Mechanisms and Measurements of Destressing in Underground Mines: A State-of-the-Art Review

Destressing and preconditioning of the rock mass through blasting or excavations is an important ground control technique that results in a release of stored energy and the generation of stress shadows in adjacent areas. The exact mechanisms involved in the process are still subject to debate, with the two main schools of thought proposing the creation of new fractures or slippage along pre-existing ones. Most authors currently agree that both result in softening the rock mass and reducing its stiffness, which leads to a stress decrease in the affected areas and their transfer into adjacent formations. Although different techniques have been reported in hard rock, coal, and caving operations, there has been a lack of comparative assessments with respect to geographical region, application depth, and operational purpose of destressing. In this study, a historical and geographical overview of destressing efforts spanning 75 years is presented, with key trends being underlined. This is followed by a review of the underlying mechanisms proposed and in situ measurements obtained. The objective is to compile a database of qualitative and quantitative changes in properties so as to develop a new approach for modelling the destressed rock mass. Summary tables are provided, listing mine sites, application depths, measurements of rock mass parameters, type of destressing, and operational purpose of implementing the technique. In the end, a summary figure is compiled of destressing techniques versus application depth based on the assembled database. The tables and figures underline key trends and can be used as an empirical reference for the design and application of destressing techniques, with several promising avenues for future research also suggested.