饱和高庙子膨润土的渗透特性

Permeability of Saturated Gaomiaozi Bentonite

在核废料深层地质处置工程中,膨润土的渗透特性是需要考虑的重要因素之一。对浸水饱和的高庙子钙基膨润土压实试样进行压缩试验,利用时间平方根法测定压缩试验中每级荷载下的固结系数,然后用太沙基一维固结理论计算土的饱和渗透系数。试验研究表明:在弹塑性阶段,计算所得饱和渗透系数随竖向应力的增大而减小,在双对数坐标下,计算渗透系数与竖向应力呈线性关系;孔隙比对渗透性起着主导作用,在半对数坐标下,计算渗透系数随孔隙比的减小而线性减小,由该线性关系得到的某一孔隙比下的计算渗透系数与公开发表的相同孔隙比的高庙子钙基膨润土的渗透系数接近。研究结果及相关文献证明应用固结理论方法间接推算膨润土饱和渗透系数的方法是可行的,该方法适用于低渗透性黏土的饱和渗透系数的量测。

Permeability of saturated bentonite is one of the essential factors for designing deep geological repository of nuclear waste. A series of one-dimensional compression tests by using oedometer are conducted on saturated compacted Gaomiaozi（ GMZ） Ca-bentonite due to wetting. The permeability coefficient is calculated by Terzaghi＇s one-dimensional consolidation theory after the consolidation coefficient is obtained by the square root of time method.The result shows that the calculated permeability coefficient decreases with increasing vertical stress in elastoplastic stage,and they show the linear relationship in double-logarithmic scale. Moreover,the void ratio is a key parameter of permeability,and the calculated permeability coefficient decreases linearly with decreasing void ratio in semi-logarithmic scale. The calculated permeability coefficient obtained through the e- log k linear relationship is close to that of GMZ Ca-bentonite with the same void ratio published in literature. The test results and related literature prove that the indirect method derived from consolidation theory is feasible to calculate the permeability coefficient of saturated bentonite. Moreover,the indirect method is suitable for saturated permeability coefficient measurement of low permeability clay.