重塑黏土真三轴试验强度特性及本构模型研究

土体的强度特性是岩土工程稳定性分析的重要依据。本文分析了不同含水率重塑粘土在复杂应力路径下的强度变化规律,获得以下主要结论:含水率较小时重塑粘土的应力应变曲线呈强硬化型,含水率较大时呈弱硬化型,含水率一定时随着中主应力比的增加应力应变曲线向外扩张;重塑粘土强度随着中主应力比的增加而增大,中主应力比小于0.5时增幅较大,大于0.5时增幅有所减小;不同含水率下重塑粘土强度在π平面上的破坏线为一族相似曲线,随着含水率的减小破坏线向外扩张且圆润度增强,破坏曲线的形态逐渐接近加权双剪强度理论。鉴于考虑轴对称应力条件下的邓肯-张模型不能反映中主应力变化的影响,通过重塑粘土的真三轴试验结果结合邓肯-张双曲模型建立了能够考虑中主应力比的改进邓肯-张模型,并与复杂应力路径的试验结果进行比较,验证了改进邓肯-张模型的有效性。

Experimental Investigation on Strength and Constitutive Model of Remolded Clay under True Triaxial Test

Strength characteristics of soil is an important basis for the stability analysis of Geotechnical engineering. The paper analyzed strength characteristics of remolded clay under different moisture content and complex stress path, obtaining the following main researches conclusions: the stress-strain curves of remolded clay show stronger hardening type under lower moisture content and weaker hardening type under higher moisture content. The stress-strain curve of remolded clay outwardly expands with the increasing of the ratio of intermediate principal stress when moisture content is constant. The strength of remolded clay increases with the increasing of intermediate principal stress ratio, and the rate of increase is larger when intermediate principal stress ratio is less than 0.5, while the rate of increase is smaller when greater than 0.5. The strength failure curves of remolded clay in the π plane are a family of similar curves under different moisture content, and the failure curves outwardly expands and its smooth degree increases with the decreasing of moisture content, whose shape gradually approachs the weighted twin shear strength theory. In view of the fact that the Duncan-Chang model under the axial symmetry stress did not reflect the influence of intermediate principal stress changes, through the results of true triaxial experimental and the Duncan-Chang hyperbolic model, the improved Duncan-Chang model considering the intermediate principal ratio was established. The experimental results under the complex stress path verify the validity of the improved Duncan-Chang model.