Shaking Table Test On Seismically Induced Deformation Mechanism And Seismic Stability Evaluation Of Municipal Waste Landfills

Seismic stability evaluation of municipal waste landfill is a new challenge in environmental geotechnology. Due to lack of understanding seismically induced deformation mechanism, seismic stability analyses of landfills are commonly performed using the methods developed to analyze earth embankments. Physical model experiments of landfill are conducted on shaking table in this thesis, then, based on analyzing earthquake failure mechanism of landfills, theoretical studies are performed, in order to develop the special methods for seismic stability evaluations of landfills.The main research results of are as followed:1. According to the typical landfill configuration, 8 physical models are designed, and the following conclusions are drawn from shaking table test:(1) Experiencing excessive relative displacement within the specific interfaces of landfill liner and cover systems is the primary observed failure patterns induced by earthquake, however, waste itself collapse is seldom a concern problem.(2) When other parameters are fixed, seismically induced permanent displacement of landfill liner are shown to be approximately proportional to the amplitude of input motion.(3) Significant acceleration attenuation of motion took place when earthquake wave transfer through landfill base liner which including HDPE geomembrane, moreover, the attenuation is more obvious, while the peak acceleration of input motion is larger.2. Nonlinear numerical simulation of Landfill models using in shaking table test is conducted, in order to supplement verification of the physical model test results and be prepared to validate the proposed stability evaluation method.3. On supposing that the potential sliding mass above landfill base liner are constituted of three rigid blocks, a formulation, to estimate the yield acceleration of landfill base liner approximately, is presented by limit equilibrium analysis. Based on analyzing seismically induced deformation mechanism of landfills, the Horizontal Equivalent Acceleration (time-history) HEA_c(t) and MHEA_d(t) are defined at landfill top cover slop and base liner respectively. Nonlinear numerical calculation of the landfill models indicates that the Maximum Horizontal Equivalent Acceleration MHEA_c and MHEA_d can represent the loading level induced by earthquake. The process of pseudo-static analysis to evaluate the earthquake stability of 2D landfill is given. 4. Energy dissipation and transfer of frictional slip surface between two rigid blocks are investigated; then, an energy balance equation is formulated for NewMark sliding-block model. Theoretically, an approximate linear relationship between the energy coefficient e vs (ky/ka)~2 is found when the relative displacement in the interface get the maximum value with sine wave input. Considering the approximate linear relationship, statistical analysis of earthquake-induced permanent displacement data, which are results from. NewMark sliding-block model numerical calculation, is conducted, and a Simplified formulation for predicting the earthquake-induced displacement of landfill is presented, Comparison with other earthquake-induced permanent displacement fomulas in literature indicates that calculating results using the proposed formulation is reasonable, and can be used in practice more easily.5. 2D seismic response of landfills with typical geometry configuration is explored in detail, in order to investigate seismic response characteristics of landfills, as well as to study how the factors, including wastes properties, landfill heights, input motion and site conditions, to influence top acceleration response of landfills. With the Maximum Horizontal Equivalent Acceleration (MHEA_d and MHEA_c) representing the loading induced by earthquake in landfill deep liner system and cover system respectively, the stability of landfill is evaluated. As an engineering application example of the formulation (5.29) and (5.30) suggested in this thesis, the permanent displacement induced by earthquake of the most dangerous case.6. A finite difference analysis using the computer code FLAC is conducted of tension in landfill HDPE geotechnical membrane under complicated loads. The main conclusions are: (1)the accumulative tensile stress is developed in HDPE membrane by waste dumping, differential settlement, and earthquake. (2) the differential settlement effects the stress in liner HDPE membrane primarily. (3) the tensile stress in cover system HDPE membrane is higher than ultimate strength of HDPE geotechnical membrane under moderate intensity motion input (eg peak acceleration is 0.25g)...