不同降雨模式下山谷型垃圾填埋场水分运移及其稳定性研究

Investigations of water transport in valley-type MSW landfills and their stabilities subjected to various rainfall patterns

近10年的运营经验表明,国内南方地区第1批建造的山谷型垃圾填埋场中的渗滤液水位一般较高。同时,现有研究表明,降雨入渗引起渗滤液水位过高是垃圾填埋场失稳的主要诱因之一。因此,研究强降雨条件下山谷型垃圾填埋场的水分运移规律及其稳定性,具有重要的现实意义。基于七子山填埋场浅层、中层和深层垃圾土的土-水特征曲线和Brooks-Corey公式,利用非线性拟合技术得到垃圾土的渗透性函数;运用饱和-非饱和渗流理论,对递减型、中心型、增强型和平均型4种降雨模式下七子山填埋场的水分运移进行了数值计算;利用极限平衡理论,对不同降雨模式下七子山填埋场的稳定性进行了分析。结果表明,降雨模式对山谷型垃圾填埋场内的水分运移规律和填埋场的稳定性有显著的影响,递减型降雨模式下填埋场内孔隙水压的变化最大,同时填埋场稳定系数也下降最为明显,为最不利降雨模式;经历7 d 746 mm的极端强降雨后,七子山填埋场具有极大的失稳隐患。

It is shown that the water tables of leachate in many early valley-type MSW landfills in Chinese Southern Region are very high by the operating experiments in last ten years.It is shown that the high water table of leachate by rainwater infiltration is a main factor induced MSW landfill landslide by many literatures.So,it is very important to investigate the water transport responses and the stability of valley-type MSW landfills under heavy rainfall.Firstly,based on the soil-water characteristic curve of shallow,middle and deep layer MSW in Qizhishan landfill and Brooks-Corey equations,the permeability function of MSW landfills is given by nonlinear curve fitting.Secondly,numerical analyses are conducted to investigate water transport in Qizhishan valley-type MSW landfill subjected to rainfalls with four different patterns,i.e.delayed,central,advanced and uniform rainstorms.At last,the stability of Qizhishan landfill has been studied by limit equilibrium method.The computed results show that rainfall pattern has a significant influence on water transport in valley-type landfill and its stability,and the delayed rainfall is found to be the most critical one because it results in the highest pore-water pressure in the landfill and the smallest safety factor of landfill.Numerical results show that the safety factor of landfill reaches 1.016 after 746 mm rainfall with duration of 7 days,and the possibility of landside in Qizhishan landfill is very great.