Laboratory Study on Dynamic Properties of Municipal Solid Waste in Saravan Landfill, Iran

Abstract

Saravan landfill, located in northern Iran, has been an environmental cause of concern through its entire time of operation. As part of a project aimed at bringing the landfill conditions closer to standards, large-scale cyclic direct shear and bender element tests were carried out on reconstituted waste samples, obtained from different locations and depths at the landfill. Samples obtained at greater depths were found to have a higher fibre content which mostly consisted of nondegradable plastics that accumulated while a large part of the rest of the waste succumbed to biodegradation. Bender element tests showed an increase in the shear wave velocity and maximum shear modulus of the waste with ageing. This increase coincided with an increase in the sample unit weight. Normalized shear modulus reduction and damping ratio curves were obtained from the cyclic direct shear tests which were consistent with data available in literature. In addition, ageing was observed to shift the modulus reduction and damping curves to the left, decreasing the former while increasing the latter and resulting in a reduction in the shear strain corresponding to the onset of plastic behaviour. Ten cycles of direct shear loading at a 3.33% strain caused shear modulus and damping ratio to decrease by about 50% and 40%, respectively, most of which occurred within the first three or four cycles. Secant friction angle obtained from post-cyclic shear strength tests were found to vary between 32° and 55°, which was consistent with previous research.