红粘土侧向卸荷真三轴试验及其力学特性分析  

Lateral unloading true triaxial test and analysis of mechanical properties for red clay

作　　者：周远忠[1,2,3] 刘新荣[1,2] 余瑜[1,2] 戴自然[3] 

机构地区：[1]重庆大学土木工程学院,重庆400045 [2]重庆大学山地城镇建设与新技术教育部重点实验室,重庆400045 [3]贵州师范大学材料与建筑工程学院,贵阳550001

出　　处：《重庆大学学报（自然科学版）》2014年第6期17-24,共8页Journal of Chongqing University

基　　金：国家自然科学基金资助项目(50334060);中央高校基本科研业务费科研专项基金资助项目(CDJZR12200018);贵州省联合科研基金资助项目(黔科合J字LKS[2013]38号)

摘　　要：采用刚柔复合型真三轴仪,模拟基坑实际开挖过程,进行了三向主应力不同的单面侧向卸荷真三轴试验,分析了侧向卸载和竖向加载条件下红粘土的应力应变关系、变形破损过程及其强度参数随基坑开挖的变化特点。根据红粘土强度参数在基坑开挖过程中的变化特点和工程实践确定强度折减系数,采用双强度折减法对土体强度参数进行分步折减,并选用FLAC3D程序和摩尔库伦模型对红粘土深基坑工程开挖的力学过程进行数值模拟。结果表明,加卸载条件下红粘土变形破损的力学机制完全不同,土体强度参数随基坑开挖深度的增大而减小,变化的范围、幅度和速度以递增方式变化。在相同竖向荷载条件下,开挖过程的土体较受压过程的土体更易变形破损而失稳。The actual excavation process of the deep foundation pit is simulated by single sided lateral unloading true triaxial test by using rigid-flexible compound true triaxial apparatus. The stress-strain relation,breakage process and change characteristics of the soil strength parameters are analyzed under lateral unloading and vertical loading conditions during the excavation of the pit. Then the reduction factor is determined according to the change characteristics of the red clay strength parameters during the excavation and experience in engineering practice. The soil strength parameters are reduced with double strength reduction methods step by step. The mechanical process for the excavation of the red clay pit is simulated by using FLAC3D procedures and Mohr-Coulomb model. The results show that the mechanical mechanism of the deformation and breakage process for red clay under lateral unloading condition iscompletely different from that of vertical loading. Soil strength parameters decrease while the depth of the excavation increases and the changes in range, magnitude and speed are changed incrementally. In the same vertical load condition, the soil under excavation condition is more deformable and easy to breakage compared to that under pressure conditions,which leads to the instability.

关 键 词：红粘土 侧向卸载作用 深基坑开挖 强度折减 数值模拟 

分 类 号：TU446[建筑科学—岩土工程]