膨胀土边坡物理模型试验研究

进行了一系列压实膨胀土的大型静力模型试验,对边坡土体吸湿后的含水率、膨胀变形等进行了实时监测。试验成果显示,膨胀土边坡浅层土体吸湿后其含水率场分布不均匀,干湿分界面处土体易由于不均匀膨胀变形而导致局部剪切错动,并随水分在坡体内的迁移,局部滑动面逐渐向边坡纵深扩展,在不同深度、不同部位形成多重剪切滑动面,最终导致边坡整体塌滑。针对静力模型试验进行了考虑膨胀性的非线性有限元计算,比较了边坡自重条件下和吸湿后应力场的变化,可知吸湿引起顺坡向正应力在干湿分界面处变化剧烈,剪应力明显增大,强度折减法得到的模型试验边坡安全系数仅0.92。研究成果表明：影响膨胀土边坡浅层稳定性的最根本原因并非膨胀土的超固结性或裂隙性,而是土的胀缩特性。

Physical model tests on expansive soil slopes

A series of large-scale static model tests on a compacted expansive soil slope under artificial rainfall are conducted for real-time monitoring of water content and swelling deformation. The monitoring results show that the distribution of water content in the slope is nonuniform in space and time, which results in the nonuniform distribution of swelling deformation at the drying-wetting interface. According to the survey of failure surface by excavation after landslide, it is observed that local shear ruptures firstly take place at the drying-wetting interface within the shallow layer of slope, and then extend downwards gradually with water infiltration, and multiple shear sliding surfaces are produced at different depths and areas, which connect further with each other and finally lead to an overall landslide. The traditional limit equilibrium method can not correctly simulate the progressive landslide of expansive soil slopes. The finite element method with expansive model is adopted, and the safety factor of the model test slope is calculated to be 0.92 using the strength reduction technique. Both the physical model tests and the finite element analysis prove that the essential influence factor of expansive soil slope stability is the swelling deformation instead of the over-consolidation effect and fissure presence.