Abstract
Analysis of rock wedge stability plays important role in tunneling and hard rock mining. Today there are many procedures for prediction of wedge formation and their stability. These procedures consider preexisting joints in rock mass, and there is no procedure that considers blast-induced cracks and their impact on structural stability of excavations. Using main principles of new rock blasting theory it is possible to assess length and density of radial cracks around blastholes. Herein, one simple excavation situation in hard rock is presented, where only two joint sets were present. This made it impossible for rock wedges to form. After blast-induced crack with limited persistence was added to analysis as result unstable rock wedge was formed. in addition to presented problem it is suggested how mechanical properties of blast-induced cracks could be estimated using Barton-Bandis failure criterion. As final result it was clear that without blast- induced cracks no wedge stability analysis is complete.
Highlights
INTRODUCTIONTheory describes formation of rock wedges by joint intersection and gives prediction of their stability
Torbica S., Lapčević V.Since it was introduced by Goodman and Shi (1985) key block theory found wide application in analysis of underground and surface excavations
Situation where excavation is done in rock mass where only two joint sets are present is analyzed
Summary
Theory describes formation of rock wedges by joint intersection and gives prediction of their stability. This made new approach for support design. Elmouttie (2010) develops the algorithm that is capable of handling curved, finite persistence joints for detection of the polyhedral rock blocks. Those procedures analyze rock wedge formation from preexisting joints in rock mass. There is no procedure that describes impact of blast-induced cracks on formation and stability of rock wedges in underground excavations. Focus is on explaining how blastinduced cracks may impact stability of underground excavations, and the fact that without blast-induced crack consideration no rock wedges analysis is complete
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