不同有效应力下矿山渗滤液对土工合成黏土衬垫渗透特性影响的试验研究

Hydraulic conductivity of mine leachate through geosynthetic clay liners under different effective stresses

以模拟矿山渗滤液作为渗透溶液,使用柔性壁渗透仪,在不同有效应力条件下测定土工合成黏土衬垫(geosynthetic clay liner,GCL)的渗透系数。试验结果表明:矿山渗滤液作用下GCL渗透系数升高的幅度与其所受有效应力的大小紧密相关;当有效应力为24 kPa时,矿山渗滤液的渗透使GCL的渗透系数升高至1.52810-′m/s,比控制样(自来水渗透)的渗透系数高340倍,不能满足《一般工业固体废物贮存、处置场污染控制规范》对防渗层渗透系数的要求(k≤1.0910-′m/s)。而当有效应力为93、162、231和438 kPa时,矿山渗滤液的持续作用使GCL的渗透系数只分别升高了26、21、14和10倍,且全部满足规范要求。研究结果表明,在对矿山废弃物处置场中GCL的防渗性能进行评估时,必须考虑GCL试样在场地中的受力状态。

The hydraulic conductivity of mine leachate through the geosynthetic clay liners （GCLs） was tested using the flexible wall permeameter under different effective stresses. The result of test shows that the increase in the hydraulic conductivity of the GCL permeated with simulated mine leachate was strongly related to the effective stress applied on the GCLs. Under a relatively low effective stress of 24 kPa, the hydraulic conductivity of GCL permeated with simulated mine leachate was up to 1.52×10^-8 m/s, about 340 times greater than that of GCL permeated with tap water. The GCL was not able to satisfy the requirement specified in the standard for pollution control on the storage and disposal site for general industrial solid wastes. However, the hydraulic conductivity decreased to 26, 21, 14 and 10 times of the number for tap water when the effective stress increased to 93, 162, 231, and 438 kPa, respectively. All the hydraulic conductivity values of GCL obtained during these test stages were lower than the specification in standard. The results of this study indicated that the stress state for GCL expected in the field should be considered when evaluate the hydraulic performance of GCLs that considered as a liner for a tailing impoundment.