Field and numerical studies to evaluate slope stability in municipal solid waste sites

Shear strength properties of fibrous waste materials, which are found in most of landfill sites, play a significant role in the stability of side slopes of those sites. Recent records revealed that slope failures have occurred in several improper dumping and illegal landfill sites at some countries. Therefore, this paper introduces field and numerical studies to assess the shear strength properties of fibrous waste materials at locations of some municipal solid waste (MSW) sites. In the present study, shear response and shear strength of waste materials obtained from four different landfill sites were investigated using an especial developed in situ direct shear test apparatus. Moreover, the paper introduces the steps for preparation of undisturbed samples and test procedures in details to determine the in situ shear strength characteristics (c and phi) of MSW. The field experimental results indicated that the shear response of waste materials affected by the existence of fibrous materials contents in the MSW materials. In addition, the values of cohesion and friction parameters of waste materials strongly depend on the percent of fibrous materials. Furthermore, based on the field test results, numerical methods have been implemented in this work (i.e., FEM and LEM) to evaluate safety factors of side slopes, lateral and vertical deformations which usually occur during shearing and external loads.