中文摘要：

为了评价填埋场覆盖层对挥发性气体的防渗性能，建立了挥发性气体在复合覆盖层中的扩散运移模型并采用分离变量法获得了模型解析解。解析解的计算结果与数值解结果吻合得较好。分析结果表明，对于土工膜／土工复合膨润土垫（GM／GCL）与土工膜／压实黏土（GM／CCL）组成的覆盖层，覆盖层顶部气体扩散达到稳态的时间比较接近，约为1．6a；对于压实黏土（CCL）系统达到稳定状态的时间为0．5a；稳态时通量依次为6．0×10^5，1．0×10^5和7．4×10^5mg／ha／a。在这3个覆盖层系统中，GM／CCL对气体扩散的控制性能最差。对于GM／GCL，GCL含水饱和度从0．85增加到1时，覆盖层项部通量减小了82．5％。饱和时GM／GCL系统顶部气体达到稳态的时间是非饱和情况下的约100倍。对于GM／CCL，CCL含水饱和度从0．1增加到0．85时，覆盖层项部通量减小了近1个数量级。含水饱和度的变化可导致覆盖层顶部挥发性气体稳态时通量发生数量级的变化。

英文摘要：

In order to assess the effectiveness of landfill cover systems in prohibiting the emission of volatile gases, an analytical solution is developed using the method of separation of variables on the basis of the proposed gas diffusion model. The present analytical solution is found to be in good agreement with the numerical results. For the cover systems of geomembrane/geotechnical bentonite （GM/GCL） and geomembrane/compacted clay （GM/CCL）, the time for the gas flux at the top of cover systems to reach the steady state is approximately 1.6 years; and for the compacted clay （CCL）, the time is only 6 months. The corresponding gas fluxes at the top of the cover systems of GM/GCL, GM/CCL and CCL are 6.0×10^5, 1.0×10^6 and 7.4× 10^5 mg/ha/a, respectively. The composite cover system with a CCL has the largest diffusion gas flux among the three cover systems. For GM/GCL, when the degree of water saturation increases from 0.85 to 1, the gas flux at the top of the cover system decreases by 82.5%, and the time for the gas flux at the top of the system to reach the steady state for saturated cases is 100 times longer than the time for the test of unsaturated cases. For GM/CCL, the flux through the top of GM/CCL decreases by about an order of magnitude when the water saturation degree of CCL increases from 0.1 to 0.85. The variation of degree of water saturation may result in a change in the volatile gas flux at top of the cover systems by about an order of magnitude.