低液限黏土应力松弛特性三轴试验研究

Triaxial Test Study on Stress Relaxation Behavior of Low Liquid Limit Clay

摘要

为探究土体流变特性,针对某覆盖层深部低液限黏土,进行了排水条件下的应力松弛三轴试验,研究了不同围压下黏土的应力松弛特性。分析发现:不同围压下初始阶段体变变化较快,但是整体的体变量较小;黏土应力松弛性质随围压的增大明显减弱;在半对数坐标系中,不同围压下应力松弛曲线的初始段并不符合直线关系,但经过一定时间后满足直线关系;基于试验结果进一步拓展了Lacerda和Houston的应力松弛经验公式;引入新的参数应力松弛率Q,发现不同围压下应力松弛率Q随时间延长先快速减小,而后逐渐趋于稳定。基于此,建立了应力松弛率与围压和时间的经验关系式,揭示了应力随时间松弛的规律;基于体变结果,建立了应力松弛条件下体变随围压和时间变化的关系,为推广建立相关流变模型提供可能。

Abstract

Stress relaxation is one of the typical manifestations of soil rheology. For further investigation, drained triaxial stress relaxation tests were carried out on deep low liquid limit clay from an overburden layer, and the stress relaxation characteristics of the clay under different confining pressures were studied. It was found that the initial volume change was rapid under different confining pressures, but the overall volume change was small. The stress relaxation property of the clay decreased significantly with the increase of the confining pressures. In the coordinate system with time on the logarithmic axis, the initial section of the stress relaxation curves under different confining pressures did not follow a linear relationship, but did after a certain period of time. The empirical formulae for the stress relaxation proposed by Lacerda and Houston was further extended based on the test results. A new parameter Q was introduced and defined as the stress relaxation rate, and it was found that the stress relaxation rate Q under different confining pressures decreased rapidly with time and then gradually tended to be stable. Based on this, an empirical equation associated with the stress relaxation rate, confining pressure and time is established, which reveals the law of stress relaxation with time. Based on the volume change results, the relationship of volume change with confining pressure and time under stress relaxation conditions is established, which provides a basis for the generalization and establishment of relevant rheological models.

关键词

三轴试验 / 黏土 / 流变特性 / 应力松弛

Key words

triaxial test / clay / rheological behavior / stress relaxation

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基金资助

国家自然科学基金重点项目(U2040221)

华能集团总部科技项目(HNKJ20-H45)

水利部堤防安全与病害防治工程技术研究中心开放课题基金资助项目(LSDP202305)