结构性黄土的修正Duncan-Chang模型

Modified Duncan-Chang model of constitutive loess

为了实现原状湿陷性黄土结构性与其本构模型研究的统一,解决软化型应力-应变曲线的切线刚度矩阵正定性问题,通过研究原状结构性黄土在不同含水率和固结围压条件下由增湿、固结作用和剪切变形引起的结构性损伤规律,建立可以反映结构性变化的修正非线性Duncan-Chang模型.该模型考虑了增湿和加荷对土体结构的损伤破坏,把含水率作为一个重要的变量,用一族具有相同初始切线模量和不同极限强度的双曲线来求取当前应变状态处的切线模量,能够统一描述结构性黄土的应变软化和硬化型应力-应变关系曲线,形成解决原状湿陷性黄土增湿和应力耦合条件下变形及强度计算问题的新方法.

In order to realize the unification of investigation of structural feature of intact collapsible loess with that of constitutive model and solve the problem of positive definiteness of tangent stiffness matrix of softening stress-strain curves,the pattern of structural damage of intact structural loess caused by moistening consolidation and shearing deformation was investigated in the condition of different water content and consolidation pressure,and a modified Duncan-Chang constitutive model of collapse loess was established.In this nonlinear constitutive model,the damage of soil structure caused by moisture addition and load application was taken into consideration and the moisture content was taken as an important variable to calculate the tangent modulus of current strain state with a bunch of hyperbolas with identical initial tangent modulus and different ultimate strength.By so doing,the stress-strain curve of structural loess could be described in a unified way with the strain-induced hardening and softening,and a new method of deformation and strength calculation was formed for the case of intact collapsible loess with coupled moisture addition and stress changing.