Passive tomography to image stress redistribution prior to failure on granite

Abstract

Understanding stress redistribution within rock helps improve the safety and efficiency of mining projects. In order to better understand rock failure mechanism, a granite sample is prepared in a manner that facilitates shear failure along preconceived cracks. The testing process of this method employed several steps. First, the sample is loaded and then monitored in order to study the stress field associated with shear failure. Passive acoustic emissions systems are then used to monitor seismic events during the loading process. The data obtained from the test is processed by using the double-difference location algorithm. The velocity pattern of the sample is then calculated. The distribution of velocity is projected using double-difference tomography. It is shown that the sample failed along the plane where two parallel cracks were prepared. Most of the relocated events were located within or around the plane. The tomograms created from the recorded data accurately image the areas of interest within the rock samples. It is also shown that passive acoustic emissions monitoring systems coupled with double-difference tomography are capable of monitoring and forecasting the failure of rock.

Keywords:

• double-difference tomography
• granite
• acoustic emissions system
• velocity model
• stress redistribution

Acknowledgement

The authors gratefully acknowledge the China Scholarship Council for their support of this project – File No. [201206430030].