Experimental study of the mechanical behavior of oriented bimrocks under diametral compression test using DIC

چکیده مقاله

Block-in-matrix rocks (Bimrocks) are complex geomaterials consisting of strong rock blocks embedded in a weaker matrix, exhibiting highly heterogeneous mechanical behavior. Understanding their mechanical properties—particularly tensile strength and fracture mechanisms—remains challenging for geotechnical engineers in design of surface and underground structures. The orientation of rock blocks, which forms during Bimrock genesis, can significantly influence their mechanical behavior. This study investigates the effect of block orientation on the tensile response of Bimrocks using diametral compression (Brazilian) tests, supported by digital image correlation (DIC) to analyze strain localization, crack initiation, and propagation patterns. Synthetic Bimrock specimens with controlled volumetric block proportions (VBP) and block orientations were prepared and tested. Given the material’s heterogeneity and data scatter, response surface methodology (RSM) and analysis of variance (ANOVA) were employed for statistical evaluation. Results indicate that the peak load decreases sharply from pure matrix specimens to those with 12.5% VBP, followed by a slower decline at higher VBPs. Increasing block orientation relative to the loading direction significantly enhances peak load resistance, particularly at higher VBPs. DIC analysis revealed that higher VBPs promote crack initiation away from the disc center, with multiple strain localization zones observed at 50% VBP. The study demonstrates that the Brazilian test yields invalid tensile strength estimates at high VBPs, and even at low VBPs, results depend critically on block size and orientation. These findings underscore the anisotropic tensile behavior of Bimrocks and highlight the limitations of conventional testing methods for heterogeneous materials.