李宝平　平高权　张玉　杨倩

摘 要：以原状黄土为研究对象，通过平面应变试验，研究冻融循环对原状黄土物理力学性质的影响。结果表明：随着冻融循环周期的增大，土样表面损伤越严重;在同含水率、同固结围压的条件下，原状黄土的偏应力轴向应变（σ1-σ3）-ε1曲线随着冻融循环次数的增大而逐渐减小，并且冻融循环对原状黄土（σ1-σ3）-ε1曲线的劣化作用随着含水率的增大而增大，随着固结围压的增大而减小;根据摩尔库伦强度准则，得出粘聚力和内摩擦角均随着含水率的增大呈线性减小，黏聚力随着冻融循环周期的增大呈指数减小，内摩擦角随着冻融循环周期的增大而减小，且在3°范围内变化。基于试验数据的合理性，拟合出原状黄土随冻融循环周期的劣化模型，该模型经试验验证可较好地描述原状黄土随冻融循环周期的劣化规律。

关键词：冻融循环;平面应变;冻融黄土;原状黄土;劣化模型

中图分类号：TU444   文献标志码：A   文章编号：2096-6717（2021）02-0041-08

Abstract： Taking undisturbed loess as the research object， the effects of freeze-thaw cycles on the physical and mechanical properties of undisturbed loess were studied through plane strain tests. The results show that： as the freeze-thaw cycle increases， the surface damage of the soil sample becomes more severe; under the conditions of the same moisture content and consolidation confining pressure， the partial stress-axial strain of the undisturbed loess （σ1-σ3）-ε1 curve gradually decreases with the increase of the number of freeze-thaw cycles， and the degradation of the original loess （σ1-σ3）-ε1 curve by the freeze-thaw cycle increases with the increase of the water content and with the consolidation. As the confining pressure increases， it decreases. According to the Mohr-Coulomb strength criterion， it is concluded that both the cohesive force and the internal friction angle show a similar linear decrease with the increased water content， and the cohesive decreases exponentially with the increase of the freeze-thaw cycle， and the internal friction angle decreases slightly with the increase of the freeze-thaw cycle， but the fluctuation within 3°. Based on the rationality of the test data， a degradation model of the undisturbed loess along with the freeze-thaw cycle is fitted， which can be used to well describe the degradation law of the undisturbed loess with the freeze-thaw cycle after the test validation.

Keywords：freeze-thaw cycle; plane strain; freeze-thaw loess; undisturbed loess; degradation model

凍土是特殊土体，可以分为瞬时冻土、季节性冻土以及多年冻土。冻土在中国西北地区分布广泛，主要为季节性冻土。随着中国西北地区的基础建设、高速公路和铁路网越来越密集，农业灌溉量增加，工程地质环境越来越脆弱，在此过程中，冻融病害引发的问题频发。在实际工程中，平面应变是土体经常受到的一种应力状态，如填方路基和基坑等都属于平面应变受力状态，而这些构筑物在运行中都会经受冻融循环作用[1]。……