降雨入渗条件下膨胀土基坑边坡离心试验

Centrifugal Test of the Expansive Soil Foundation Slope under Rainfall Infiltration

降雨是引起膨胀土基坑边坡失稳最主要的因素。以成都某膨胀土基坑边坡为原型,建立了一个0.6 m×0.4 m×0.4 m的相似模型,施加40 g离心加速度及模拟降雨作用,测试模型的变形及含水率特征。结果表明,降雨入渗对膨胀土基坑边坡的影响包括:膨胀土强度降低导致桩后的主动土压力增大,以及导致锚固段抗力降低,膨胀土吸水产生附加膨胀力。悬臂桩支护下的直立型膨胀土基坑边坡形成的破裂面可分为两段:上段为拉张性质,近竖直;下段为剪切闭合性质,呈圆弧型。破裂面的上边界位于坡后1/2～2/3坡高处,下边界位于坡脚。

Rainfall is one of the most important factors for the instability of expansive soil foundation pit slope. An expansive soil excavation slope in Chengdu is used as a prototype to establish a similar model of 0.6 m×0.4 m×0.4 m. The model was applied with 40 g centrifugal acceleration and affected by rainfall. The deformation and moisture content characteristics of the model are measured. At the same time, a numerical model was established according to the centrifugal model. Comparing and analyzing the results of field monitoring, centrifugal tests and numerical simulations, we can see that under the effect of rainfall infiltration, the strength of expansive soil decreases, the active earth pressure behind the pile increases, and the anchorage section resistance decreases, and that the expansive force generated by expansive soil absorbs water, and the slopes are more prone to damage. The effect of rainfall infiltration is greater than the effect of excavation unloading. The sliding surface formed by the slope of an upright expansive soil foundation pit supported by cantilever piles can be divided into two sections: the upper section is tensile, and the vertical section is near vertical;the lower section is shear closed and is arc-shaped.