoustic emission is the nature of rock slope instability is proposed; and the future development of studies of rock stability as well as forecasting methods are given. Firstly, the model which can calculate damage of rock slope from back analysis of the basis of microseismic monitoring data should be built; and the characterization methods of strength parameters of rock mass and evaluation methods of dynamic stability in open-pit slope engineering should be developed. These can give objective evidence to the strength reduction method for rock slope and provide mechanical basis for microseismic monitoring. Secondly, the relationship between microseismic activity, degradation of rock mass strength and slope dynamic instability will be investigated. Finally, precursory information of microseism and safety factor of slope are selected to form combined unstable criterion; and the prediction of rock slope instability and dynamic analysis of open-pit slope stability can be realized
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Analysis of earthquake induced permanent deformation of rockfill dam considering residual volumetric strain
LIU Han-long、 FEI Kang、
null    2013, 34 (6): 1687-1695.  
Abstract2583)      PDF(pc) (675KB)(5279)       Save
The earthquake induced permanent deformation is a key index for aseismic safety evaluation of rockfill dam. In order to calculate the permanent deformation reasonably, both residual volumetric strain and residual shear strain induced by the earthquake loading should be taken into account. For this reason, the method presented by LIU Han-long is modified. In the modified method, the residual volumetric strain is modeled by a shear-dilation-based approach. The derivation of the dilatancy modulus matrix is given in detail; and the calculation parameters and the analysis steps are also introduced. To test the reliability of dilatancy modulus matrix, the permanent deformation mode of a typical element is analyzed, the computed shear strain and volumetric strain are in good coincidence with the theoretical values. After that, the proposed method is used to calculate the earthquake induced permanent deformation of a core rockfill dam and a concrete faced rockfill dam. The computed distributions of the vertical, longitudinal and transversal permanent displacements are studied in detail. By comparing with the measured results, it is found that the dam deformations are mainly residual settlement; and the horizontal displacements are relatively small. It is proved that the proposed method can catch the features of the permanent deformation behavior of rockfill dam and it can give more reasonable results.
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Review of stabilization/solidification technique for remediation of heavy metals contaminated lands
DU Yan-jun,JIN Fei,LIU Song-yu,CHEN Lei,ZHANG Fan
null    2011, 32 (1): 116-124.  
Abstract4071)      PDF(pc) (4110KB)(5160)       Save

Recently, stabilization/solidification of heavy metals contaminated soils (HMCS) using lime, cement, and other binders has been widely adopted in geoenvironmental engineering practice. In this paper, the mechanisms of heavy metal-soil-binder interaction are overviewed based on literature studies. The performance of various leaching test standards for solidified HMCS is compared and discussed. The unconfined compression strength properties and influencing factors of solidified/stabilized heavy metal contaminated soils are also presented. The leaching properties, durability and long-term performance of HMCS from domestic and international studies are summarized. Finally, based on the current studies in China, it is suggested that the minimum strength requirement of HMCS should be given; and test specification of dynamic leaching tests should be built as the assessment criteria of contaminated lands remediation.

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Secondary development of ABAQUS and its application to static and dynamic analyses of earth-rockfill dam
FEI Kang,LIU Han-long
null    2010, 31 (3): 881-890.  
Abstract4530)      PDF(pc) (698KB)(5108)       Save

On the basis of subroutine UMAT provided by ABAQUS,the Duncan nonlinear elastic model for static analysis and the equivalent linear model for dynamic analysis are implemented; so the database of constitutive model in ABAQUS is enlarged. The methods to model layered construction of dam, correct the displacement of new fill layer, consider the effect of wetting effect, evaluate liquefaction resistance of dam material and compute the permanent displacement induced by earthquake are described in detail. The results of examples are found to be reasonable and reliable, it verifies that ABAQUS can be used in static and dynamic analyses of earth-rockfill dam after the secondary development. The present method can make use of the advantages of ABAQUS, such as convenient preprocessor and postprocessor, high solution precision and high ability to handle complex problems; so an alternative method for static and dynamic analyses of earth-rockfill dam is provided.

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Secondary development and application of unified elastoplastic constitutive model to ABAQUS
PAN Xiao-ming, KONG Juan, YANG Zhao, LIU Cheng
null    2010, 31 (4): 1092-1098.  
Abstract4568)      PDF(pc) (7513KB)(5073)       Save

Based on finite element theoretical scheme of unified elastoplastic constitutive model, and according to the UMAT interface requirement of ABAQUS, the corresponding UMAT codes are programmed, which will be called by the main analytical module of ABAQUS. Adopting degenerative model of the unified strength ( ,Mohr-Coulomb model) and the built-in Mohr-Coulomb model of ABAQUS, the uniaxial tests and circular chamber are analyzed to verify the correctness and efficiency of the developed material subroutine. Finally, considering the general situation form of unified elastoplastic constitutive model ( ) and hard condition of yield surface, which are not available in ABAQUS software, circular chamber is simulated and variational discipline of stress field is obtained. The provided basic procedures and programming essentials of the UMAT redefining in ABAQUS are universal and can offer a reference for other developers.

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Estimation of rock mass parameters based on quantitative GSI system and Hoek-Brown criterion
HU Sheng-ming,HU Xiu-wen
null    2011, 32 (3): 861-866.  
Abstract3575)      PDF(pc) (548KB)(5017)       Save

Compared with Mohr-Coulomb strength criterion, Hoek-Brown strength criterion considers more influential factors such as the rock structure, rock mass strength, rock mass stress state,and so on. It reflects the nonlinear failure characteristics more accurately and consists with practical rock engineering much better. The estimated mechanical parameters of rock masses based on Hoek-Brown strength criterion could provide important reference for ultimate determination mechanical parameters of rock masses. A quantitative geological strength index (GSI)rock mass classification system based on volumetric joint count Jv and joint condition factor JC and Hoek-Brown strength criterion can estimate mechanical parameters of rock masses, and connected with the practical engineering to verify its application effect. The results will provide important guiding significance to engineering design and construction.

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Theoretical analysis and numerical simulation of effect of unloading hole under explosive loading
CUI Chua-an, SUN Yun-hou, LI Yong-tao, LI Da-peng. WANG Zi-jia
null    2011, 32 (S1): 669-0673.  
Abstract3658)      PDF(pc) (2277KB)(5012)       Save
The sap engineerings have important function in war; at the same time,it is ease to be struck by cannonballs. In order to increase the protection capability of the sap engineerings, the basic theories and energy dissipation of wave are used for analytical research on rock deformation, energy dissipation during the process of rock friction and the propagation characteristics of explosive stress wave which passes through the interface between rock and air. Based on six conditions of normal working environment ,the numerical simulation results for the inspection nodes are simulated by finite element analysis software ANSYS—LS-DYNA . Comparisons with the theoretical analysis show that the unloading hole plays its role of reducing explosive loading. So that a new way for the protection design of sap engineerings is offered.
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Extended finite element method for modeling three-dimensional crack problems
YU Tian-tang
null    2010, 31 (10): 3280-3285.  
Abstract4158)      PDF(pc) (974KB)(5010)       Save

The extended finite element method (XFEM) is a new numerical method for modeling strong as well as weak discontinuities within a standard finite element framework. The computation mesh in XFEM is independent of the discontinuities, such that re-meshing for moving discontinuities can be overcome. An extended finite element method for modeling three-dimensional crack problems is described. In order to model the crack discontinuity, a Heaviside step function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation for the local enrichment by using the framework of partition of unity. The crack is described with two level set functions. The nonlinear contact conditions between the crack faces are resolved with the linear complementary method; the iterative procedure is avoided. Stress intensity factors of crack front are obtained with two-point displacement extrapolation method. Three examples for three-dimensional elastostatic problems are given; the results show that the method can obtain high accurate stress intensity factors and effectively treat the contact problem between crack surfaces, and the combination of the XFEM and linear complementary method has wonderful practical merits for solving discontinuous problems.

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Application of 3-D GIS to monitoring and forecast system of landslide hazard
WANG Wei,WANG Shui-lin,TANG Hua,ZHOU Ping-gen
null    2009, 30 (11): 3379-3385.  
Abstract5073)      PDF(pc) (1106KB)(4959)       Save

To reduce or eliminate the damage caused by geologic disaster, based on the data of geological mapping and monitoring, it is vital to build a visual monitoring and forecast system of geological hazards by using advanced computer and 3-D visual techniques. We first use TIN method to build 3-D geological model, which are integrated with the data achieved automatically and conveyed by North Satellites; and then, using time-series based techniques, we analyze these data and build a complete 3-D monitoring and forecast system of slope disaster, and provide numerous applicable GIS tools such as section analysis tool, etc. As a result, the quickness and visual of warning of landslide disaster are enhanced. Finally, to validate the system, we examine the project of Xiakou landslide of Ya’an, Sichuan province.

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Application of digital image processing to rock mesomechanics
CHEN Cong-xin, LIU Xiu-min, LIU Cai-hua
null    2010, 31 (S1): 53-61.  
Abstract4079)      PDF(pc) (732KB)(4954)       Save

The internal mesomechanical constitution and structure of rock determine the stress and strain distributions; and hence control the failure mechanism and process of the rock under to loading. The digital image processing (DIP), adopted as a tool of precise measurement and digital representation for the spatial distribution of different components of geomaterials, has been widely applied to the internal structural quantitative analysis of rock at the meso-level. The digital image processing is currently taken as an innovative method for investigating the rock mesomechanical behavior. At present the relevant researches mainly focus on: non- contact measurement of rock fracture aperture, digital representation of rock heterogeneity, analysis of rock mesomechanical behavior, establishing correspondence of rock’s numerical characteristic with its physico-mechanical properties in order to achieve fluid and solid coupling mechanisms, establishing numerical simulations for rock mesomechanics. Based on a comprehensive review of related researches documented in literatures, this paper investigates and discusses in detail the characteristic and development of the digital image processing in quantitative analysis of various rock mesomechanical problems; and analyses the advantages and shortcomings of these research methods. The digital image processing has a great potential to be developed and utilized in rock engineering due to its proved efficacy in measuring geomaterial spatial distributions.

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Theoretical study of microscopical mechanisms and computational method of hysteresis in SWCCs
HE Wei, ZHAO Ming-hua, CHEN Yong-gui, WANG Hong-hua
null    2010, 31 (4): 1078-1083.  
Abstract4211)      PDF(pc) (17860KB)(4932)       Save

The fundamental mechanisms responsible for drying/wetting hysteresis in the relationship between metric suction and water content, and relevant computational method were studied. The difference between drying and wetting contact angles was considered as the principal factor in terms of microscopic view. Then, based on thermodynamic principle and the assumption that the meniscus among soil particles is a crown face, the iteration relation of filling angles was deduced by studying geometrical properties and taking into account the factors such as radius ratio of soil particles and wetting/drying contact angles. And the relationship between suction and volume of filled water among soil particles with different radii was developed by introducing formulas which solve intensity of pressure on meniscus and volume of filled water. The soil-water characteristic curves (SWCCs) of single meniscus and soil particles with different accumulation styles were solved; the results indicate that: the change of contact angles will cause the hysteresis of SWCCs; filling the pore between particles will raise the water content in lower suction status; and it is more remarkable for loose particles, in which the water content can be enlarged by 90%; the influence of accumulation style and graduation of soil particles on hysteresis is paltry comparatively. Besides, the hysteresis loop of SWCCs can not be interpreted only by hysteresis of contact angles, the relevant theory still under developing.

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Study of permeability in single fracture under effects of coupled fluid flow and chemical dissolution
SU Bao-yu,ZHANG Wen-jie,SHENG Jin-chang,XU Xiao-chen,ZHAN Mei-li,LIU Ji-shan
null    2010, 31 (11): 3361-3366.  
Abstract4617)      PDF(pc) (1059KB)(4828)       Save

A two-dimensional numerical model of coupled fluid flow and chemical dissolution processes in single fracture is presented in order to understand permeability changes of single rock fracture in the coupled fluid flow and mineral chemical dissolution processes. The numerical model is solved by using a COMSOL Multiphysics-based simulator, which is the first engineering tool that performs partial differential equation-based multiphysics modeling in an interactive environment. The model is validated through comparing our numerical results with the known experimental measurements in salt rock reported by the reference [1], which shows our model is credible. A rough fracture is generated numerically by using fractal theory and used in the simulation of coupled fluid flow and mineral chemical dissolution processes of a rough fracture in limestone. The simulated results indicate that: (1) The solute concentration plays an important role on the dissolution process; this causes that the dissolved thickness at inlet is bigger than that at outlet. (2) The permeability of fracture increases exponentially with time during the dissolution process.

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A small strain constitutive model based on hardening soil model
WANG Hai-bo,XU Ming,SONG Er-xiang
null    2011, 32 (1): 39-43.  
Abstract3612)      PDF(pc) (456KB)(4788)       Save

A lot of on-site monitoring results show that the soil around many underground constructions is still in a state of small strain under working loads. It is important to consider the soil’s small strain stiffness and stress-path dependency in analyzing interaction between soil and structure. Hardening soil model can define loading-unloading characteristics, however, it can not accurately simulate nonlinear modulus because unloading-reloading modulus is not associated with stress and strain level. In this paper, unloading-reloading modulus of hardening soil model is modified so that it is related to both stress and strain levels; and unloading shear strength and scant stiffness of lateral unloading stress path are also considered specially. Finally, the model results are compared with soil stress-path test results to prove the reasonableness of the model.

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Mechanical and deformation characteristics of enclosure structure for annular extra-deep excavation
LUO Yao-wu, LING Dao-sheng, CHEN Yun-min, HU Qi, CHEN Zheng
null    2011, 32 (2): 617-622.  
Abstract3644)      PDF(pc) (624KB)(4711)       Save

Based on the deep excavation of Shanghai 2010 Exposition 500 kV substation, the plane strain and axisymmetric elastic foundation FEM are used to simplify the space effect of the enclosure structure. The space effect of the annular enclosure structure, the inner liner and the different water and soil pressure distribution model are considered for the mechanical and deformation characteristics of enclosure structure. Through comparision between the calculated and measured results, several results are obtained: the space effect of the annular enclosure structure has a great influence on the mechanical and deformation characteristics of it; the ring stiffness of the enclosure structure must be considered during calculation; the inner liner is beneficial to the mechanical and deformation of the diaphragm wall, like a ring supporting; the measured horizontal displacement of the diaphragm wall is close to the result of axisymmetric finite element analysis when lateral pressure coefficient is 1.0; the measured hoop stress and bending moment of diaphragm wall are between the result of estimating water and earth pressure separately and lateral pressure coefficient is 1.0.

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Deformation monitoring and data processing of landslide based on 3D laser scanning
XU Jin-jun, WANG Hai-cheng, LUO Yu-zhen, WANG Shang-qing, YAN Xue-qing
null    2010, 31 (7): 2188-2191.  
Abstract4062)      PDF(pc) (626KB)(4710)       Save

3D laser scanning technology has been successfully applied to static surface measurement because it can measure 3D coordinate with high speed, high precision and high density to describe the surface detail. At present, the deformation analysis of the landslide surface is carried out mainly with some observed characteristic points by GPS or total station, but because of few data, this analysis is not complete. The detailed deformation of landslide has an important role for the correct deformation analysis. To introduce this technology to the landslide monitoring is significant for detailed deformation analysis, if a lot of natural rocks are used as monitoring points. In this paper, the theoretical analysis and the practical tests have been carried out; and the preliminary result has been obtained.

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Numerical simulation of relationship between thermal conductivity of porous material and fractal dimension
LI Shou-ju, LIU Ying-xi, YU He
null    2009, 30 (5): 1465-1470.  
Abstract3935)      PDF(pc) (674KB)(4669)       Save

The relationship between thermal conductivity of porous material and fractal dimension is numerically simulated by using finite element method. The solid matrix and pore space are generated randomly according to material porosity;and material parameters and element properties are changed by ANSYS parameter design language. The effective thermal conductivity is computed according to thermal flux through some section computed by FEM and Fourier heat transform law. The investigation shows that the effective thermal conductivity linearly decreases with increasing porosity; the effective thermal conductivity of FEM model will increase in exponential function with the increase of scaling factor while the material porosity is constant. The effective thermal conductivity will decrease in exponential function with the increase of fractal dimension of porosity space and increase in exponential function with the increase of fractal dimension of solid matrix

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Study of characteristics of compression capacity and negative skin friction for belled wedge pile
KONG Gang-qiang, YANG Qing, NIAN Ting-kai, HU Qing-chun
null    2011, 32 (2): 503-509.  
Abstract5943)      PDF(pc) (1103KB)(4666)       Save

Based on conventional belled pile and wedge pile, a new type pile, belled wedge pile, which can improve pile shaft friction, tip resistance and reduce the influence of negative skin friction is developed. The stress mechanism and construction method of belled wedge pile is briefly introduced. Based on FLAC3D, The results are verified by engineering examples analysis; the mechanical properties on compression capacity and negative skin friction of belled wedge pile is preliminary studied. Conventional belled pile, wedge pile and equal section pile which are in the same concrete volume are comparatively analyzed. The mechanical properties of belled wedge pile which influenced by modulus ratio of pile end soil and pile surrounding soil, wedge angles, the diameter of enlarged pile head and the modulus of pile are discussed. It is shown that, when in the same surface load grade, the downdrag of belled wedge pile is minimum; the dragload of belled wedge pile is between the values of conventional belled pile and wedge pile.

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Advances of soil improvement with bio-grouting
QIAN Chun-xiang ,WANG An-hui ,WANG Xin ,
null    2015, 36 (6): 1537-1548.   DOI: 10.16285/j.rsm.2015.06.003
Abstract1966)      PDF(pc) (4919KB)(4640)       Save
As cementing materials, cement and chemical grouts have often been used for soil improvement. However, high energy consumption, high-pollution discharge and high cost restrict their applications. A new soil improvement method, called bio-grouting reinforcement technology, has recently emerged, which is based on microbial induced calcite precipitation by injecting bacteria solution and nutrient into loose sand for the purpose of binding soil particles together and improving its physico-mechanical properties. Laboratory and field experimental studies of bio-grouting treated soils are systematically summarized. The engineering characteristics of bio-treated soils, non-destructive geophysical process monitoring method, and factors influencing the improvement effect are also discussed. The research results show that the bio-grouting process has many advantages such as small disturbance, low grouting pressure, less environmental harm, and remarkable treatment effect on improving the engineering properties of the soil (e.g. strength, stiffness, liquefaction resistance), which make it a broad engineering application prospect in soil improvement. However, the durability of bio-treated soils and economy of bio-grouting still need discussing and investigating further.
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Study of construction mechanical behavior of parallel-small spacing metro tunnels excavated by shield method and cross diaphragm (CRD) method in loess region
KONG Xiang-xing, XIA Cai-chu, QIU Yu-liang, ZHANG Li-ying, GONG Jian-wu
null    2011, 32 (2): 516-524.  
Abstract4950)      PDF(pc) (1194KB)(4635)       Save

Abstract: Urban rail transit in Xi’an is the first metro tunnel constructed in loess region in China. In order to meet the functional requirements of double line normal running and enlarged inner section of the right stabling yard in line 1 between North Zaoyuan Road and Hancheng Road(K12+792.744-K12+889.899), construction scheme with the combination of shield method and cross diaphragm (CRD) method is chosen, in which the left tunnel with small inner section is excavated by shield method and the right one with large inner section is constructed by CRD method. 3D-FEM model is established to analyze the construction process and mechanical behaviors. According to the results of the finite element analysis, the settlements of the ground, the stress distribution in the middle soil pillar and the development of plastic zones in the surrounding rocks are discussed. Based on the discussions, the reciprocal influences of construction sequences on the two neighboring tunnels excavated by shield method and CRD method respectively are demonstrated. It is shown that the excavation of anteceding tunnel with large cross-section by CRD method has greater influences on the ground settlement above the subsequent tunnel with small cross-section. In addition, the transfixion of the subsequent tunnel results in the ground settlement axis formed during the excavation of the anteceding tunnel offsetting a distance about a half of the net spacing toward the subsequent tunnel; and the ground settlement caused by the anteceding tunnel excavated increases near the side of the subsequent tunnel. Furthermore, the stress of middle soil pillar is influenced more significantly by the excavation of the anteceding tunnel with large cross-section than that of the subsequent tunnel with small cross-section; and the greater interactive influence caused by parallel tunnels exists near the same excavating face. The research results based on the metro project in Xi’an city will provide valuable practice experiences and worthful research achievements for future construction of other metro tunnels in loess region.

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In-site test on earth pressure and saturating collapse test for unsaturated loess Q3 on high slope
LI Jia-gui, CHEN Zheng-han, HUANG Xue-feng, LI Jia
null    2010, 31 (2): 433-440.  
Abstract4530)      PDF(pc) (1141KB)(4592)       Save

In order to obtain the distributed rule of the earth pressure for unsaturated loess Q3 at the original state and its rules of changes during the process of excavating or saturating, an in-site test was done on an 18 m high slope, which included displacement, earth pressure, suction and the process of collapse. Meanwhile, a series of indoor triaxial shear tests on unsaturated loess Q3 at the original state were also conducted. The outcome as follows: ①For the unsaturated loess Q3 at the original state, the relation between the apparent cohesion and suction is nonlinear, between the effective friction angle and suction is nonlinear too. ②The earth pressure of unsaturated loess Q3 at the original state increases with the excavating depth, which results in the shape of triangle at the end of excavation, high in the middle, low at the two ends; and the maximum earth pressure at the 1/3 height of the slope. Compared with the calculated result from Rankine’s theory, the tested earth pressure is relatively lower, whereas it increases rapidly on the condition of saturation. In short, saturation is the direct cause of the slope collapse.

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A cooperative optimization method based on particle swarm optimization and Gaussian process for displacement back analysis
SU Guo-shao, ZHANG Ke-shi, Lü Hai-bo
null    2011, 32 (2): 510-515.  
Abstract4329)      PDF(pc) (663KB)(4581)       Save

Aiming to the problem about expensive cost and low efficiency of stochastic global optimization technology for displacement back analysis in geotechnical engineering, a novel cooperative optimization algorithm based on particle swarm optimization (PSO) algorithm and Gaussian process (GP) machine learning for back analysis is proposed. In order to reduce the cost of numerical calculation during displacement back analysis, the new method not only takes advantage of the global optimization performance of particle swarm optimization with quick convergence, but also uses GP model to summarize the historic experience during searching optimum solution and predicting the most perspective zone for guiding the flying of particle swarm. The results of performance analysis for different benchmark functions and application to a tunnel engineering show that the method is feasible to reduce remarkably computational time-consuming for solving problem of displacement back analysis based on numerical calculation.

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