Thermo-mechanical volume change behavior of municipal solid waste: experimental study and constitutive model

Abstract

This paper investigates the thermo-mechanical volume change behavior of municipal solid waste (MSW) by conducting drained heating–cooling tests at constant stresses and isothermal consolidation tests using a temperature-controlled triaxial apparatus. The experimental results show that the compression and swelling indexes of MSW specimen were temperature independent, and the heating-induced volumetric contraction was partially reversible upon cooling. Different from conventional soils, the thermally induced reversible and irreversible volumetric strains of MSW were much larger and stress level dependent. Apart from the experimental study, an isotropic thermo-elastoplastic constitutive model was developed in the framework of existing modified Cam-clay model, which allows the prediction of thermally induced volume changes of MSW. An important feature in this model was the derivation of thermally induced plastic volumetric strain based on the concept of equivalent stress. The capability of the proposed model was validated against the experimental results and showed good predictions. This paper serves as the first attempt to study the thermo-mechanical volume change behavior of MSW, and has provided additional data for the serviceability evaluation of existing pipes as well as settlement and capacity estimation of MSW landfills at elevated temperatures.