非等温分布条件下压实黏土衬垫中固结与污染物运移耦合模型研究

Coupling model for consolidation and contaminant transport in compacted clay liners under non-isothermal condition

考虑到污染场地内部产热会使得压实黏土衬垫处于非等温分布状态,建立了非等温分布条件下压实黏土衬垫中固结与污染物运移的耦合模型,并采用有限差分法对该耦合模型进行了求解。将所建耦合模型的计算结果分别与热扩散试验结果和已有理论模型的计算结果展开对比分析,对耦合模型的正确性进行了验证。基于所建耦合模型,通过某一算例分析了温度梯度M、加荷速率Q和Freundlich吸附系数K对污染物运移过程的影响。结果表明:污染物浓度和底部通量会随M绝对值的增大而增大,且一定温度梯度下的底部通量可达不考虑温度梯度时底部通量的2倍以上;Q的增大一方面会减慢污染物运移速率,另一方面会使得运移过程达到稳态时的污染物浓度增大;K的增大会减慢污染物运移过程,与不考虑吸附作用相比,考虑吸附作用可使得运移过程达到稳态时所需时间延长3倍及以上。

Considering that the heat production inside the contaminated site will make the compacted clay liner(CCL) be in a non-isothermal distribution state, a consolidation-contaminant transport coupling model for the CCL subjected to non-isothermal condition is established, and the finite difference method is used to solve the coupling model. The correctness of the established coupling model is verified by comparing the calculated results of the coupling model with the results of the thermal diffusion tests and those of the existing theoretical models, respectively. Based on the established coupling model, the effects of temperature gradient, loading rate and Freundlich adsorption coefficient on the transport process of contaminant are analyzed through an example. The results show that the concentration and bottom flux of contaminants increase with the increase of the absolute value of temperature gradient. Under a certain temperature gradient, the bottom flux of contaminant can be more than twice the bottom flux without considering the temperature gradient. On the one hand, the increase of loading rate will slow down the transport rate of contaminant. On the other hand, it will increase the concentration of contaminant when the transport process reaches a steady state. The increase of Freundlich adsorption coefficient will slow down the transport process of contaminant. The time required for the transport process to reach the steady state can be prolonged by three times or more when the adsorption effect is considered.