Abstract

Micromechanical models of high porosity chalk and low porosity granite are presented to examine the mechanics of cracking and failure that occur in the rocks when they are subjected to stress. The models are run dynamically (with low numerical damping) to allow for dynamic fracture propagation and so that acoustic emission (AE) information can be obtained. Seismic parameters such as source location, magnitude and crack type are calculated internally within the models. It is also shown how it is possible to calculate this information externally through waveform inversion of synthetic AE. These methods are used to compare the acoustic behaviour of compacting chalk models with different porosities. It is shown that low porosity chalks are more seismically active than those with high porosities. The methods are also applied to observe the cracking and eventual macrofailure that occurs in axially loaded granite samples. The micromechanics of tensile cracks occurring during loading of the granite are examined directly by observing the particle motions at the source, and indirectly by recording waveforms and calculating seismic parameters.

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