Undrained Response of Municipal Solid Waste Collected from a Waste Site in Delhi, India

Consolidated undrained triaxial compression tests with pore water pressure measurement were carried out on 150-mm-diameter samples of municipal solid waste (MSW) recovered from a waste site in Delhi. While understanding that the mechanical response of municipal solid waste has evolved significantly in the recent years, most of the previous work has studied the behavior of MSW under drained conditions. However, there are several situations in which the undrained behavior of MSW may be important, particularly for uncontrolled dumps and bioreactor landfills where the MSW may be in a saturated or near-saturated condition. MSW samples were reconstituted at their in-situ composition and reconstituted with only a less-than-20-mm fraction (the soil-sized fraction) for comparison. The stress strain response of specimens at the in-situ composition showed a strain hardening type behavior, with the mobilized shear strength continuing to increase without reaching peak strength at strains in excess of 20 percent. Specimens with only the soil sized fraction exhibited a peak response, clearly demonstrating the role/importance of fibrous waste constituents in the mechanical response of MSW. In both cases, shear strength parameters established based upon several different failure strain criterion indicated an effective friction angle in excess of 45 degrees.