降雨/蒸发对膨胀土边坡稳定性影响研究

Influences of precipitation and evaporation on the stability of expansive soil slopes

为深入研究降雨/蒸发作用对膨胀土边坡稳定性的影响,本文将改进的二维渗流模型与极限平衡分析法相结合,计算分析降雨、蒸发两种不同类型的气候作用下试验场地膨胀土边坡体内的渗流场变化及边坡的稳定性;结合试验边坡的现场监测资料,论述了膨胀土边坡的失稳机理。本文的研究表明:持续降雨引发土体吸力降低、强度衰减、有效应力降低并在坡脚处首先达到极限平衡状态;蒸发作用使浅层土体含水量降低,吸力增加,但同时也出现的收缩作用将产生裂隙而折减土体强度且增强渗透性,但土体内吸力的大幅提高则起主导作用。本文的研究成果将有助于分析评价膨胀土边坡在遭受干湿循环作用下的长期稳定性。

In order to study the influences of precipitation and evaporation on the stability of expansive soil slopes,the improved two-dimensional Richards seepage model and the limit equilibrium approach are combined to analyze the variation of the seepage field and the stability of the slopes considering the precipitation and evaporation regarded as two major factors causing slope failure. The failure mechanism of the slopes is analyzed based on the field monitoring data. The study shows that the heavy rainfall causes the decreases of soil suction,the effective stress and the strength of expansive soils,and the toe of slope would be in limit equilibrium state. On the other side,the water content of soils decreases and the suction increases enormously under the evaporation,and the fissures would occur owing to the differential shrinkage of expansive soils,which could not only decrease the strength,but also increase the permeability. The study will be helpful to analyze the long-term stability of expansive soil slopes under the wet-dry effect.