ABSTRACT

: Falls of ground by buckling induced failure mechanisms can be a typical failure mode in highly stressed, laminated ground. A case study is presented in which the performance of ground support is back analyzed and evaluated for design improvements using numerical modelling. The case study is for a tabular ore body exploited over a single mining horizon, where well-developed, horizontal jointing is present. The depth of the horizon is relatively shallow (less than 200 m) however the region has high horizontal stress. The rock bolt ground support was originally designed for static loading conditions (gravity driven instabilities). Where falls of ground occurred, the compromised bolts clearly exhibit tensile failure. However, by static loading kinematics, their tensile capacity was far greater than the dead weight load of the failed rock volume. Analysis indicated that high horizontal stresses drove buckling of the horizontal beams. This paper demonstrates a back analysis of rock-beam buckling and the failure of support elements using numerical modelling assessment. Model calibration is performed by analyzing these failure mechanisms to determine the critical geomechanical factors. The calibrated numerical models are then used to optimize the design of ground support.

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