Size-Dependent Hoek-Brown Failure Criterion

The size dependency of intact rock is of importance to different disciplines, such as civil and mining engineering. One example relates to the design of structures on or within a rock mass for which an estimation of the strength of the intact rock blocks within the mass is essential. Despite a large number of studies on size effects in rock, less research has investigated size effect under triaxial conditions. Thus, a suite of advanced triaxial compressive experiments was conducted on Gosford sandstone samples with diameters of 96, 50, and 25 mm. A size-dependent Hoek-Brown failure criterion was developed by incorporating a unified size-effect law into the original Hoek-Brown failure criterion. The model was calibrated against the triaxial data obtained from Gosford sandstone. It was shown that there is good agreement between the proposed model prediction and the experimental results. Finally, an example of application of the size-dependent Hoek-Brown failure criterion was presented to demonstrate its versatility.