Resistência ao cisalhamento e permeabilidade de misturas de solo residual de basalto com resíduos da construção e demolição (RCD)

Abstract

The high rates of generation of construction and demolition waste (CDW) are alarming from an environmental point of view, as this waste is generally poorly managed and often improperly dumped on public roads, vacant lots and even in clandestine landfills, which favors the proliferation of disease vectors to human health and the deterioration of the environment. In the best-case scenario, i.e. if managed correctly, CDW will be sent to landfills and confined for future use. This practice is environmentally and economically damaging, taking into account the high cost involved in the management stages for the final disposal of waste in landfills, as well as the environmental impacts linked to the implementation, operation and closure of CDW landfills. Therefore, there is a clear need to know the geotechnical characteristics of CDW in order to provide the necessary technical framework for its use in engineering works. Thus, this study sought to investigate the behavior of a residual basalt soil, with emphasis on its permeability and shear strength, when adding CDW in contents of 0%, 20%, 40%, 60%, 80% and 100%. Variable load permeability tests were carried out at average hydraulic gradients of 7 and 10, and direct shear strength tests were carried out in drained and unsaturated conditions, at normal stresses of 100 kPa, 200 kPa and 300 kPa. There was a moderate variation in the permeability of the soil-RCD mixtures, with the highest and lowest permeabilities being in the order of 10 -5 cm/s and 10 -7 cm/s, respectively. The permeability determined for the pure waste was in the order of 10 -3 cm/s and the results of the permeability tests show that all the soil-RCD mixtures can be used for final cover layers in non-hazardous waste landfills. With regard to shear strength, the results showed an increase in the ultimate shear strength of the mixtures compared to the strength of the pure soil, as well as an increase in the internal friction angle of the soil and a decrease in the cohesion of the soil. Therefore, replacing soil fractions with CDW content in a range of 20% to 80% does not compromise its shear strength; on the contrary, it strengthens the soil and improves its shear strength parameters. Thus, the improvement in the shear strength of the residual soil shows that the CDW can be incorporated into this soil for applications in geotechnical works such as laying pipes for sanitation installations and sub-base for public sidewalks.