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Probabilistic analysis of random contact force between geomembrane and granular material

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Journal of Central South University 2014年第8期21卷 3309-3315页

作者：姜晓桢束一鸣 College of Water Conservancy and Hydropower Engineering Hohai University Department of Geotechnical Engineering Nanjing Hydraulic Research institute

A probabilistic method based on principle of maximum entropy was employed to analyze the randomness of contact force between geomembrane and granular *** contact force distribution is exponential according to the proposed method and the grain size is the most important factor that affects the distribution of contact *** proposed method is then verified by a series of laboratory experiments using glass beads and cobbles as granular material and a very thin pressure,indicating that film is firstly used in these experiments which give a reliable method to measure the contact force at each contact point.

关键词： geomembrane granular material contact force probability density function

Stress and fabric in granular material

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Theoretical & Applied Mechanics Letters 2013年第2期3卷 10-15页

作者： Ching S. Chang Yang Liu Department of Civil Engineering University of Massachusetts Amherst Department of Civil Engineering University of Science and TechnologyBeijing

It has been well recognized that, due to anisotropic packing structure of granular material, the true stress in a specimen is different from the applied stress. However, very few research efforts have been focused on quantifying the relationship between the true stress and applied stress. In this paper, we derive an explicit relationship among applied stress tensor, material-fabric tensor, and force-fabric tensor; and we propose a relationship between the true stress tensor and the applied stress tensor. The validity of this derived relationship is examined by using the discrete element simulation results for granular material under biaxial and triaxial loading con- ditions.

关键词： stress tensor force fabric tensor material fabric tensor granular material discrete elementmethod

Numerical implementation of suction-dependent resilient modulus constitutive model for subgrade granular material

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Journal of Southeast University(English Edition) 2018年第2期34卷 251-258页

作者： Liao Gongyun Chen Huaqing Sun Peixiang School of Transportation Southeast UniversityNanjing 210096China

In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient modulus model was integrated into the commercial finite element(FE)code Abaqus by developing a user-defined material(UMAT)*** developed model was validated by triaxial test results under different suction conditions and good agreement was achieved.A three-dimensional(3D)FE pavement model was established and the suction-dependent properties of subgrade granular material was characterized by the developed constitutive ***-mechanical pavement responses subjected to three moisture states and the falling weight deflectometer(FWD)load were *** results reveal that the resilient modulus of subgrade granular material is sensitive to suction and stress states;high groundwater table decreases the overall resilient moduli of subgrade structure due to suction reduction,leading to the increase of the maximum surface deflection,the tensile strain at bottom of the surface layer,compressive strain on top of subgrade,and consequently,deterioration in pavement performance.

关键词： resilient modulus model suction pavement model finite element granular material

The material Deformation and Internal Structure Development of granular materials under Different Cyclic Loadings

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Computer Modeling in Engineering & Sciences 2022年第2期130卷 653-670页

作者： Jiao Wang Xihua Chu Jinbao Wang School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu610031China Department of Engineering Mechanics Wuhan UniversityWuhan430072China School of Marine Engineering Equipment Zhejiang Ocean UniversityZhoushan326022 China

Common structures in engineering such as slopes,roadbeds,ballasts,etc.,are closely related to granular *** are usually subjected to long-term cyclic *** study mainly focused on the mechanical behaviors of randomly arranged granular materials before they reach a stable state under different cyclic *** variation of the maximum axial strain and the influence of CSR(cyclic stress ratio)were *** energy consumed in each cycle under constant confining stress loading condition is significantly greater than that of the fixed wall loading *** internal deformation evolution of granular materials is studied in *** deformation mode of granular material under cyclic loading at different positions inside the material is different according to the strain *** addition,the strain,force chain structure and contact force magnitude are combined to explore their effects on local deformation of granular materials under cyclic *** the perspective of the deformation form,the material sample can be divided into several regions,and the ability to adjust particle positions determines the deformation mode of different *** changes of local strain with the cyclic loading also reflect the contribution of particle displacements to the evolution *** research will provide insights into the understanding of granular materials behaviors under cyclic loading.

关键词： granular material DEM cyclic loading mesostructured force chain

Constitutive modelling of idealised granular materials using machine learning method

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第4期15卷 1038-1051页

作者： Mengmeng Wu Zhangqi Xia Jianfeng Wang Department of Architecture and Civil Engineering City University of Hong KongHong KongChina Shenzhen Research Institute of City University of Hong Kong ShenzhenChina

Predicting the constitutive response of granular soils is a fundamental goal in *** paper presents a machine learning(ML)framework for the prediction of the stress-strain behaviour and shearinduced contact fabric evolution of an idealised granular material subject to triaxial *** MLbased framework is comprised of a set of mini-triaxial tests which provide a benchmark for the setup and validation of the discrete element method(DEM)model of the granular materials,a parametric DEM simulation programme of virtual triaxial tests which provides datasets of micro-and macro-mechanical information,as well as a multi-layer perceptron(MLP)neural network which is trained and tested using the DEM-based *** ML model only requires the initial void ratio of the granular sample as the input for predicting its constitutive *** excellent agreement between the ML model prediction and experimental test and DEM simulation results indicates that the MLebased modelling approach is capable of capturing accurately the effects of initial void ratio on the constitutive behaviour of idealised granular materials,bypassing the need to incorporate the complex micromechanics underlying the macroscopic mechanical behaviour of granular ***,a detailed comparison between the used MLP model and long short-term memory(LSTM)model was made from the perspective of technical algorithm,prediction accuracy,and computational efficiency.

关键词： Machine learning(ML) Multi-layer perceptron(MLP) Contact fabric granular material Discrete element method(DEM)

THE COMPACTION OF TIME-DEPENDENT VISCOUS granular materialS CONSIDERING INERTIAL FORCES

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Acta Mechanica Solida Sinica 2011年第6期24卷 495-505页

作者： Yuching Wu Jianzhuang Xiao Cimian Zhu Department of Building Engineering College of Civil Engineering Tongji University Shanghai 200092 China

In the present paper, compactions of time-dependent viscous granular materials are simulated step by step using the automatic adaptive mesh generation schemes. Inertial forces of the viscous incompressible aggregates axe taken into account. The corresponding conservation equations, the weighted-integral formulations, and penalty finite element model are investigated. The fully discrete finite element equations for the simulation are derived. Polygonal particles of aggregates are simplified as mixed three-node and four-node elements. The automatic adaptive mesh generation schemes include contact detection algorithms, and mesh upgrade schemes. Solu- tions of the numerical simulation axe in good agreement with some results from literatures. With minor modification, the proposed numerical model can be applied in several industries, including the pharmaceutical, ceramic, food, and household product manufacturing.

关键词： granular material automatic adaptive mesh generation finite element method,time-dependent aggregates

Computational multiscale methods for granular materials

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Theoretical & Applied Mechanics Letters 2013年第1期3卷 1-10页

作者： Xikui Li Yuanbo Liang Youyao Du Ke Wan Qinglin Duan The State Key Laboratory for Structural Analysis of Industrial Equipment Dalian University of Technology

The fine-scale heterogeneity of granular material is characterized by its polydisperse microstructure with randomness and no periodicity. To predict the mechanical response of the material as the microstructure evolves, it is demonstrated to develop computational multiscale methods using discrete particle assembly-Cosserat continuum modeling in micro- and macro- scales,respectively. The computational homogenization method and the bridge scale method along the concurrent scale linking approach are briefly introduced. Based on the weak form of the Hu-Washizu variational principle, the mixed finite element procedure of gradient Cosserat continuum in the frame of the second-order homogenization scheme is developed. The meso-mechanically informed anisotropic damage of effective Cosserat continuum is characterized and identified and the microscopic mechanisms of macroscopic damage phenomenon are revealed. c 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi： 10.1063/2.1301101]

关键词： granular material discrete particle assembly gradient Cosserat continuum computational homogenization bridge scale method damage characterization

Development of a constitutive model for rockfills and similar granular materials based on the disturbed state concept

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Frontiers of Structural and Civil Engineering 2012年第4期6卷 365-378页

作者： Mehdi VEISKARAMI Ali GHORBANI Mohammadreza ALAVIPOUR Department of the Civil Engineering The University of GuilanRashtIran

Behavior of rockfills was investigated experimentally and theoretically.A series of standard triaxial compression tests were carried out on a quarried rockfill material at different stress *** was found that both the stress level and the shear stress ratio,like most of granular materials,controls the behavior of rockfill *** lower shear stress ratios the behavior is much more similar to a nonlinear elastic *** the shear stress goes further,the stressstrain curve shows an elasto-plastic behavior which suggests using the disturbed state concept to develop a constitutive model to predict the stress-strain *** presented constitutive model complies reasonably with the experimental data.

关键词： constitutive model granular material rockfill plasticity disturbed state concept stress level

Investigation on relations between grain crushing amount and void ratio change of granular materials in one-dimensional compression and creep tests

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Journal of Rock Mechanics and Geotechnical Engineering 2011年第S1期3卷 415-420页

作者： Ron.C.K.Wong Department of Civil Engineering University of Calgary

Grain crushing plays an important role in one-dimensional (1D) compression and creep behaviors of granular materials under high stress. It is clear that the macro-properties of granular materials are closely related to the micro-fracture properties of grains in 1D compression and creep tests. In this paper, a series of 1D compression and creep tests were performed on Ottawa sand to investigate the deformation and grain crushing properties of granular materials, and it shows that the void ratio is correlated to the grain crushing amount (the quantity of crushed grains) for granular materials subjected to grain crushing. The test results, combining with the existing test data related to grain crushing of granular materials, were used to verify the relation. Moreover, the implications of these relations on the yield of granular material, and the equivalent effect of stress and time in changing soil fabric are presented.

关键词： granular material grain crushing geometrical aspect one-dimensional (1D) compression and creep yield soil fabric