黄土淋滤液作用下土工合成黏土衬垫的渗透特性研究

摘要

A series of laboratory hydraulic conductivity (K) tests were conducted to evaluate the potential of two Geosynthetic clay liners (GCLs) used as a final cover material for coal gangue impoundment.During the experiment,loess leachate was used as permeant liquid.Under a relatively low effective stress of 15 kPa,the K values of both GCLs were approximately 2.80×10-9 m/s,which were higher than 1.00×10-9 m/s and couldn't satisfy the technical requirement for the cover of coal gangue impoundment.However,when the effective stress increased to 90 kPa,the K of the GCL was approximately 3.52×10-10 m/s,which met the above requirement.The results indicated that there was no distinct difference between the hydraulic performances of the two different GCLs.The results of this study also indicated that increases in effective stress can minimize the detrimental effect of loess leachate permeation on the hydraulic performance of GCLs;however,in order to make the GCL satisfy the requirement,the thickness of the surface loess layer must be higher than 5.0 m,which is not easy to achieve in the field.Therefore,it is necessary to study GCLs with certain ability of resistance to chemical erosion in future.%通过开展室内渗透试验,评价两种不同类型土工合成黏土衬垫(Geosynthetic Clay Liner,GCL)用作煤矸石处置场覆盖层的可行性.试验中,使用黄土淋滤液对天然钠基膨润土GCL和人工钠化膨润土GCL进行渗透.当有效应力为15 kPa时,两种GCL的渗透系数均在2.80×10-9 m/s左右,此值高于1.00×10-9 m/s,无法满足煤矸石处置场覆盖层的防渗要求;而当有效应力增大至90 kPa时,GCL的渗透系数则降低至3.52×10-10 m/s,满足防渗要求.试验结果显示:黄土淋滤液渗透作用下两种GCL的渗透特性没有显著差别.增大有效应力,可降低黄土淋滤液对GCL渗透特性的影响,但为了使GCL满足煤矸石处置场覆盖层的防渗要求,其上部黄土植被层的覆盖厚度必须达到5.0m以上,这在现场不易实现,故今后有必要对具有一定抗化学侵蚀能力的GCL展开研究.