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不同含石量下泥岩土石混合体剪切特性及细观破坏机制
张敏超1,2, 刘新荣1,2, 王鹏1,2, 杜立兵1,2
1.重庆大学 土木工程学院;2.山地城镇建设与新技术教育部重点实验室, 重庆 400045
摘要:
为探究含石量对泥岩土石混合体剪切特性及细观破坏机制的影响,设计了含石量20%~80%共4组试样,分别在0.2、0.4、0.6、0.8 MPa这4种不同围压下进行室内大型三轴剪切试验,研究不同含石量试样的偏应力、体积应变及抗剪强度参数的变化规律;基于数字图像处理技术生成PFC2D颗粒流数值模型进行一系列数值分析。结果表明:试样抗剪强度随含石量增大而不断增大。与其他类型的土石混合体不同的是,泥岩土石混合体在低围压下呈先剪缩后剪胀的变化规律,且含石量越高,最终剪胀效果越明显;在高围压下始终表现为剪缩,且含石量越低,剪缩效果越强。内摩擦角随含石量增大呈慢快慢的“S”型增长趋势,且在20%~80%含石量内增长较快;黏聚力随含石量增大不断降低,但下降速率逐渐减小。数值试验表明:土石混合体在剪切过程中存在拉剪混合破坏;随含石量增加,土石混合体骨架结构效应越来越显著,剪切带绕过块石,形成多个形状不规则的小剪切带。
关键词:  含石量  泥岩土石混合体  颗粒流模型  剪切特性  细观破坏机制
DOI:10.11835/j.issn.2096-6717.2019.116
分类号:TU411
基金项目:国家自然科学基金(No.41772319)
Shear properties and failure meso-mechanism of soil-rock mixture composed of mudstone under different rock block proportions
Zhang Minchao1,2, Liu Xinrong1,2, Wang Peng1,2, Du Libing1,2
1.School of Civil Engineering;2.Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing University, Chongqing 400045, P. R. China
Abstract:
To investigate the impact of rock block proportion (RBP) on shear properties and meso-failure mechanism of mudstone soil-rock mixture (SRM). Four groups of sample with RBP ranging from 0% to 80% were prepared for large-scale triaxial tests under three different confining pressures (0.2、0.4、0.6、0.8 MPa). and the change rules of deviatoric stress、volumetric strain and shear strength of sample with different RBPS. Then, a series of numerical analysis were conducted based on particle flow numerical method PFC2D by digital image processing. It is shown that the shear strength increases with the increase of RBP. Unlike other types of soil-rock mixture, sample shows the law of shearing contraction and then dilatation under low confining pressure, and the stronger the final shear dilatation with the higher RBP. The shear contraction decreases under high confining pressure, and the stronger the final shear contraction with lower RBP. With the increase of SRM, the internal friction angle shows slow-fast-slow and "S" growth trend and growth faster between 20%~80% RBP. The cohesion decreases all the time, but the rate of decline is decreasing. Numerical tests indicate that the failure of SRM is tension-shear mixing failure during shear tests. The skeleton-effect of rock blocks becomes more and more obvious with the increase of SRM, the shear zone bypassing the rock blocks and multiple irregular and small shear zone is formed.
Key words:  rock block proportion  mudstone soli-rock mixture  particle flow model  shear properties  meso-failure mechanism
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