Upper Bound Stability Analysis of Rock Slopes Considering Hoek-Brown Failure Criterion

Rock slopes are commonly more stable than soil slopes when subjected to different types of external loadings. Despite the fact that rock masses are commonly stronger than soils, stability analysis is necessary even for rock slopes, since any failure of them may result in a huge loss of lives and wealth. In the present paper, upper bound method of limit analysis is employed for stability analysis of rock slopes obeying Hoek-Brown failure criterion. In many previous studies based on the upper bound method, the nonlinear Hoek-Brown criterion was linearized using a single straight line which resulted in reducing the accuracy of the obtained results. For improving the accuracy of the factor of safety of Hoek-Brown rock slopes, the present paper proposes a multi-tangential technique for linearizing the Hoek-Brown criterion, in which, the nonlinear criterion is replaced by several tangential lines to the main nonlinear criterion. This method results in improving the accuracy of the obtained factor of safety. Using the obtained results, the effect of different important parameters on the factor of safety of rock slopes can be evaluated. Increasing the uniaxial compressive strength of intact rock, Geological strength index and the Hoek-brown constant mi results in increasing the safety factor, while increasing the disturbance factor and the rock mass density, the slope height and the slope inclination results in decreasing the safety factor. Finally, simple charts are presented which are useful for quick determination of factor of safety and stability number of rock slopes in practical applications.