压实膨润土的土水特性试验研究

回填材料是高放废物地质处置库多重屏障系统的重要组成部分,以蒙脱石为主要成分的膨润土是较理想的回填材料,研究膨润土的非饱和渗透特性,对于回填材料选材和处置库安全性评价具有重要意义。文章通过室内试验开展柯尔碱膨润土的土水特性研究,用压力膜仪实测不同干密度柯尔碱膨润土的土水特征曲线,根据柔性壁渗透仪测得的饱和导水率数据,采用Van Genuchten(1980)预测模型分别计算得到每种干密度膨润土在不同含水量及基质吸力条件下的非饱和导水率,建立了非饱和导水率与含水量、基质吸力的相关关系,对比分析干密度对曲线的影响。结果表明,干密度对柯尔碱膨润土的土水特征曲线有着明显的影响,在初始含水量相同的情况下,干密度较大的膨润土脱水速率比干密度较小的膨润土脱水速率慢,表现出较高的持水性能。柯尔碱膨润土的非饱和导水率随含水量减小和基质吸力增大皆呈非线性降低,干密度越小,非饱和导水率越大。

Experimental Study on Soil-Water Characteristics in Compacted Bentonite

Buffer backfill material is an important part of multi-barrier system in HLW geological repository.Bentonite is an ideal buffer backfill material,which is mainly composed of montmorillonite.The research of bentonite's non-saturated hydraulic properties is important to backfill material selection and repository safety evaluation.Soil-water characteristics of cole alkali bentonite by laboratory tests were studied.Pressure plate extractors were used to measure soil-water characteristics curve of cole alkali bentonite of different densities.The saturated hydraulic conductivity of bentonite was tested by flexiblewall permeameter,and then unsaturated hydraulic conductivity in different water contents and matrix suction was calculated through Van Genuchten(1980)prediction model.Based on measurement and calculation,the correlation between unsaturated hydraulic conductivity and water content(matrix suction) was established,and impact of dry density on the curve was comparative analyzed.Results showed that the unsaturated hydraulic conductivity of cole alkali bentonite decreased in nonlinear trend with water content decreased and matrix suction increased.