Influence of municipal solid waste composition on the shear strength of a landfill cell

The types of Municipal Solid Waste (MSW) present in landfills have the potential to promote variations in the shear strength of these sanitary masses. If this resistance is reduced, these works may become unstable, increasing the risk of slope failure. The consequences of failures are serious, such as the leakage of toxic gases and leachate into the environment, in addition to the cost of rebuilding the slopes. Therefore, this research aimed to determine the influence of each component of the urban solid waste on the shear strength of the sanitary mass. To this end, the MSW from a sanitary landfill was collected and its gravimetric composition was performed. Then, an inert and isotropic material, called basic matrix, was used in composition with waste (plastic, paper, cardboard, metal, glass, textile/leather, sanitary textile, wood, composite, organic matter and mixed material) to determine the shear strength of each component in a direct shear press. The results showed that waste such as paper, metal and wood exhibited a 22% reduction in the friction angle. Furthermore, no decreases in cohesion were observed for the waste. The study suggests that an increase in paper, metal and wood may reduce shear strength, impacting the reduction of the safety coefficient of landfills and exposing these works to greater risks of slope failure. The study reinforces the need for practices of reuse and/or recycling of the aforementioned waste, since the increase in these materials in landfills may promote reductions in the shear strength of landfills.