冻融循环对原状黄土的持水特性影响

Water retention behaviours of intact loess exposed to freeze-thaw cycles

冻融作用是引起黄土边坡溜塌和路基沉陷等工程病害不可忽视的重要因素。持水特性作为分析非饱和黄土水力-力学特性的关键物性,有关冻融作用对黄土持水特性的影响有待深入研究。该文以冻融循环后原状黄土为研究对象,研究了冻融循环次数和冻融前含水率对持水曲线及其特征参数的影响。研究结果表明,冻融循环对持水曲线的影响呈波动性变化,影响程度受控于循环次数与冻融前初始含水率水平;不同冻融条件下饱和度与吸力比(吸力与进气值之比)关系可以归一;通过建立进气值与构度指标之间的定量联系,构建了可统一考虑冻融循环作用影响的修正持水模型;初步证实了冻融循环条件对原状黄土持水曲线的影响,可以通过土的构度指标变化引起进气值的改变来反映。

Freeze-thaw acting is an important factor that can’t be ignored in engineering disasters such as loess slope slump and roadbed subsidence.Water retention behaviour is the key physical property for analyzing the hydraulic-mechanical properties of unsaturated loess,and it needs to be further studied that how freeze-thaw cycle affects water retention behaviours of loess.This test took intact loess after freeze-thaw cycles as research objects and studied how both the number of freeze-thaw cycles and the water content before freeze-thaw affect the soil-water retention curve(SWRC)and its characteristic parameters.The results show that the effect of freeze-thaw cycles on SWRC is fluctuating,and the degree of influence is controlled by the number of cycles and the initial water content before freeze-thaw.The relationship between saturation and ratio of suction(ratio between suction and air-entry value)can be normalized under different freeze-thaw conditions.By establishing quantitative relationship between the air-entry value and the structure index,a modified water-retention model was proposed to consider the effect of freeze-thaw cycles uniformly.The effect of freeze-thaw cycle conditions on the SWRC of intact loess is preliminarily confirmed,which can be reflected by the change of air-entry value caused by the change of soil structure index.