Study On Drainage Capacity Of Leachate Collection System In Muncipal Solid Waste Landfill

With the rapid expansion of the cities size,in order to eliminate the environment pollution caused by municipal solid waste,a number of modern sanitary landfill are builded in China.Technical Code for Municipal Solid Waste Sanitary Lanfill(CJJ17-2004) provides that the Leachate Collection and Remove System(LCRS) must be set up in landfills,but calculation method and control standard don't involve.However,if the leachate collection system is ineffective or failure,it lead to excessively high water level,increase the risk of pollution,affect the stability of the landfill,and may endanger the safe poration of landfill.So, it has value of great theoretical and significant engineering applications to analysis of different types of leachate collection system,theoretical analysis and numerical calculationFocused on the continuous-slope configuration drainage system and the saw-tooth configuration drainage system,theoretical calcution and numerical analyses were carried out, study the characteristics of the pheratic line,the main contents and conclusions are as follows:(1) Research achievements on leachate maximum saturated depth and phreatic-surface of landfill at domestic and foreign were summed up.Based on an extended form of the Dupuit assumption,govern equation of leachate maximum saturation depth was derived for the saw-tooth configuration of drainage system.According to the concept of hydraulic radius,the hydraulic radius formula of the dranage pipe is given,Through the introduction of parametes to give the relationship between the relative hydraulic radius and the relative depth,hydraulic radulic of arbitrary depth and arbitrary depth can easy to find out.(2) Govern equation for the steady-state phreatic surface in continuous-slope configuration of the drainage system are derived on the Dupuit assumption.Compaired the maximum saturation depths with McBean(1993) method's,it proved the feasibility of the method.As the drainage liner slope is large,another goven equation for the steady state phreatic surface is given.Results demonstrate the results of two assumptions are close when the slope less then ten precents,recommendations for the smaller slope,the former method can be used to calculate.Drainage efficiency of the saw-tooth configuration drainage system is better than the continuous configuration drainage system's.By parametric analysis to discussion the various parameters impact on the maximum saturation depth in continuous configuration drainage system. (3) Through the finite element software to simulate the steady-state flow in saw-tooth configuration drainage system to determine the maximum saturated depth,summed up the law by changing the parameters.Results shows drainge slope is of great influence on the maximum saturation depth,as working condition is allowed,the drainage liner slope will be large as far as possible to drope leachate level,accurate identification of drainge ditch (drainge pipe) is very important on the accurate calculation of the maximum saturated depth.