Strength Behavior of Jointed Rock Mass at the Crown of the Slope

Assessments of failure mode and strength behavior of unconfined anisotropic rock mass are difficult due to variations in the joint orientation, joint frequency, and intact rock properties. Load-bearing capacity of such rocks may vary from 0 to 600 MPa. Therefore, its strength assessment is necessary for designing the foundation of any structure constructed near the crown of a slope-like foundation on a river bank/hilly area. This study assesses the strength characteristics of such rock mass under unconfined conditions at the crown of the slope through physical model testing. Rock samples were used to model a rock mass test specimen, which is comparable with the field. Experimental results could be compared to the field because of large number of joints in one test specimen. One test specimen required 1500–2000 cuboidal elements dimensioning 25 × 25 × 75 mm. In this study, the failure modes of side slope due to external distributed load at the crest were evaluated. To this end, a physical model was prepared as 75 × 75 × 15 cm in the lab and joints and side slope angles were considered varied 15° from 0° to 90°. Among this procedure, a methodology to predict the load-bearing capacity of rock mass was proposed. Lastly, the failure mode and settlement of side slope were verified based on the numerical simulation using finite element method (Phase2). The results have shown the predicted load-bearing capacity from the suggested approach, gives the reliability of ± 20%.