泄滩滑坡碎块石土饱和与非饱和水力学参数的现场试验研究

Field tests of saturated and unsaturated hydraulic parameters of gravelly soil in Xietan landslide

碎块石土由于块石含量较高,块石粒径较大,其水力学参数的确定具有一定困难。首先,采用双套环法对三峡库区泄滩滑坡的滑体碎块石土饱和渗透系数进行了原位试验,并根据土层孔隙率、颗粒级配等因素采用相关经验公式对试验结果进行了分析。其次,结合使用张力计和体积含水率仪对其土水特征曲线进行了现场模拟试验,并采用Fredlund模型对试验结果进行了拟合分析。最后,根据土水特征曲线和饱和渗透系数,采用经验公式估算了其非饱和渗透系数。试验及分析表明,该滑坡的碎块石土层的饱和渗透系数为(1.78～3.2)×10-2 cm/s,为强渗透性;材料的细颗粒含量越少,有效粒径及控制粒径越大,不均匀系数越小,相应的渗透系数越大。相关研究成果可以为泄滩滑坡非饱和非稳定渗透计算提供参数依据,并对同类型土体非饱和水力学参数的确定具有一定的借鉴意义。

The hydraulic parameters of gravelly soil arc difficult to determine due to its high gravel content and large grain size. The field permeability tests of gravelly soils layer of the slidebody of Xietan landslide have been carried out by double ring; and the test results are analyzed by empirical formulas, considering the soil porosity, grain-size distribution etc. Then, the soil-water characteristic curve （SWCC） is tested by the method of tensiometer-moisture content and fitted by Fredlund model. And finally, the unsaturated permeability coefficient of gravelly soil is calculated by empirical formulas based on its SWCC and saturated permeability coefficient. The test data demonstrate that, the saturated permeability coefficient of gravelly soil layer is quite good with permeability coefficient varied between 1.78×10^-2cm/s to 3.2 ×10^-2cm/s; smaller fine grain content, bigger effective grain size and controlling grain size will lead to larger permeability coefficient. Through these works, the unsaturated hydraulic parameters are determined for the unsaturated seepage analysis of Xietan landslide; and the technique can be used as reference for similar soils.