干湿循环与垃圾渗滤液耦合作用下GCL防渗性能

Hydraulic performance of GCL under wet-dry cycling concurrent with municipal solid waste leachate permeation

开展膨胀指数和渗透系数测定试验,研究干湿循环与垃圾渗滤液渗透耦合作用下膨润土的膨胀性能和土工合成黏土衬垫(GCL)防渗性能变化规律.结果表明,干湿循环与垃圾渗滤液渗透耦合作用对膨润土的膨胀性能和GCL的防渗性能具有显著负面影响:在7次干湿循环后,垃圾渗滤液饱和的膨润土的膨胀指数从20mL/2g降低至7.5mL/2g,GCL的渗透系数从1.65×10-11m/s增加到1.89×10-7m/s.膨胀指数下降和渗透系数升高的根本原因是膨润土渗透膨胀性能的丧失.单纯的垃圾渗滤液渗透不会改变GCL的渗透系数.将有效应力从20kPa升高至150kPa,可以促使GCL的渗透系数降低4个数量级,满足填埋场防渗要求(<5.0×10-11m/s).

Laboratory free swell and hydraulic conductivity tests were conducted to assess the effect of wet-dry cycling concurrent with landfill leachate permeation on the swell index of bentonite and hydraulic performance of a geosynthetic clay liner(GCL).Wet-dry cycling concurrent with leachate permeation had a significantly detrimental effect on the swell index of bentonite and hydraulic performance of GCL.The swell index of bentonite decreased from 20mL/2g to 7.5mL/2g and the hydraulic conductivity of GCL increased from 1.65×10-11m/s to 1.89×10-7m/s.The decrease in the swell index of bentonite and the increase in hydraulic conductivity of GCL should be attributed to the loss of osmotic swell of bentonite.The GCL continuously permeated with municipal solid waste leachate maintained a low k during the entire study duration.Increasing the effective stress from 20 to 150kPa caused the hydraulic conductivity of GCL to decrease by almost 4orders of magnitude and lower than the maximum value(5.0×10-11m/s)allowed for GCL used in municipal solid waste landfill.