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饱和砂土液化后大变形机制的离散元细观分析

DEM study of mechanism of large post-liquefaction deformation of saturated sand
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摘要 采用颗粒流软件模拟了饱和砂土在不排水条件下的循环剪切试验,研究了不同因素对液化的影响,并进一步分析了饱和砂土液化后宏观变形的基本规律。在此基础上,从孔隙分布角度解释了砂土液化后的大变形的细观物理机制。通过自编程序对颗粒排列和孔隙分布的演化过程进行定量描述,给出孔隙率标准差作为液化后体积收缩势的度量,并研究了孔隙率标准差与液化后大变形的关系。离散元细观数值模拟再现了室内试验中的宏观现象,证实了室内试验中饱和砂土液化后的有限剪切大变形是客观真实的材料响应。土体体积收缩势的累积所导致的孔隙均匀化以及土颗粒间自由空隙增大正是饱和砂土液化后循环剪应变逐渐增大的细观机制。孔隙率标准差作为孔隙均匀化的量化指标,与循环剪应变各周次幅值有良好的相关性。 The particle flow code(PFC)was adopted to simulate the cyclic shear test of saturated sand under undrained condition.The influence of different conditions of sand samples on liquefactions was studied.The meso-mechanism of the large limited post-liquefaction deformation was explained by pore distributions.A statistic code was developed to quantify the arrangement of particle and pore,and standard deviation of porosity was proposed to measure the post-liquefaction volume shrinkage potential.Then relationship between the standard deviation of porosity and the limited large post-liquefaction deformation was investigated.It was found that initial conditions have little effect on the ultimate state of post-liquefaction sample,while it only influences the cycle numbers of initial liquefaction.The large limited post-liquefaction deformation on saturated sand in laboratory test repetitively occurs during numerical simulations.The homogenization of pore and the increasement of distance between particles caused by the accumulation of sand volume shrinkage potential was the meso-mechanism of the generation of the large limited post-liquefaction deformation during cyclic shear.As a quantitative index of pore homogenization,standard deviation of porosity got a favorable correlation with the shear strain amplitude in each cycle.
作者 魏星 张昭 王刚 张建民 WEI Xing;ZHANG Zhao;WANG Gang;ZHANG Jian-min(School of Civil Engineering,Southwest Jiaotong University,Chengdu,Sichuan 610031,China;School of Civil Engineering,Chongqing University,Chongqing 400045,China;Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)
出处 《岩土力学》 EI CAS CSCD 北大核心 2019年第4期1596-1602,1625共8页 Rock and Soil Mechanics
基金 国家自然科学基金(No.51679016,No.41602286).
关键词 颗粒流方法 砂土液化 孔隙分布 液化后大变形 particle flow method sand liquefaction pore distribution large post-liquefaction deformation
作者简介 第一作者:魏星,女,1977年生,博士,副教授,主要从事岩土本构理论和数值计算方面的研究。E-mail:weixinghl@163.com.
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