An Experimental Approach to Evaluate the Role of Rock Failure Modes in Mechanical Characterization of Metabasalts

A detailed understanding on rock failure modes testifies the competence of support designs for engineering work. Studying such failure modes using physical models of rock specimens under laboratory conditions can be time efficient, informative and economically viable. In this study, the mechanical behavior of massive metabasalts were characterized with reference to rock failure modes through index tests such as point load and Brazilian tests. Rock failure modes under point load test are categorized as (1) single plane, (2) triple junction, (3) twisted and (4) single plane (inclined) failure modes. Twisted and triple junction failure modes are observed in the specimens with higher point load strength values (> 6 MPa). A total of five types of rock failure modes were observed in metabasalts under Brazilian testing conditions namely (1) central multiple, (2) central, (3) non-central, (4) central multiple + layer activation and (5) conjugate failure modes. Central multiple failure mode is found to be the most common failure mode in metabasalts due to their massive nature. Failure modes under Brazilian tests are observed within a range of 8 to 12 MPa. Among all other observed rock failure modes, single plane (inclined) and conjugate failure modes under point load and Brazilian tests respectively are introduced in this study. It is evident that rock failure modes controlling the strength of rocks should be considered as an important aspect for mechanical characterization of rock materials.