A MSW Constitutive Model Considering Degradation Effects And MSW Negative Dilatancy Research

With Sustained rapid development of economy and the gradually promoting process of urbanization, followed by a rapid growth of municipal solid waste, the number of new landfill and expansion over the old landfill site is also increasing.Unlike the general soil, by reason of the high compressibility and high organic content of waste, degradation occur and cause considerable deformation with in the landfill process.In the landfilling process and subsequent deformation of MSW landfill, often causing damage to the pipeline,liner, cover layer, and thus easily lead to instability of the landfill body, leachate leakage, landfill gas diffusion and explosions and other disasters.Therefore, landfill design should consider the effects of deformation of MSW landfill on landfill appurtenances(gas collecting pipe, leachate collection pipes, liner, cover layer), which usually requires the use of numerical methods for computational simulation.This thesis briefly expound the characteristics of MSW such as degradation, stress-strain releationship, strength, and pointed out that MSW has negative dilatancy evident. Some scholars use traditional mechanics constitutive model of soil or create a new constitutive model applied to the unit body and MSW landfill engineering numerical simulation.This thesis summarizes the MSW constitutive model and are classified as follows:one class of model is built on the basis of incremental elastic theory, which has not consider long-term degradation effect and also the negative dilatancy. Another class of model is based on the elastic-plastic theory, theoretical model is relatively complex and is not convenient for engineering application.This thesis carried out the research for the purpose of the constitutive model conducted on MSW deformation constitutive model for the long-term goal to study and consider the short-term deformation negative dilatancy completed the following studies:1) Giving a detailed description for volumetric strain and axial strain of the physical processes of MSW for MSW unit body under stress and degradation coupling effects. And based on the results of previous studies, proposed a series of basic assumptions for the coupled stress degradation process;2) Based on the MSW unit stress degradation model physical process and The basic theory of hypothesis, established a nonlinear constitutive model for municipal solid waste considering effect of degradation;3) With proposed MSW constitutive model which considering effects of degradation to simulate the consolidation drainage stress-strain relationship curves of of the field sampling, simulate the indoor unit cell one-dimensional long-term degradation of compression test, preliminary showed that the the proposed model can simulate triaxial stress-strain relationship for MSW sample of different age and the the degradation coupling process of one-dimensional compression for a long time.4) Based on negative dilatancy of MSW, came up with the nonlinear elastic constitutive model equations which consindering negative dilatancy, and gives examples to verify the primary compression, and also put forward the basic ideas of unloading equation.