填埋场成层衬垫污染物运移参数等效模型

Equivalent model for pollutant transport parameters of layered landfill liners

为了高效评价填埋场成层衬垫的防污性能,提出基于时间矩卷积的污染物运移参数等效分析模型.给出多层衬垫等效渗流速度和扩散系数表达式;采用土柱实验数据验证模型的合理性和可靠性;基于衬垫系统底部相对浓度、瞬时通量及累计通量等对填埋场土工膜(GM)+压实黏土衬垫(CCL)+天然衰减层(AL)及GM+钠基膨润土防水毯(GCL)+AL不同复合衬垫进行等效计算.结果表明,衬垫底部相对浓度更适合等效计算.随设计水头与AL厚度增加,GCL复合衬垫的防污性能较好.基于Cl-击穿时间100 a标准,当水头为15 m时,与采用CCL相比,采用GCL复合衬垫可以使总厚度减少0.45 m.土工膜防污能力随水头增加而增强,土工膜等效的CCL厚度随服役年限呈对数线性增大.

An equivalent analytical model for pollutant transport parameters based on time moment convolution was proposed in order to efficiently assess the performance of layered landfill liners.Expressions of equivalent seepage velocity and diffusion coefficient of multilayer soil liners were derived.The proposed equivalent model was verified by experimental data from soil column tests.The equivalent calculation of geomembrane(GM)+compacted clay liner(CCL)+natural attenuation layer(AL)and GM+geosynthetic clay liner(GCL)+AL were carried out in terms of relative concentration,instantaneous flux and accumulative flux at bottom of the liner system.Results show that the relative concentration at the bottom of the liner system is the more conservative parameter for assessment of the layered landfill liner system.GCL composite liner has better performance with the increase of design leachate head and AL thickness.Based on the standard with Cl-breakthrough time 100 years,the total thickness for the case with GCL composite liner can be 0.45 m less than that of the CCL composite liner when leachate head is 15 m.The antifouling capacity of geomembrane increases with the increase of leachate head.The equivalent CCL thickness of geomembrane increases log-linearly with the service life.