Laboratory Research On Saturated Hydraulic Conductivity Of Municipal Solid Waste Under Different Degradation Age

Hydraulic conductivity is the a permeability indicator of the municipal solid waste (MSW). It is related to collecting leachate of the landfill, the design of drainage system and leachate storage system, leachate recharge, landfill stability and settlement analysis. The reasonable test results have an important influence on the leachate control and hydraulic analysis in the landfill.Artificial wastes with the same composition and physical index degraded quickly in a large self-developed degradation instrument under optimal conditions. Triaxial permeability method and conventional permeability method were provided to measure hydraulic conductivity of waste under different stress conditions during different degradation ages for the first time. The influence of the initial void ratio, degradation age, effective stress and test method on the hydraulic conductivity was investigated. The hydraulic conductivity of samples drilled from Chengdu landfill is measured by the triaxial permeameter and compared with the test results of artificial wastes. It was demonstrated that the saturated hydraulic conductivity of was significantly reduced with the increase of the effective stress or decrease of void ratio, the logarithm of hydraulic conductivity was approximately linear with the void ratio or the reciprocal of the effective stress. For wastes of the same void ratio, hydraulic conductivity was insignificantly reduced with the increase of degradation age. Test methods have a larger impact on the permeability of wastes, and the result from triaxial permeability test was lower than that from conventional permeability test. The hydraulic conductivity of artificial samples matched the result of filed samples, and the results can be applied to the practical engineering design and evaluation.Cellulose, lignin, organic compound, biological degradable material, chemical oxygen demand and pH from artificial wastes and leachate were tested every few months, and the purpose is to assess stabilization process of wastes. It was demonstrated that wastes of18months had degraded and been basically stable.Based on the concept of specific gravity, vacuum drainage method is proposed to measure the specific gravity of waste and the adverse factors on the test result are systematically analyzed. Some materials of which the specific gravity are known are tested. In comparison with other specific gravity test results, test results of vacuum dewatering method are thought alike with the theoretical values. This method is easy to operate, and the effect applied in the specific gravity of wastes is verified. Finally, this method is used to measure the specific gravity of wastes at different depths in the Chengdu landfill.