Study On Stability Of Landfill Due To Rainfall Infiltration

More and More landslip hazards of Municipal Solid Waste (MWS) have been happened by rainfall infiltration recently. The stability of landfill is followed with interest on a global scale. The heavy rain with certain duration acting on the landfill can cause economic lose and environmental pollution. In China, every year a vast amount of MWS are piled in the landfills, the stability of the landfill becomes a very important question for its design and construction. This paper, firstly, analyzed the stability of Yangshuiwu Landfill in north China area with complicated seepage, and then calculated extensively the stability of the landfill due to rainfall infiltration with different theories. The slope stability mechanism and failure mode are deeply dealt with in the paper.1. A indoor test and a in-site test are made to analyze the compositions and properties of MWS from LangFang Yangshuiwu Landfill and compared with other landfills to make a summary of compositions and properties of the landfills in north and south China. The date of MWS in May, September, November and March are collected respectively and then analysed the average value of its organic matter content. The result is closed to the MWS's which in Beijing Landfill, but it is different from the MWS's of landfills which in south China ares. The natural density and the water content of MWS in Yangshuiwu Landfiull is lower than its in Beijing landfill. The shear strength index is gotten by in-site static penetration test. The results are that the landfill is radical changing and the natural density, the water content, angle of internal friction and cohesion are all normal distribution.2. A simply TMC-slope FEM program was developed on the basis of Bishop slope stability theories analyzing mode. Then ACADS EXAM is used to check the correctness of TMC-slope program. The result is get by calculating the safety coefficient of landfill slope under three situations which are no seepage force, seepage force and rainfall infiltration 2.0m depth in the landfill. That is, the heavy rain with certain duration will exert a tremendous influence to the stability of MWS landfill. At same time, the safety coefficients are calculated considering on the heightand the grade of landfill. Analysis the stability of the liner of landfill system, and weakest place is found.3. Another elasticplasticity FEM program was developed on the basis of a saturated -unsaturated seepage stability mode. The transient seepage fields due to rainfall infiltration were calculated for north China area landfill and grade coefficient, seepage coefficient and height of landfill in the slope were analyzed under 100-year rainfall period is the doorsill value of the stability of MWS landfill.4. The reliability and risk analysis of the stability of MWS landfill is presented based on the view of mean rainfall and the corresponding program. Because the landfill is set up gradually and at same time the MWS were decomposited continuously. The stability of landfill is affected by the variability of c,Φvalue and grade of slope. But, the influence of MWS's natural density and height of landfill are lower than c,Φvalue. The risk analysis of engineering cost of the landfill slope can provide scientific basis for collecting a good plan of slope design and a reference plan for an investment risk analysis.