砂土特征状态线及不排水特性的初始状态分区

Characteristic state lines and subarea of initial state of sand under undrained shearing

砂土不排水特性表现出强烈的初始状态依赖性,为深入探究砂土这一特性,介绍了e-lnp(e为孔隙比,p为围压)平面内砂土已有与不排水特性有关的初始状态特征线,即最松固结线(loosest consolidation line,简称LCL)、静态液化分界线(static liquefaction dividing line,简称LDL)以及准稳态分界线(quasi steady-state dividing line,简称QDL),并在引入砂土正常压缩线(normal compression line,简称NCL)的基础上,结合剪胀和屈服理论,补充论证了LDL的存在性,给出了QDL的简易确定方法。基于特征状态线,将砂土初始状态进行了分区,分别为Ⅰ静态液化区、Ⅱ应变软化区、Ⅲ准稳态区、Ⅳ应变硬化区,使得砂土在同一初始状态特征区表现出相似的不排水剪切特性。分析了初始状态分区的应用,包括理论应用与工程应用,以期为砂土不排水特性初始状态依赖性的理解及相关工程实际提供指导。

The undrained behavior of sand is mainly dependent on its initial state.To better understand and reveal this feature,the characteristic state lines,namely the loosest consolidation line(LCL),the static liquefaction dividing line(LDL)and the quasi steady-state dividing line(QDL),which are related to the undrained behavior of sand in the e-lnp plane,are presented firstly.Based on the theory of shear yielding and dilatancy,a simple method used to determine QDL is given,and the existence of LDL is demonstrated by introducing the normal compression line(NCL)of sand.Subsequently,the initial state of sand is divided into four characteristic subareas,which can be referred to as the static liquefaction subarea Ⅰ,the strain softening subarea Ⅱ,the quasi-steady state subarea Ⅲ and the strain hardening subarea Ⅳ,and sand shows the similar undrained behavior when its initial state places in the individual subarea.Finally,the theoretical and engineering applications of subarea are analyzed.