Stability Analysis And Control Measures Of Municipal Solid Waste Slope

With the improvement in the urbanization level, the generation of municipal solid waste (MSW) increases rapidly in China. In order to enlarge the capacity of landfills, the filling height increases more and more, and extension projects of the existing landfills are common now. Due to lack of knowledge of the strength of MSW, landfill failure took place worldwide, leading to casualty and property losses and enormous environmental disaster. For evaluating existing landfills correctly and designing modern sanitary landfills rationally, field monitor and laboratory tests were performed to investigate the strength of MSW, the stability analysis method, value of key parameters and evaluation standard of MSW landfill were analyzed systematically, and the effect of sludge pit in landfill on landfill stability was specially discussed.Field monitor and laboratory tests were carried out in Suzhou Qi-zi-shan landfill and Shenzhen Xia-ping solid waste landfill. The results show that with increasing the filling depth, compactness, strength and friction angle of MSW increase, while cohesion decreases. There are often mutil-layered leachate levels for many intermediate overburden layers in waste body.Sliding patterns and methods of stability analysis were summarized. By comparison of calculation results obtained by waste-homogenization and waste-layering, the former shows some slightly conservative, and both come to closer. Main leachate level can be considered as replacing leachate level when there're mutil-layer leachate levels in landfill. The composite liner system is simulated as 1.0m soft soil layer in analysis of MSW landfill stability, which is reasonable and feasible.The stability safety factor of MSW landfill gradually decreases with decreasing MSW gravity, increasing slope gradient. Leachate level has a great effect on MSW stability. When leachate level over 0.5h/H, the leachate level increased 10% each, stability safety factor will be decreased about 25%, and the reducing rate become larger. For landfill internal failure, the proposed leachate water level is 0.7h/H. The interface strength can adopt peak strength at or close to horizontal bottom and residual strength at slope when displacement-softening effect takes place at the weak interface of the composite liner at the bottom.It is prohibited filling waste on and near the sludge pits, and should preserve safety region more than 50m. The sludge pit severely weakens the stability of landfill slope, so that reinforcement measurements must be taken to meet the filling demand, then follow-up filling can be arranged.Unstable landfill body can be handled through an integrated control measures, including: layout downslope drains, shaft drainage pump, the back-pressure layer and cover layer. Leachate level control measures are the most effective long-term stability control measures, including:the horizontal drains, deep shaft drainage pump and drainage pipe cleaning-up technology etal.