考虑中主应力影响的黄土强度和变形特性研究

Study on strength and deformation characteristics of loess by considering the influence of intermediate principal stress

为研究考虑中主应力影响下黄土的强度和变形特性,利用西安理工大学新型真三轴仪开展天然黄土的真三轴固结排水试验,根据原状黄土在不同固结围压和不同中主应力比条件下的应力-应变关系曲线,探讨破坏时应力不变量与平均主应力以及大主应力与中主应力的关系,在此基础上对比分析不同强度准则得到的考虑中主应力影响的强度参数,结果表明Matsuoka-Nakai(SMP)准则能更好地描述中主应力影响下的黄土实际强度特性。进而,考虑到工程界应用最为广泛的非线性模型邓肯-张模型未考虑中主应力影响的局限性,本文通过基于广义胡克定律及Matsuoka-Nakai(SMP)准则分别对E-B模型中初始弹性模量和破坏比参数进行了修正,提出了一个考虑中主应力影响的变形模量修正方法,该方法可为邓肯-张模型在复杂应力情况下的应用提供借鉴,对于描述原状黄土强度和变形规律的研究具有参考意义。

In order to study the strength and deformation characteristics of loess under complex stress paths,the true triaxial consolidation and drainage tests of natural loess were carried out by the true triaxial apparatus in Xi'an University of Technology.According to the stress-strain relationship curves of undisturbed loess under different consolidation confining pressures and different medium principal stress ratios,the relationship between stress invariants and average principal stress and between large principal stress and medium principal stress during failure was discussed,and on the basis,the strength parameters considering the influence of intermediate principal stresses obtained by different strength criteria were compared and analyzed.The results show that the Matsuoka-Nakai(SMP)criterion can better describe the actual strength characteristics of loess under the influence of intermediate principal stresses.Then,the limitation that the Duncan-Chang model,which is the most widely used nonlinear model in engineering,does not consider the influence of intermediate principal stress is emphasized.In this work,based on the generalized Hooke's law and the Matsuoka Nakai(SMP)criterion,the initial elastic modulus and the failure ratio parameters are modified,respectively,and a correction method of deformation modulus considering the influence of intermediate principal stress is proposed,which provides reference for the application of Duncan-Chang model under complex stress conditions,and has practical reference significance for the study of strength and deformation law of undisturbed loess.