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Title Simulating acoustic emissions in bonded particle models of rock

Authors J.F. Hazzard, R.P. Young

Publication Reference 2000, International Journal of Rock Mechanics, 37, 867-872

Abstract Recording AE during laboratory testing of rock samples can provide significant additional information on the micro-mechanics of failure processes [1]. Information about the onset and propagation of microcracking and fracture in rock samples subjected to different stress regimes can be determined by recording the time and location of AE during the test. Using AE to map out fault nucleation and propagation may also be useful in the understanding of earthquake mechanisms and may contribute to solving the problem of earthquake prediction [2].

As well as monitoring spatial and temporal patterns of microcracking, recording full-waveform information for AE enables the calculation of source characteristics such as magnitude and mechanism [3,4]. Furthermore, it has been shown that AE amplitudes obey the power law frequency-magnitude relation observed for earthquakes [1,5].

An area of research that is less well-developed is numerical modelling of acoustic emissions. Several numerical models have been proposed to simulate cracking and failure in brittle rock specimens [6, 7, 8] however none of these models account for energy released during crack formation (i.e. seismic waves). In this Technical Note, a two-dimensional ‘bonded-particle’ model of rock is proposed where the rock is simulated by an assembly of circular disks with specified stiffnesses connected by bonds of specified strengths. With this model, strain energy can be stored at the particle contacts until the bond strength is overcome, at which time the bond breaks and the stored strain energy is released as kinetic energy in the form of a seismic wave. These ‘bonded-particle’ models have been used successfully to simulate brittle rock behaviour in previous experiments [9] however acoustic emission information was not recorded. This Technical Note presents a technique for recording acoustic emissions in bonded-particle models and applies the technique to a simulated compressive failure test on a model of a granite core sample.

Key Figure Key Figure
AE occurring before (left) and after (right) the peak stress. AE consisting of 3 or more cracks are plotted as best-fit ellipses. One ellipse is shown with the crack locations to show the quality of the fit.

Link http://www.sciencedirect.com/science/journal/13651609



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