Study On Stress Path Tests Of Municipal Solid Waste Combined With The Image Processing Technique

With the rapid development of economy and the sustainedly promoting process of urbanization,the production speed of municipal solid waste is growing by leaps and bounds.How to dispose MSW efficiently and safely becomes one of a very relevant concern recently in our country’s urbanization.Landfill,which now accords most with the situations and regional conditions of our country,will certainly be the mainstream mode of the future for a long period of time.Different from other geotechnical structures,the structural system of landfills is much more complex.The mechanical characteristics of the waste body inside are always in a dynamic condition with the influence of composition,age and humiture,etc.The high compressibility and degradability of MSW will also cause considerable deformation in the process of landfill.From the above,the environmental geotechnical problems in landfill bring great challenge to MSW dispose in our country.The problems of landfill settlements and the failure of waste slopes are closely related to the strength and deformation characteristics of waste body.Therefore,the study in constitutive relationship of MSW is very essential and necessary.In this thesis,the image processing technique is introduced in tri-axial compression tests of MSW for overcoming the shortage of the current experimental researching methods.Various stress path tests are carried out,and a constitutive model which can consider the effect of p-q coupling effect and the influence of stress path is established based on the tri-axial test results.Furthermore,the influence of rainfall infiltration in waste body is simulated through tri-axial tests to study the instability of MSW samples.The following studies are completed in this thesis:1.The feasibility of the application of the image processing technique in MSW tri-axial test is discussed.A method is designed to directly fetch the physical dimension of MSW samples in images.The error caused by the low saturability and inproper assumptions of samples can be avoided when using this method.2.Different stress path tests combined with the image processing technique are carried out to analyze the strength and deformation characteristics of MSW.Dilatancy characteristic and the Roscoe surface are observed from the stress path tests.Shear strain is stress-path-related according to the tests.3.A path dependent non-linear model which can consider p-q coupling effect is established based on the stress path tests results.The stress-strain characteristics of MSW in different stress paths can be described precisely using the proposed model.A tri-axial consolidated drained test result is predicted to verify the rationality of the proposed model.4.The instability of MSW is studied based on the tri-axial consolidated undrained test and the constant shear stress test results.MSW samples will become unstable when the effective confining pressure reduce to a certain proportion.The detail phenomemon depends on the sample’s composition.