水泥固化体淋滤液对GCL防渗性能的影响

水泥固化/稳定化是危险废弃物处理的经济、高效方法,然而,水泥固化体的淋滤液中含有大量Ca²⁺,其长期渗透有可能导致填埋场底部土工合成黏土衬垫(geosyntheticclayliner,GCL)的防渗性能下降,从而引发二次污染。使用柔性壁渗透仪,测定有效应力和水泥固化体淋滤液共同作用下GCL的渗透系数,探讨了淋滤液浓度以及不同有效应力对GCL渗透系数的影响。试验结果表明:当有效应力为24kPa时,水泥固化体淋滤液的持续渗透会使GCL的渗透系数增大179～721倍,淋滤液中Ca²⁺浓度越高,GCL渗透系数增大的幅度越大。通过增加有效应力,可以降低固化体淋滤液对GCL防渗性能所造成的负面影响,当有效应力增大至438 kPa时,固化体淋滤液对GCL防渗性能所造成的负面影响全部被抵消。

Influences of stabilization/solidification product leachates on hydraulic performance of geosynthetic clay liners

Cement solidification/stabilization is an economical and efficient method to dispose hazardous waste. However, the leachates from portland cement stabilization/solidification product landfills generally contain high concentration of Ca²⁺, which may has detrimental effects on the long-term hydraulic performance of geosynthetic clay liners (GCLs), and cause a secondary pollution. Therefore, hydraulic conductivity tests are performed on the GCLs using two leachates and five effective stresses. The test results show that permeation of leachates results in an increase in the hydraulic conductivity of 179 to 721 times under the effective stress of 24 kPa, and the higher the concentration of Ca²⁺ in the leachates, the higher the hydraulic conductivities of the GCLs. The negative effects of the leachates can be offset by the effective stress applied on the GCLs. For example, when the effective stress increases to 438 kPa, the hydraulic conductivities to the leachates are comparable to those obtained for the controlled specimens (permeated with tap water), and the detrimental effects resulting from the permeation of the leachates are balanced completely by the effective stress.