ABSTRACT:

Municipal Solid Waste (MSW) is a refuse composed of various materials with different properties. Some of the components are stable while some degrade as a result of biological and chemical processes. These aspects impart to MSW a complex behaviour that has been modelled, with many limitations, considering the concepts of soil mechanics. In this paper, a framework to model the MSW mechanical behaviour is proposed, based on results from laboratory tests, such as triaxial compression and confined compression on large samples. It is admitted that the MSW mechanical behaviour is commanded by two different effects:

  • the reinforcement of MSW by the fibres (composed by many types of polymers) and

  • the behaviour of the MSW paste, without the fibres.

Accordingly, the MSW behaviour was also divided into two distinct parts:

  • a critical state framework for the MSW paste and

  • an elastic perfectly plastic framework for the waste fibres, with a time lag for fibre solicitation (function ÒfmÓ).

The proposed model was capable of reproducing quite well the results of the triaxial and confined compression tests.

INTRODUCTION

Difficulties in studying and modelling municipal solid waste are associated to the heterogeneity of the material, which presents different types and dimensions of constituents and has components that degrade with time, generating leachate and gas. The biodegradation of the organic waste and physicalchemical processes contribute significantly to modify the strength and compressibility behaviour of the waste. Moreover, there are difficulties related to sampling, types of tests and sizes of specimens more suitable to the MSW study. For instance, it is known that shear strength parameters (cohesion and friction angle) can be defined only as a function of strain since failure cannot be observed even at high sample compression (Singh & Murphy, 1990; Jesseberger & Kockel, 1993; Jesseberger et al, 1995).

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