非饱和膨胀土边坡中土水相互作用机理

Study on soil-water interaction in unsaturated expansive soil slopes

为了探讨非饱和膨胀土中强烈土水相互作用对边坡稳定的影响,进行了大型现场降雨入渗模拟试验和综合的室内试验研究.研究了包括土水特征曲线的测试、胀缩试验和吸湿软化试验的室内试验.试验成果分析表明,在干湿季节循环过程中,非饱和膨胀土中水分、吸力、变形、应力和抗剪强度之间发生强烈耦合作用.膨胀土的丰富裂隙在土水相互作用中起关键作用,它直接破坏了土体的完整性,并显著增加了表层土的入渗速率.降雨入渗使得浅层的非饱和膨胀土体发生吸水膨胀而软化,还造成浅层土体中水平应力显著增加,这可能导致土体发生局部被动破坏.季节性干湿循环使得边坡浅层土体逐渐发生向坡下蠕变,以致边坡发生渐进累积破坏.

In order to study the influence of the intensive soil-water interaction in an unsaturated expansive soil on the slope stability, a full-scale rainfall infiltration test and a comprehensive laboratory study were carried out. Laboratory studies including measurement of soil-water characteristic curve, swelling and shrinkage tests and wetting-induced softening tests were performed. The test results indicated an intensively coupled interaction among the changes in water content, suction, stress, deformation and shear strength occurs to the unsaturated expansive soil during the seasonal wetting-drying cycles. The abundant cracks in the expansive soil play an important role in the soil-water interaction. The cracks disintegrate the soil mass, and increase the infiltration rate of the surficial soil layer. Rainfall infiltration not only results in a wetting-induced swelling and softening of the shallow unsaturated soil layers, but also leads to significant increase in the horizontal stress. The increase in horizontal stress may lead to local passive failure. The seasonal wetting-drying cycles result in a down-slope creeping of the shallow soil layer, leading to progres sive slope failure.