南宁灰白膨胀土三向膨胀率试验研究

Three-Dimensional Expansion Rate Test of Grey-White Expansive Soils in Nanning

采用自行研制的三向膨胀仪,以南宁灰白色膨胀土为研究对象,开展三向膨胀率室内试验。结果表明:膨胀土浸水后,膨胀速率可分为快速膨胀、缓慢膨胀、趋于稳定三个阶段,6 h基本完成膨胀,竖向膨胀率大于横向膨胀率,两个横向膨胀率大致相等;横向膨胀率与竖向膨胀率的比值R0随着干密度的变化而不同,变化范围为0.61~0.82。在相同初始含水率条件下,R0随干密度的增大而增大,说明膨胀土干密度越大,各向异性越弱;相同含水率条件下,膨胀率随干密度的增大而增大,含水率越大,竖向膨胀率随干密度的变化速率越小;相同干密度条件下,膨胀率随含水率的增大而减小,干密度越大,膨胀率随含水率的变化速率越大。

It is very important to study the three-dimensional expansion characteristics of expansive soils for the stability analysis of slopes with expansive soils.In this experiment,an inhouse developed three-dimensional expansion testing device was used to test the three-dimensional expansion rate in the laboratory conditions of the grey-white expansive soil samples in Nanning.The results show that:after soaking,the expansion rate of expansive soil samples can be divided into three stages:the rapid expansion,the slow expansion and stabilization phases.The 80%~90%of the entire expansion process can be completed within three hours,and the overall expansion can be generally completed in six hours.The vertical expansion rate of the sample is larger than the lateral expansion rate,and the lateral expansion rates in two different directions are roughly equivalent.The ratio R0 of expansion rate to vertical expansion rate varies with the initial dry density,ranging from 0.61 to 0.82.Under the same initial moisture content condition,R0 increases with the increase of dry density,which indicates that the greater the dry density of expansive soil,the weaker the anisotropy of the sample.Under the same initial moisture content condition,the expansion rate increases with the increase of dry density of soil sample,and the higher the moisture content,the smaller the change rate of vertical expansion rate with the initial dry density;Under the same initial dry density,the expansion rate decreases with the increase of initial water content,and the higher the dry density,the higher the vertical expansion rate with the initial water content.