The Use of Hoek Brown Failure Criterion on Determination of the Geo-Mechanical Parameters of a Grouting Consolidation Body

In this paper, the mechanical parameters of the grouting consolidation body on the rock block are studied using the Acoustic velocity test case and the revised Hoek-Brown failure criterion in underground metal mines. In light of the hidden resources in the collapsed area of the underground metal mine, the intact rock drilling core cannot be obtained to perform the mechanical test because of extreme damage or because it is completely broken. Therefore, pure cement grouting is used to reinforce the extremely broken rock mass within the collapsed area of the hidden resources. The RQD value and water permeability are tested to indicate that cement pastes can fill the cracks in broken rock blocks and can improve the integrity of the broken rock mass. To detect the grouting consolidation effect of the fractured rock mass and evaluate the mechanical parameters of the consolidation body, a nondestructive test is applied to measure the Acoustic velocity of the consolidation body after grouting. Initially, the measured Acoustic velocity is adopted to calculate the damage index (or integrity index), which is approximately equivalent to the disturbance factor. Then, the modified Hoek-Brown failure criterion is used to evaluate the mechanical parameters of the grouting consolidation body. Finally, to verify this method, the mechanical parameters of the rock mass are also obtained by a laboratory test. The outcomes show that the current research can serve as a practical method when evaluating rock mass quality by the grouting treatment.