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Numerical computation of anti-liquefaction effect of lattice-type cement-mixed soil countermeasure

Journal of Central South University 2008年第S2期15卷 155-160页

作者：高玉峰杨雪玲沈扬周源 key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai University geotechnical Research Institute Hohai University East China Electric Power Design geotechnical engineering Company

Continuous soil-cement wall confinement method to resist liquefaction is a new kind of process. However, whether it also has a good effect on anti-liquefaction or not needs to be urgently answered for earthquake engineering. Quiet boundary is adopted on the lateral face while free field boundary is employed at the bottom. Byrne model on dynamic pore water pressure generation is accepted and natural seismic wave EI Centro whose peak acceleration is adjusted to 0.2 g in proportion is used for input. A double-layer foundation with sandy soil in the upper portion while clay soil in the lower part is chosen as the calculation model, which is 30 m in length and 20 m in width. The groundwater level is on the ground surface. Excess pore water pressure rate is considered as a liquefaction index in the three-dimensional non-linear earthquake response computation. The anti-liquefaction effectiveness and its influencing factors, such as confinement element area are studied. For the natural double-layer foundation, it is liquefied when the excess pore water pressure rate reaches 1.0 under the seismic load. Under the same earthquake load, the peak excess pore water pressure reduces to 0.56 after adopting reinforcement of the continuous soil-cement wall, which is 46% lower than before. It indicates that continuous soil-cement wall confinement method can attain the purpose of anti-liquefaction. Accordingly, it can be a sort of engineering measure to carry on the anti-liquefaction foundation treatment.

关键词： lattice-type cement-mixed soil countermeasure anti-liquefaction excess pore pressure ratio the smallest lattice area

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An anisotropic constitutive model of geomaterials based on true triaxial testing and its application

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Journal of Central South University 2017年第6期24卷 1430-1442页

作者： ZHANG Kun-yong Frederick Nai Charkley key laboratory of Ministry of Education for geomechanics and Embankment engineering Nanjing 210098China geotechnical Research Institute Hohai UniversityNanjing 210098China

Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus. The loads were applied from the major principal and minor principal directions, respectively, to simulate the construction and water impounding process of a rock fill dam. The stress and strain relationships induced by the different loading methods were investigated. A remarkable stress-induced anisotropy under complex stress state was observed. Contrary to popular assumptions in traditional numerical analysis and constitutive models, it was found that different elastic modulus and Poisson ratio exist in different principal directions in rock fill dams. From the testing results, an anisotropic constitutive model based on Duncan-Chang nonlinear model is presented to overcome the limitations of axi-symmetric assumptions in conventional triaxial experiments and constitutive models. Both models were then applied in FEM analysis of an under-construction earth core high rock soil filled dam with the focus on hydraulic fracturing. The study reveals the major biases that exist when numerical analysis and constitutive models do not give serious consideration to the intermediate principal stress and anisotropy effects in soil rock built structures.

关键词： true triaxial test stress induced anisotropy constitutive model complex stress state finite element method (FEM)

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UNCERTAINTY ANALYSIS OF ROCK FAILURE BEHAVIOUR USING AN INTEGRATION OF THE PROBABILISTIC COLLOCATION METHOD AND ELASTO-PLASTIC CELLULAR AUTOMATON

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Acta Mechanica Solida Sinica 2015年第5期28卷 536-555页

作者： Pengzhi Pan Fangsheng Su Haijun Chen Shilin Yan Xiating Feng Fei Yan State key laboratory of geomechanics and geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences School of Science Wuhan University of Technology

The Karhunen-Loeve （KL） expansion and probabilistic collocation method （PCM） are combined and applied to an uncertainty analysis of rock failure behavior by integrating a self- developed numerical method （i.e., the elastic-plastic cellular automaton （EPCA））. The results from the method developed are compared using the Monte Carlo Simulation （MCS） method. It is concluded that the method developed requires fewer collocations than MCS method to obtain very high accuracy and greatly reduces the computational cost. Based on the method, the elasto- plastic and elasto-brittle-plastic analyses of rocks under mechanical loadings are conducted to study the uncertainty in heterogeneous rock failure behaviour.

关键词： uncertainty analysis probabilistic collocation method elasto-plastic cellular au-tomaton Karhunen-Loeve expansion rock failure process PCM-EPCA

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Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form

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Journal of Central South University 2016年第4期23卷 898-905页

作者：王辉陈卫忠王清标郑朋强 Department of Resources and Civil engineering Shandong University of Science and Technology geotechnical & Structural engineering Research Center Shandong University State key laboratory of geomechanics and geotechnical engineering (Institute of Rock and Soil Mechanics Chinese Academy of Sciences)

Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.

关键词： rheological test constitutive model staged optimization analysis reasonable support form

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Numerical Analysis and Centrifuge Modeling of Shallow Foundations

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China Ocean engineering 2014年第2期28卷 163-180页

作者：罗强栾茂田杨蕴明王忠涛赵守正 Institute of geotechnical engineering School of Civil EngineeringDalian University of Technology Academy of Civil engineering and Architecture Nanyang Normal University State key laboratory of geomechanics and geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.

关键词： non-coaxial model strain softening FEM analysis centrifuge test shallow foundation

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An analytical solution to the scattering of cylindrical SH waves by a partially filled semi-circular alluvial valley: near-source site effects

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Earthquake engineering and engineering Vibration 2015年第2期14卷 189-201页

作者： Zhang Ning Gao Yufeng Yang Jie Xu Changjie geotechnical Research Institute Hohai University key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai University Nanjing Hydraulic Research Institute Research Center of Coastal and Urban geotechnical engineering Zhejiang University

The earth’s surface irregularities can substantially affect seismic waves and induce amplifi cations of ground motions. This study investigates whether and how the source characteristics affect the site amplifi cation effects. An analytical model of a line source of cylindrical waves impinging on an alluvial valley is proposed to link the source and site. The analytical solution to this problem proves one aspect of the strong effect of source on site amplifi cation, i.e., the wave curvature effect. It is found that the site amplifi cation depends on the source location, especially under conditions of a small source-to-site distance. Whether the displacement is amplifi ed or reduced and the size of the amplifi cation or reduction may be determined by the location of the source. It is suggested that traditional studies of site responses, which usually ignore the source effect, should be further improved by combining the source with site effects.

关键词： site effects source effects wave function expansio

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An improved three-dimensional spherical DDA model for simulating rock failure

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Science China(Technological Sciences) 2015年第9期58卷 1533-1541页

作者： JIAO YuYong HUANG GangHai ZHAO ZhiYe ZHENG Fei WANG Long State key laboratory of geomechanics and geotechnical engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences School of Civil and Environmental engineering Nanyang Technological University

In this paper, a discontinuous numerical model, namely SDDARF3D(three-dimensional spherical discontinuous deformation analysis for rock failure), is proposed for simulating the whole process of rock failure. Firstly, within the framework of the classical discontinuous deformation analysis(DDA) method, the formulation of three-dimensional spherical DDA(3D SDDA) is deduced; secondly, a bonding and cracking algorithm is constructed and the SDDARF3 D model is proposed; thirdly, corresponding VC++ calculation code is developed and some verification examples are calculated. The simulated results can intuitively reproduce the failure phenomena of rock mass, indicating that the proposed SDDARF3 D numerical model is correct and effective.

关键词： rock failure three-dimensional spherical discontinuous deformation analysis crack propagation bonding and cracking algorithm

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THEORETICAL MODEL OF EFFECTIVE STRESS COEFFICIENT FOR ROCK/SOIL-LIKE POROUS MATERIALS

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Acta Mechanica Solida Sinica 2009年第3期22卷 251-260页

作者： Kai Zhang Hui Zhou Dawei Hu Yang Zhao Xiating Feng State key laboratory of geomechanics and geotechnical engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China

Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.

关键词： rock/soil-like porous materials generalized model for effective stress coefficient tensor equivalent connectivity index of pore genetic algorithm

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Resistivity characteristics of red clay contaminated by Cu2+

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Yantu Lixue/Rock and Soil Mechanics 2020年 41卷 200-208页

作者： Chen, Yi-Cheng Song, Yu Chen, Xue-Jun Bi, Peng-Yan Huang, Xiang Liang, De-Xian Guilin University of Technology Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering Guilin 541004 China

The resistivity of red clay contaminated by Cu2+ was studied in the improved Miller Soil Box under the consideration of different moisture content, porosity and pollution concentration. The comparison of resistivity measurement results between two-electrode and four electrode methods is studied, and the influence of potential electrode penetrations in four electrode method is also investigated. The order of impact degree of three main factors (moisture content, porosity and pollution concentration) on the resistivity of soil polluted by heavy metals were qualitatively and quantitatively analyzed by the orthogonal tests. Besides, a resistivity prediction model for heavy metal contaminated red clay based on these three major impact factors was established. The results show that the four electrode method should be used and the ideal penetration depth of potential electrode is 3 cm in the measurement of soil resistivity. The order of impact degree is Cu2+ concentration > moisture content > porosity. The relationship between resistivity and these three factors can be expressed using a series of power functions. The resistivity of red clay contaminated by heavy metals decreases with the increase of Cu2+ concentration and moisture content, and increases with the increase of porosity. The calculated values based on the resistivity prediction model of heavy metal contaminated red clay under these three main factors show a good agreement with the measured values. The method can be effectively applied in the evaluation of heavy metal contaminated sites in red clay areas. © 2020, Science Press. All right reserved.

关键词： Heavy metals

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MESHLESS METHOD OF DUAL RECIPROCITY HYBRID RADIAL BOUNDARY NODE METHOD FOR ELASTICITY

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Acta Mechanica Solida Sinica 2010年第5期23卷 447-458页

作者： Fei Yan Xiating Feng Hui Zhou 1(State key laboratory of geomechanics and geotechnical engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Science,Wuhan 430071,China) [a] State key laboratory of geomechanics geotechnical engineering Institute of Rock Soil Mechanics Chinese Academy of Science Wuhan 430071 China

Combining the radial point interpolation method （RPIM）, the dual reciprocity method （DRM） and the hybrid boundary node method （HBNM）, a dual reciprocity hybrid radial boundary node method （DHRBNM） is proposed for linear elasticity. Compared to DHBNM, RPIM is exploited to replace the moving least square （MLS） in DHRBNM, and it gets rid of the deficiency of MLS approximation, in which shape functions lack the delta function property, the boundary condition can not be applied easily and directly and it＇s computational expense is high. Besides, different approximate functions are discussed in DRM to get the interpolation property, in which the accuracy and efficiency for different basis functions are compared. Then RPIM is also applied in DRM to replace the conical function interpolation, which can greatly improve the accuracy of the present method. To demonstrate the effectiveness of the present method, DHBNM is applied for comparison, and some numerical examples of 2-D elasticity problems show that the present method is much more effective than DHBNM.

关键词： meshless method hybrid boundary node method dual reciprocity method radial point interpolation method elasticity

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