垃圾填埋场中淋滤液回灌液压变化规律

为研究垃圾填埋场中因进行淋滤液回灌而对孔隙水压力运移产生的影响,在忽略淋滤液在竖直方向上运移的前提下,在考虑填埋场淋滤液回灌的实际工况、液相本构方程、水量平衡条件和有机物生化降解的基础上,建立孔隙水压力理论方程。补充不同的边界条件,得到群井回灌和单井回灌2种情况下模型的解析解。计算及分析结果表明:(a)在进行单井回灌时,回灌进行到30 d后孔隙水压力基本稳定;孔隙水压力随离开回灌井距离的增加而迅速减小,在离回灌井15 m范围内回灌效果较好,20 m以外的区域回灌效果较差。(b)在进行群井回灌时,回灌前期孔隙水压力迅速增加,填埋单元中各处孔隙水压力最终均达到回灌水头压力;与单井相比,群井的回灌效果较好。(c)淋滤液回灌在垃圾体中会产生较高的孔隙水压力,因此在实际工程中确定回灌的时间和距离时应考虑孔隙水压力。

Change rule of hydraulic pressure during leachate recirculation in landfill

In order to study the effect of leachate recirculation on the pore-water pressure migration in a landfill, a theoretical equation of the pore-water pressure was built under the premise of ignoring the leachate migration in the vertical direction and with consideration of the actual working conditions of leachate recirculation in the landfill, the liquid phase constitutive equation, the water balance condition, and biochemical degradation of organic compounds. The equation was solved under different boundary conditions, and analytical solutions were obtained under two conditions of group-well recirculation and single-well recirculation. The results showed the following: (a)In single-well recirculation, the pore-water pressure was stable after 30 days of recirculation, the pore-water pressure quickly decreased with the distance from the well, and the recirculation effect was greater within 15 m of the well and lesser beyond 20 m of the well. (b)In group-well recirculation, the pore-water pressure increased rapidly at the beginning of recirculation, then, the pore-water pressure in the landfill cells finally reached the recirculation head pressure, and the group-well recirculation had a stronger effect than the single-well recirculation. (c)High pore-water pressure is generated during leachate recirculation in the garbage, so, in practical engineering, the pore-water pressure should be considered when determining the recirculation time and distance.