Study on crack propagation of rock bridge based on multi parameters analysis of acoustic emission

Abstract

In order to study the characteristics and failure mechanism of crack propagation in open rock bridge， the uniaxial compression tests with AE monitoring system were conducted on specimens with granite bridge. The crack propagation process was analyzed according to the stress-strain curve and the parameters and spectrum characteristics of AE results. The results showed that the crack was initiated from the tip of the prefabricated crack and its direction was controlled by the stress direction. The phenomena of pre-peak fluctuation rise and post-peak ladder descent occurred in the stress-strain curves. The sudden increase point and relatively calm period of AE count rate and energy rate appeared intermittently and the cumulative count rate and cumulative energy curves rose in steps. Each point of sudden increase corresponds to the formation of a macro-crack，and the energy for the propagation of macro-cracks was accumulated in the relatively calm period. The AE spectrum was more sensitive to the crack propagation. The high frequency and low amplitude and the low frequency and low amplitude signals corresponds to the inter-granular cracks or trans-crystalline micro-cracks. The high frequency and high amplitude signals corresponds to the mesoscale cracks or small scale trans-crystalline cracks. The low frequency and high amplitude signals corresponds to the macro-cracks. The middle frequency and low-amplitude signals are related to the friction of existing section.