描述饱和黏性土应变软化的弹塑性双面模型  

Elastoplastic two-surface model for describing strain-softening behavior of saturated cohesive soils

作　　者：张涛[1] 李涛[1] 冯硕 ZHANG Tao;LI Tao;FENG Shuo(School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China)

机构地区：[1]北京交通大学土木建筑工程学院,北京100044

出　　处：《岩土力学》2022年第10期2757-2767,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金面上项目(No.51878035)。

摘　　要：常规三轴压缩试验中具有较强结构性的黏性土在围压较低时其应力-应变关系会呈现应变软化现象,一般还伴有塑性变形,通常土体内部结构损伤是应变软化产生的主要原因。考虑到采用经典塑性理论描述材料的应变软化不仅会违背Drucker的稳定性假设,而且也不能描述卸载塑性。因此,基于修正剑桥模型及Li和Meissner提出的塑性硬化准则,建立了一个描述饱和黏性土不排水应变软化的弹塑性双面模型。该模型以应力-应变曲线的峰值点分界,将应变硬化和应变软化分别作为独立的加载事件进行分析,同时引入新的结构性参数表征剪切过程中土体结构损伤导致的塑性刚度衰退。对不同固结状态饱和结构性黏土的三轴固结不排水压缩试验结果的模拟表明,所建模型能够较好地描述饱和黏性土的不排水应变软化特性。In the conventional triaxial compression test,the stress-strain relationship of strong structured cohesive soils under a low confining pressure will show strain softening and is usually accompanied by plastic deformation.Generally,the internal structure damage of soil is the main cause of strain softening.Using classical plastic theory to describe the strain softening characteristics of materials may violate the Drucker’s stability hypothesis,and cannot describe the plastic deformation during unloading.Based on the modified Cam-clay model and the plastic hardening rule proposed by Li and Meissner,an elastoplastic two-surface model is established.This model divides the stress-strain curve into strain hardening stage and strain softening stage at the peak stress point and the divided two stages are analyzed as independent loading events respectively.Meanwhile,a new structural parameter is proposed to characterize the degradation of plastic stiffness caused by soil structure damage during loading.Additionally,the comparisons between simulated and measured results of saturated structural clay in different consolidation states indicate that the model can describe the stress-strain curves and stress path curves with high accuracy and can give reasonable and good simulations of strain softening of structured clays in undrained condition.

关 键 词：结构性土 应变软化 塑性硬化准则 弹塑性模型 不排水剪切 

分 类 号：TU442[建筑科学—岩土工程]