Drilling-Based Rock Strength Estimation: A Validated Model for Mohr-Coulomb and a New Theoretical-Empirical Approach for Hoek-Brown Parameters

Conventional methods for determining the strength properties of rock are often costly and time-consuming. This research presents an innovative approach using operational drilling data for the continuous, real-time estimation of rock strength parameters for both the Mohr-Coulomb and Hoek-Brown failure criteria. The study evaluates a theoretical model for Mohr-Coulomb parameters and introduces a new theoretical-empirical model to estimate Hoek-Brown constants. These models were validated against conventional laboratory tests on ten different rock types, including sedimentary, metamorphic, and igneous varieties. The results demonstrate that the models can effectively estimate the strength properties for both failure criteria. A key finding is the introduction of a dimensionless ratio of bit diameter to rock grain size (D/d), which was shown to be a critical factor governing the accuracy of the Mohr-Coulomb …