Numerical investigations on mechanical characteristics and failure mechanism of outwash deposits based on random meso-structures using discrete element method  

作　　者：ZHANG Qiang XU Wei-ya LIU Qin-ya SHEN Jun-liang YAN Long 张强;徐卫亚;刘沁雅;沈俊良;闫龙

机构地区：[1]Key Laboratory of Geomechanics and Embankment Engineering of Ministry of Education(Hohai University) [2]Research Institute of Geotechnical Engineering, Hohai University [3]China Institute of Water Resources and Hydropower Research [4]Department of Physics, University of Toronto

出　　处：《Journal of Central South University》2017年第12期2894-2905,共12页中南大学学报（英文版）

基　　金：Project(2011CB013504) supported by the National Basic Research Program(973 Program)of China;Project(2013BAB06B01) supported by the National Science&Technology Pillar Program during the Twelfth Five-year Plan Period;Projects(11772118,51479049,51709282) supported by the National Natural Science Foundation of China;Project(2017M620838) supported by the Postdoctoral Science Foundation of China;Project(487237) supported by the Natural Sciences and Engineering Research Council of Canada

摘　　要：Outwash deposit is a unique type of geological materials, and its features such as heterogeneity, discontinuity and nonlinearity determine the complexity of mechanical characteristics and failure mechanism. In this work, random meso-structure of outwash deposits was constructed by the technique of computer random simulation based on characteristics of its meso-structure in the statistical sense and some simplifications, and a series of large direct shear tests on numerical samples of outwash deposits with stone contents of 15%, 30%, 45% and 60% were conducted using the discrete element method to further investigate its mechanical characteristics and failure mechanism under external load. The results show that the deformation characteristics and shear strength of outwash deposits are to some extent improved with the increase of stone content, and the shear stress–shear displacement curves of outwash deposits show great differences at the post-peak stage due to the random spatial distribution and content of stones. From the mesoscopic view, normal directions of contacts between "soil" and "stone" particles undergo apparent deflection as the shear displacement continues during the shearing process, accompanying redistribution of the magnitude of contact forces during the shearing process. For outwash deposits, the shear zone formed after shear failure is an irregular stripe due to the movements of stones near the shear zone, and it expands gradually with the increase of stone content. In addition, there is an approximately linear relation between the mean increment of internal friction angle and the stone content lying between 30% and 60%, and a concave nonlinear relation between the mean increment of cohesion and stone content, which are in good agreement with the existing research results.Outwash deposit is a unique type of geological materials, and its features such as heterogeneity, discontinuity and nonlinearity determine the complexity of mechanical characteristics and failure mechanism. In this work, random meso-structure of outwash deposits was constructed by the technique of computer random simulation based on characteristics of its meso-structure in the statistical sense and some simplifications, and a series of large direct shear tests on numerical samples of outwash deposits with stone contents of 15%, 30%, 45% and 60% were conducted using the discrete element method to further investigate its mechanical characteristics and failure mechanism under external load. The results show that the deformation characteristics and shear strength of outwash deposits are to some extent improved with the increase of stone content, and the shear stress–shear displacement curves of outwash deposits show great differences at the post-peak stage due to the random spatial distribution and content of stones. From the mesoscopic view, normal directions of contacts between "soil" and "stone" particles undergo apparent deflection as the shear displacement continues during the shearing process, accompanying redistribution of the magnitude of contact forces during the shearing process. For outwash deposits, the shear zone formed after shear failure is an irregular stripe due to the movements of stones near the shear zone, and it expands gradually with the increase of stone content. In addition, there is an approximately linear relation between the mean increment of internal friction angle and the stone content lying between 30% and 60%, and a concave nonlinear relation between the mean increment of cohesion and stone content, which are in good agreement with the existing research results.

关 键 词：outwash DEPOSITS RANDOM meso-structures DISCRETE ELEMENT method NUMERICAL tests mechanical characteristics FAILURE mechanism 

分 类 号：P642[天文地球—工程地质学] TU4[天文地球—地质矿产勘探]