Approximated calculation model for plastic deformations of granular waste materials

Abstract

This paper suggests an approximate model to estimate the total plastic deformation of layers made of granular materials. In this work, the model was designed to calculate the plastic deformations of the cylindrical specimen of monotonic triaxial tests. The model concept is based on the deformation mechanisms of granular material presented in the literature review. These mechanisms assumed that the volume of the whole granular material structure decreases because of particle rearrangements and compressibility of the materials. In triaxial tests, there are three main stages of loading and deformations. A plastic deformation begins in the material due to the post-compaction and tamping effects of the initial loading. This deformation results from compression of the fine material coating between the particles completely or partially depending on its degree of compressibility expressed, herein, by a hardness coefficient. At further loads, the particles contact directly each other and the sample behaves elasticity. When resultant forces on the particle at high levels of loading are more than the confining pressure and shear strength of the material, the particles move or slip laterally causing damage and buckling. The model estimates the total vertical deformations of the material as the sum of the deformation resulting from the post-compaction process and those generated from the re-orientation and horizontal movement of the particles. The model was validated with the results of monotonic triaxial tests of untreated and treated blends made of limestone and Incinerator Bottom Ash Waste (IBAW) to examine the effect of various material properties on the model calculation accuracy. The model results showed that the approximation model depicted the experimental value of the plastic deformations fairly well as the error parentage ranged between 12% and −15% for treated and untreated blends.