Damage quantification of intact rocks using acoustic emission energies recorded during uniaxial compression test and discrete element modeling

In this paper, acoustic emission (AE) energies recorded during 73 uniaxial compression tests on weak to very strong rock specimens have been analyzed by looking at the variations in b-values, total recorded acoustic energy and the maximum recorded energy for each test. Using 3D Particle Flow Code (PFC3D), uniaxial compression tests have been conducted on discrete element models of rocks with various strength and stiffness properties. An algorithm has also been used to record the AE data in PFC3D models based on the change in strain energy upon each bond breakage. The relation between the total released acoustic energy and total consumed energy by the specimens has been studied both for the real data and numerical models and as a result, a linear correlation is suggested between the released AE energy per volume and consumed energy per volume of the intact rocks. Comparing the recorded acoustic energies in numerical models with real data, suggestions are made for getting realistic AE magnitudes due to bond breakages (cracks) from PFC3D models by proposing a modification on Gutenberg–Richter formula that has been originally proposed for large scale shear induced earthquakes along faults. Also, using the numerical model, an attempt has been made to quantify the damage to the intact rock by proposing a damage parameter defined as the total crack surface observed during the tests divided by the total crack surface possible based on size of particles.