Experimental Study on Mechanical Behavior, Fracture Characteristics, and Acoustic Emission Damage Characteristics of Sandstone Under Triaxial Multistage Stress Disturbance

The instability failure of engineering rock mass is caused by the full development of cracks under the combined action of the surrounding rock stress environment and frequent stress disturbance. The development and propagation of cracks is essentially a process of cumulative rock damage and progressive failure. Taking the rock damage induced by crack development under multistage stress disturbance as the theme, combined with the engineering site, this work carried out multistage stress disturbance tests considering disturbance amplitude, time and initial stress factors, aiming at exploring damage mechanism of rock at each disturbance factor and the characteristics of microscopic crack development. The increase of various disturbance factors reduce the peak strength and average elastic modulus of the rock, and increase the axial strain increment at each disturbance stage, which weakens the mechanical properties of the rock. The microcracks development presents a process of "local convergence of microcracks to form damage zone, continuous development of microcracks to expand damage zone, propagation of damage zone to form fracture zone, propagation of fracture zone to form macroscopic fracture surface". Furthermore, the increase of the disturbance factors promotes crack development and expansion and induces the generation of tensile cracks. The established acoustic emission (AE) Qt value can reflect the development of microscopic cracks within the rock in real time and is negatively correlated with the rock damage state, which can be used as an index for quantitative evaluation of rock damage. The research results can provide some reference and guidance for the monitoring and evaluation of engineering rock mass damage. Conduct multistage stress disturbance tests of sandstone under triaxial compression.Analyze the effect of amplitude, time and initial stress on the mechanical behavior of rock.Explore the fracture characteristics and AE damage characteristics of sandstone.Reveal the damage and microscopic crack mechanism of rock under disturbance factor.