Abstract:
Process of failure in rock mass is extremely complex and engineers have a responsibility to estimate intact rock/rock mass strength and failure properties which define conditions under which failure will occur. If a criterion fails to fit the laboratory test data well enough than its applicability to real field cases would certainly be doubtful. Out of many failure criteria available today Hoek and Brown is one of the most widely accepted failure criterion within the rock mechanics community. The history and development of Hoek and Brown failure is reviewed in this research. The criterion has been modified over the period of time with incorporation of new parameters and integration of new rock mass classification system.
A comparison of Hoek and Brown criterion and few other commonly used rock failure criteria is carried out using tri-axial test data of variety of rocks. Test data of various types of rocks used for analysis is collected from Roc-Science database. It is found that for compressive strength, estimated results from failure criteria fits the laboratory test results reasonably well. However, the results for tensile strength are not satisfactory. There are certain uncertainties and ambiguities related to parameters estimation and clear guidelines are lacking. Different statistical tools were used to compare the results and to analyze the sensitivity of parameters. Analysis of individual data sets revealed that the estimated results are in good agreement with the experimental data for compressive strength but not for tensile strength.
