Experimental Study On The Evaluation Of Rock Damage Under Cycle Loading

Rock damage and evolution is the basic reason for rock material failure; it is significant to determine the damage state for the security of the rock engineering. The rock will damage under external load, accompanied by a series of changes in physical and mechanical properties. By testing the changes, we can determine the damage state of the rock and evaluate the damage degree. The damage state of rock can be determined with number of acoustic emission and velocity variation under uniaxial monotonous loading. We can evaluate the damage degree quantitatively with acoustic emission and velocity memory under cycle loading.In this paper, we use uniaxial monotonous loading and cycle loading to detect the acoustic emission and ultrasonic wave velocity synchronously in the process of rock damage, and make comparative analysis on the variation law of acoustic emission and velocity with damage. It shows that the rock damage process can be divided into several stages, and the acoustic emission and ultrasonic velocity variations exhibit different characteristics in different stages. The relative changes of ultrasonic velocity can be used to make stable and reliable identification of the rocks’"strengthen loading "and" weaken loading "; the value of b during acoustic emission is more sensitive to the non-stable expansion of the fractures and can be considered as a warning parameter of rocks’instability; Both the acoustic emission and the velocity have a memory in rock damage, and the acoustic emission and velocity variation under cycle loading can provide richer information on rock damage; Based on Felicity effect of acoustic emission under repeated loading conditions, we bring up a new parameter of rock damage’s quantitative evaluation-" reload ratio". We also come to the Kaiser effect error of core stress about geostress will increase with degree of rock damage, there demand damage correction. These results can be used to guide the emission measurements of core stress about geostress, rock damage’s quantitative evaluation and rock engineering’s safety evaluation.