Building 3D models of rock strength using geophysical logs

Professor Peter Hatherly

Through a series of projects funded by the Australian Coal Industry Research Association (ACARP), we have developed a rock mass rating scheme for coal measure rocks which draws upon the compositional data contained within the geophysical logs as well as the sonic data. The scheme is known as the Geophysical Strata Rating (GSR) and our approach has some similarity to the method proposed by Barton for estimating Q-value from seismic velocity corrected for porosity and depth. As with other rating schemes, it also considers the properties of the intact rock mass as well as defects. These aspects of the GSR will be explained.

GSR data are obtained for the full length of each borehole. Data in this form can be used as input for the construction of 3D geotechnical models. For coal mining, we can extract information on key horizons and units so as to assist with decisions relating to bolting, caving and roadway stability. In this talk I will also provide examples of the use of the GSR in the construction of 3D geotechnical models.

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