Experimental study on shear strength parameters of fresh municipal solid waste

To investigate the laws of the shear strength parameters of fresh municipal solid waste (MSW), the compression-direct shear combined tests are carried out by using large-scale combined test apparatus of compression and direct shear. Two hundred and eighty-eight fresh MSW testing samples are prepared in geo-environmental laboratory. The components of fresh MSW are divided into three parts, and three mixture proportions are given to simulate the three stages of urban economic development, which are underdeveloped, developing and developed. The initial void ratios of the samples are selected as 2.1, 2.5 and 2.9. Four different vertical pressures, 25, 50, 100 and 200 kPa, are chosen, and the compression time for every vertical load is 0, 0.25, 0.5, 1, 2, 6, 12 and 24 hours, respectively. The shear strength parameters for ten different shear strain limit values, which are 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% and 20%, are studied. The test results show that the relationship between the shear strength and the vertical load applied on the test samples is in conformity with the Coulomb’s law. Besides, the cohesion force and the internal friction angle of the fresh MSW increase with the increase of the shear strain limit value, and a logarithmic model can be used to describe the relationship. Furthermore, the shear strength parameters of the fresh MSW under various conditions are obtained. It is found that the cohesion force varies from 6.14 to 34.17 kPa, and that the internal friction angle varies from 4.1 to 30.6 degrees.