复杂加载下K_(0)超固结黏土的本构模型  

Constitutive model for K_(0) overconsolidated clay under complex loading

作　　者：万征 曹伟 易海洋 WAN Zheng;CAO Wei;YI Haiyang(School of Architectural Engineering,North China Institute of Science and Technology,Langfang,Hebei 065201,China)

机构地区：[1]华北科技学院建筑工程学院,河北廊坊065201

出　　处：《岩石力学与工程学报》2022年第4期849-864,共16页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学青年基金(52004090);廊坊市科学技术研究与发展计划项目(2019013129)。

摘　　要：卸载后的K_(0)超固结黏土同时具有初始各向异性以及超固结特性,其特点有如下三方面:(1)当大主应力沿着K_(0)固结沉积面法线方向加载时,此时的剪切模量较等方向固结的剪切模量更高。(2)由于初始偏压固结导致三轴压缩下K_(0)固结黏土的临界状态应力比相较等方向固结的更大。(3)循环加载导致超固结特性以及应力诱导各向异性更为显著。基于超固结土UH模型,引入反映初始各向异性的边界面转轴参量ζ,通过倾斜边界面来提高其塑性模量。分析其剪胀应力比特征,提出状态应力比来替换统一硬化参数中的普通应力比,用来反映应变硬化、软化现象,引入旋转硬化规则用来反映复杂加载路径下的应力诱导各向异性性质,同时修正统一硬化参数,用来反映循环加载下的塑性体应变累积特性,塑性偏应变的滞回圈与棘轮特征,卸载路径的塑性变形特性。利用基于t准则的变换应力方法将上述新模型转变为三维本构模型,通过与一系列K;超固结黏土在不排水及循环加载等复杂加载路径下的试验与预测结果进行对比,结果表明:新模型可简单方便地应用于K_(0)超固结黏土在复杂加载路径下的应力-应变关系模拟中。After unloading,the K_(0) overconsolidated clay has both initial anisotropy and overconsolidation characteristics. Specifically,the characteristic of the K_(0) overconsolidated clay has the following three aspects:(1)When the major principal stress is loaded along the direction normal to the K_(0) consolidation deposition surface,the shear modulus is higher than that of the isotropic consolidation.(2) Due to the initial deviatoric consolidation,the critical state stress ratio of the K;consolidated clay under triaxial compression is larger than that of the isotropic consolidation.(3) Cyclic loading leads to more significant overconsolidation characteristics and stress-induced anisotropy. Based on the UH model of the overconsolidated clay,a rotational axis parameter ζ,reflecting the initial anisotropy of the boundary surface,is introduced to increase the plastic modulus of the overconsolidated clay by inclining the boundary surface. By analyzing the dilatancy characteristics of the stress ratio,the state stress ratio is proposed to replace the normal stress ratio in the unified hardening parameter for reflecting the phenomenon of strain hardening and softening. The introduction of the rotational hardening rule is used to reflect the stress-induced anisotropy under complex loading paths. The unified hardening parameter is modified to reflect the plastic volume strain accumulation characteristics under cyclic loading,hysteresis and ratchet characteristics of plastic deviatoric strain and plastic deformation characteristics of unloading path. Based on the stress transformation method of t criterion,the new model is converted into a three dimensional constitutive model. By comparing the test and prediction results for a series of K_(0) overconsolidated clays in the undrained loading and cyclic loading paths,it is revealed that the new model can be conveniently applied to model the stress-strain relationship for K;overconsolidated clay under complex loading paths.

关 键 词：土力学 各向异性 超固结黏土 剪胀 循环加载 滞回圈 

分 类 号：TU43[建筑科学—岩土工程]