Evaluation of the Integrity of Deep Rock Masses Using Results of Digital Borehole Televiewers

Abstract

Rock mass integrity is regarded as an important index to evaluate rock mass quality. Core drilling technology is one of the effective methods used for this. To overcome the problem of core discing and core breakage from the drilling process, a new evaluation method was proposed: a rock mass integrity index (RMIBT) based on high-definition digital borehole televiewer data. The RMIBT values were obtained by measuring the mass proportions of the length of the rock mass without macroscopic fractures on the borehole wall. Their scoring criteria were determined based on rock quality designation. It was applied in multiple deep rock excavations and therefore proved to be useful, especially where core discing occurs, in specific spatial distributions of structural planes, as well as logging errors from core breakages induced by drilling. In addition, the RMIBT can be used to assess dynamically the integrity of macroscopic rock masses and the evolution of fractures in the excavation damaged zone, thus providing a basis for the evaluation of rock masses in deep rock excavations.