Experimental investigation of mechanical damage and acoustic emission characteristics of tuff under triaxial compression

In this study, mechanical properties of saturated tuff with different weathering degrees under confining pressures of 0, 0.5, 2.5, and 5.0 MPa are systematically investigated by laboratory experiments with the aid of acoustic emission (AE) technology. Results reveal the influences of confining pressure and weathering degree on mechanical behaviors of saturated tuff, including elastic modulus, Poisson’s ratio, compressive strength, damage evolution, and failure mode. As the confining pressure builds up, the compressive strength and elastic modulus of the specimens increase linearly, the peak strain, deformation capacity and residual strength also increase apparently, and the ductile failure becomes more significant. The stress-strain curve at the initial loading stage shows a compaction segment, which becomes more prominent with the increase of weathering degree. AE data show that the fracture process of saturated tuff under triaxial compression can be divided into three stages: microcrack initiation stage, microcrack propagation stage, and macrocrack formation stage. In the fracture process of saturated tuff, the damage evolution is distinct. Based on the experimental results, a theoretical model of the stress-strain relationship of saturated tuff, which has taken into consideration various confining pressures, is constructed using the elastic-plastic theory.