平面应变条件下土体剪切带的产生条件与形成机理

基于通用有限元程序ABAQUS,利用修正剑桥模型分析正常固结土在平面应变条件下剪切带的产生条件和形成机理.研究表明,土的应变软化特性不是土体形成剪切带的必要条件;而试样端部摩擦约束与初始缺陷引起试样的不均匀受力,进而产生不均匀变形是剪切带产生的必要条件.提出剪切带形成的物理机制,即不均匀受力或缺陷单元引起土体的不均匀变形,使得某一剪切面上的单元首先达到临界承载能力,变形稍有增加,其他单元的应变能迅速释放,释放的应变能引起的冲击作用导致该截面上单元变形迅速增大、荷载降低,形成连续宏观的剪切带.

Production Conditions and Formation Mechanism of Shear Band Under Plane Strain Condition

Production conditions and formation mechanism of shear band were analyzed based on modified cam model in finite element program ABAQUS.The results show that strain softening is not the necessary condition of shear band formation in soil.Non-uniform force induced by end restraint and initial defect can cause non-uniform deformation,which is the necessary condition of shear band formation.The physical mechanism of shear band formation is presented that non-uniform force or defect element causes the non-uniform deformation in soil.If the critical bearing capacity of elements on some shear surface is reached,strain energy of other elements will rapidly release while deformation slightly increase.The impact action caused by strain energy releasing leads to rapid deformation increase and load reduction of elements on this section,and then continuous visible shear band is formed.