降雨蒸发条件下膨胀土边坡的变形特征研究

在典型膨胀土广泛分布的广西南宁地区建立缓坡、陡坡与坡面种草3种类型膨胀土边坡的原位监测系统,采用6参数小型气象站、测斜管和沉降板,跟踪测试边坡变形随气候变化的演化规律,揭示在降雨蒸发下膨胀土边坡的变形特征。认为降雨是导致膨胀土边坡变形最直接的气候因素,而蒸发效应是边坡变形破坏的重要前提之一;蒸发效应所产生的土体裂隙,使得吸湿条件下原位双环渗透试验获得的膨胀土水力特性具有与传统的非饱和土力学中的定义有相反的趋势,这也是膨胀土边坡在降雨入渗时发生变形乃至破坏的内在机制之一;通过对现场试验数据的拟合,建立了符合膨胀土边坡变形的经验性预测模型,其中边坡变形与土表净入渗量呈二次函数关系。

Deformation characteristics of expansive soil slopes under precipitation and evaporation

A field monitoring system is set up to measure three types of expansive soil slopes,i.e.gentle slope,steep slope,and slope planted with grasses,in Nanning,Guangxi province,where expansive soils are extensive.Variations of the deformations of these three types of slopes with the climate are measured by a six-parameter mini-meteorological station,inclinometers and settlement plates,to reveal the evolutions of deformation characteristics,in which precipitation is regarded as the most direct factor and evaporation effect is an important precondition.Cracks due to evaporation make the hydraulic properties of the expansive soils obtained through in-situ double ring infiltrometer test have a wetting trend opposite to the traditional definition in unsaturated soil mechanics,which is also an important mechanism.Based on fitting the in-situ measured data,an empirical prediction model for the deformation of expansive soil slopes is established,in which the relationship between slope deformation and net infiltration of the soil surface is quadratic.