Estimating the geological strength index and disturbance factor in the Hoek–Brown criterion using the acoustic wave velocity in the rock mass

Abstract

The quantitative determination of the geological strength index (GSI) and disturbance factor (D) in the Hoek–Brown failure criterion is of great value because it can increase the reliability of the rock engineering design. In this work, a quantitative method for estimating GSI and D values is developed by considering the acoustic wave velocity in the rock mass, Cp. These improved GSI and D values are then used to propose a new method for determining the mechanical parameters of the rock mass based on the original Hoek–Brown failure criterion (which we refer to as ‘the improved Hoek–Brown failure criterion’). The analysis results show that the new method to estimate GSI and D can accurately reflect the factors affecting the rock-mass quality and degree of disturbance before and after blasting or excavation. The new method has high reliability and is also applicable to rock masses that are quite broken (i.e. have low Cp values). More importantly, the mechanical parameters calculated using the improved Hoek–Brown criterion for the rock masses involved in our case studies are in good agreement with the results obtained through long-term monitoring of the deformation. The veracity of the improved Hoek–Brown failure criterion was thus verified in a practical engineering context. Therefore, the proposed method can be used to rapidly determine the mechanical parameters of the rock mass when there is an insufficient amount of test data available.