低含水率砂土边坡离心模型试验与数值模拟

Centrifugal Model Test and Numerical Simulation of Sandy Slope with Low Moisture

针对低含水率砂土边坡失稳过程中的应力应变场演变过程和水分迁移规律,采用离心模型试验与数值模拟相结合的方法进行研究。此外,分析了低含水率砂土似黏聚力的产生原因,提出了其计算方法,并阐明了低含水量非饱和砂土抗剪强度出现峰值效应的机理。研究表明:各模型均呈浅表层崩塌,对应的失稳破坏离心加速度值分别为24.6g,44.3g和40.0g。随着离心加速度增加,应力梯度增大,剪应变从靠近坡脚处向坡顶逐步发展,最终在坡体内形成了塑性贯通的滑裂面,边坡发生滑动失稳。离心试验后水分明显向坡体深处转移,浅部含水量在残余含水量附近波动。当土水特征曲线拟合参数与基质吸力二者满足一定关系式时,低含水率砂土的似黏聚力将出现极大值。

By adopting centrifugal model test and numerical simulation, the development and the regularity of moisture migration of stress-strain field during failure of sandy slope with low water content is studied. Additionally, the cause of ＂apparent cohesion＂ of low water content sand is analyzed, its calculation method is suggested, and the mechanism of peak effect of shear strength in unsaturated sand with low water content is clarified. The research shows that （1） all models present sudden shallow collapse, and the corresponding unstable failure centrifugal acceleration values are 24.6g, 44.3g and 40. 0g respectively; （2） with the increase of centrifugal acceleration, stress gradient became higher, shear strain developed from slope foot towards top and finally formed slip surface with run-through plastic zone in the slope; （3） after centrifugal test, water transferred downward distinctly, and shallow sand layer remained at a ＂residual moisture＂ ; （4） when the fitting parameters of soil-water characteristic curve and the matric suction satisfies certain equations, the ＂apparent cohesion＂ of low water content sand would reach a maximum value.