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The characteristics of municipal solid waste (MSW) play a key role in many aspects of waste disposal facilities and landfills. Because most of a landfill is made up of MSW, the overall stability of the landfill slopes are governed by the strength parameters and physical properties of the MSW. These parameters are also important in interactions involving the waste body and the landfill structures: cover liner, leachate and gas collection systems. On the other hand, the composition of the waste, which affects the geotechnical behavior of the MSW, is dependent on a variety of factors such as climate, disposal technology, the culture and habits of the local community. It is therefore essential that the design and stability evaluations of landfills in each region be performed based on the local conditions and the geotechnical characteristic of the MSW. The Bandeirantes Landfill, BL, in São Paulo and the Metropolitan Center Landfill, MCL, in Salvador, are among the biggest landfills in Brazil. These two disposal facilities have been used for the development of research involving waste mechanics in recent years. Considerable work has been made in the laboratory and in the field to evaluate parameters such as water and organic contents, composition, permeability, and shear strength. This paper shows and analyzes the results of tests performed on these two landfills. The authors believe that these results could be a good reference for certain aspects and geotechnical properties of MSW materials in countries with similar conditions.

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Organic soils represent accumulations of disintegrated plant remains that have been preserved under condition of incomplete aeration and high water content. Using electrokinetic (EK) techniques to improve organic soils entails evaluating factors that define geoenvironmental behavior of organic soils. Electroosmotic properties were investigated to conceptualize EK phenomena. The results of the study showed that the zeta potential, specific surface area, water contents, and liquid limit (LL) increased as the organic content increased. The natural zeta potential of the organic soils varied from −11.2 to −20.8 mV according to the organic content, degree of humification, and soil pH. The negative charge in organic soils is highly pH dependent and surface charge is dropped to zero at pH 2.3 to 3.5. The greater degree of humification resulted in the higher zeta potential and lower pH at the iso-electric point. This paper also gives some insights on ionic modification, which is an innovative method that could be employed to change the water holding capacity of organic soils and its consistency. The Fe+3 ions had 20 to 30% pronounced effect on decreasing LL according to the organic content. Increasing the cation valence reduces the affinity of water to the organic soil surface and decreases LL as a major part of Atterberg's consistency system. By the sound of peat and its environment, there is a great likelihood that EK techniques could be used to resolve peat's difficulties from the geoenvironmental viewpoint.

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Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids (D 50,r /D 50,s ) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10 −4 % to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D 50,r /D 50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.

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