Abstract
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.
Highlights
Mechanical characterization of rock materials is considered to be the most important component in any engineering geology project (Diamantis et al 2009)
In order to access the role of rock failure modes in strength of the metabasalts, the different failure modes under the point loading condition and indirect tension were subsequently analysed and discussed further
The rock failure modes in metabasalts conspicuous in this investigation can be classified as Single plane failure mode, Triple junction failure mode, Twisted failure mode and Single plane
Summary
Mechanical characterization of rock materials is considered to be the most important component in any engineering geology project (Diamantis et al 2009). In line with this, Basu et al, 2013 documented the failure modes in granite, sandstone and schist under uniaxial compression, Brazilian and point load conditions and evaluated the relation between failure mode and mechanical strength of rock materials. The importance of point load testing in estimating the UCS as well as in geo-mechanical classification of rock masses have been widely discussed by several researchers in the past (Bieniawski 1975; Yin et al 2017; Xue et al 2020). The P-wave velocity was used to check the dependence of micro-flaws on the variation of point load strength index of the investigated metabasalts
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