Mining of Mineral Deposits

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Rock slope stability analysis using shear strength reduction technique (SSRT) – case histories

Wael R. Abdellah1, Mamdouh Y. Hussein1, Said S. Imbabi1

1Assiut University, Assiut, 71516, Egypt

Min. miner. depos. 2020, 14(2):16-24

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      Purpose. This study aims to evaluate the slope stability of open pit comprising massive and jointed rock mass.

      Methods. Mohr-Coulomb yield function (MC) with shear strength reduction technique (SSRT) are incorporated in finite element analysis (FEA) and four different slopes with varying geometry and geological structural features with an ultimate slope angle of 34° are analyzed using the two-dimensional FEA Program RS2D. The first slope comprises blocky rock mass; the second slope has a network of joints parallel to slope face; the third slope has a parallel joint networks dip out the slope face, and the last slope has a cross-joints network.

      Findings. The critical strength reduction factor (CSRF) indicates whether the slope face is stable (if CSRF ≥ 1) or not. The minimum CSRF of 0.53 (e.g. compared to 0.55 for parallel joints dip out to the slope face, 0.58 for joints parallel to slope face and 0.65 with no joint existed) is obtained with cross-joints network existed. The CSRF (e.g., CSRF = 0.49) reduces when the MC slip criterion is adopted with the jointed rock mass.

      Originality.This study attempts new stability indicator namely critical strength reduction factor (CSRF) embedded in shear strength reduction technique (SSRT), based on finite element (FEM) to assess the slope of open pit with respect to presence of geological discontinuities.

      Practical implications.The slope stability of rock mass is significant to design parameters in open pit mines. Unexpected instability is eventually costly, hazardous to personnel/machinery, disrupted to the mining operation and time-consuming. Therefore, this study Provides a methodology for the application of shear strength reduction technique (SSRT) when eva-luating the slope stability of open pit mines with respect to existence of geological features. As a result, the mine planners and engineers will be able to know a head of time when and where necessary support is needed.

      Keywords: open pit slope stability, shear strength reduction technique (SSRT), factor of safety (FS), critical strength reduction factor (CSRF)


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