考虑竖井作用的填埋场气-液耦合运移规律

Flow equation for gas-leachate coupling effect considering vertical wells in landfills

为研究存在竖井的填埋场中填埋气、渗滤液的运移规律,在忽略气、液竖向流动的前提下,基于有机物生化降解、气-液本构关系和气、液连续性条件,结合抽气、回灌渗滤液等工况,建立填埋场平面轴对称气-液耦合运移理论,得到被动集气和主动集气2种工况下的简化解析解。计算结果表明:孔隙水压力和孔隙气压力均随离开竖井距离的增大而增大;孔隙水压力随时间逐渐消散,孔隙气压力先达到峰值再消散;考虑液相对孔隙气压力的耦合影响时,孔隙气压力有所提高;气相渗透系数增大会减小液相对孔隙气压力的耦合影响,液相渗透系数增大会加剧耦合影响。

In this study, the flow of gas and leachate to vertical wells in landfills was investigated. Neglecting the flow of landfill gas and leachate in the vertical direction, and based on the degradation of organic matter, gas-leachate constitutive relationship, and gas-leachate continuous conditions, the flow equation under the condition of a plane axisymmetric gas-leachate coupling effect was established with gas pumping and leachate recirculation. The analytical solution in the unsteady state of the simplified equation is presented under conditions of passive and active extraction wells. The results show that the pore water pressure and gas pressure increased with the distance from the extraction well. The pore water pressure dispersed as time went on, and the gas pressure increased to its peak value initially, and then dispersed. The gas pressure that considered the gas-leachate coupling effect was relatively higher. The coupling effect on gas pressure was reduced with the increase of gaseous permeability, and become more significant with the increase of liquid permeability.