Geotechnical characterization of the municipal solid wastes and investigation of their slope stability

Along with the developing world population generated municipal solid waste amount also increases day by day. Wastes have to be disposed safely for protection of human health and the environment. Sanitary landfilling has still been the most preferred disposal method. In order to dispose wastes healthily, safely and economically, waste material properties must be well defined. Uncontrolled waste storage, which is not with well defined engineering properties, not only causes economic loss, but also endangers human life and property safety. For this purpose, geotechnical properties of synthetic waste samples with pre-determined compositions and natural waste samples, which were gathered from landfill were investigated in the laboratory. In the tests, the effect of many parameters such as composition, aging, grain size, water content, and unit weight on the geotechnical properties of MSWs were examined. The synthetic MSW samples were collected to be representative of Turkey (T-1), United States of America (U-1) and the European Union (E-1) in average compositions and modified compositions, which were derived from these three basic compositions. Maximum grain size, natural water content, organic matter content, specific gravity and pH values of the synthetic and natural MSW samples were determined. Then, compaction tests were conducted under different compaction energies on the synthetic, natural and modified MSW samples, which have different grain size distributions. Compressibility behaviour of MSW samples were investigated by using a specially manifactured large scale compressibility test system in the C.B.U. Soil Mechanics laboratory. Composition and aging effect on the compressibility behaviour of MSW samples were also investigated on the saturated samples and samples having the optimum water contents. Shear strength parameters of synthetic and natural MSW samples were determined by using a specially manufactured large scale direct shear test system. The effect of grain size distribution, unit weight, composition, water content and aging were investigated on the shear strength behavior of MSW samples. Slope stability analyses were also conducted by using the obtained engineering parameters of MSW samples for present and designed slopes at static and dynamic conditions. Static and dynamic stability analyses were made by using Plaxis- 2D and Flac-2D computer programs. Maximum deformations and factor of safety values were obtained for the defined slope models. The evaulated MSW engineering parameters in this study can be used in the design of safe and economical landfills.