Shear strength behavior of mechanically-biologically treated waste in triaxial tests

To study the shear behavior of mechanically biologically treated (MBT) waste systematically, the samples from Tianziling landfill (Hangzhou, China) are collected, and several tests are carried out in an environmental and geotechnical laboratory, such as composition analysis, sample preparation, triaxial unconsolidated-undrained (UU), consolidated-undrained (CU), and consolidated-drained (CD) tests. These tests reveal that the main components of the MBT waste include plastics, textiles, glass, fines, and unidentified materials. The deviatoric stress gradually increases with the increasing axial strain, and no peak value is attained even when the axial strain exceeds 30%, indicating a strain hardening behavior. The UU, CU, and CD tests reveal the ranges of the shear strength parameters (cohesion force and internal friction angle). The relationship between shear strength parameters and axial strain is linear, and the fitting equations are obtained. The stress-strain relationship of the MBT waste conforms to that of the Duncan-Chang model, and the ranges of the model parameters (a and b) are obtained. Further, a power function relationship is established between the model parameters and the confining pressure. These results can provide a theoretical basis for the stability analyses of MBT waste landfills.