Rock slope stability investigations in three dimensions for a part of an open pit mine in USA

Traditional slope stability analysis and design methods, such as limit equilibrium method and continuum numerical methods have limitations in investigating three dimensional large scale rock slope stability problems in open pit mines associated with stress concentrations and deformations arising due to intersection of many complex major discontinuity structures and irregular topographies. Therefore, there is an urgent need to try some new methods to have a deeper understanding of the open pit mine rock slope stability problems.;The intact rock properties and discontinuity properties for both DRC and DP rock formations that exist in the selected open pit mine were determined from lab tests. Special survey equipment was used to perform remote fracture mapping. From remote fracture mapping data, the fracture orientation, spacing and density were calculated. Discontinuity orientation distributions obtained through remote fracture mapping agreed very well with the results of manual fracture mapping conducted by the mining company. GSI rock quality system and Hoek-Brown failure criteria were used to estimate the rock mass properties combining the fracture mapping results with laboratory test results of intact rock samples. Fault properties and the DRC-DP contact properties were estimated based on the laboratory discontinuity test results. A geological model was built in a 3DEC model including all the major faults, DRC-DP contact, and two stages of rock excavation. The built major discontinuity system of 44 faults in 3DEC with their real orientations, locations and three dimensional extensions were validated successfully using the fault geometry data provided by the mining company using seven cross sections. Numerical modeling was conducted to study the effect of boundary conditions, fault system and lateral stress ratio on the stability of the considered rock slope.;Seven monitoring points were selected from the deformation monitoring conducted by the mining company using a robotic total station to compare with numerical predictions. A good agreement was obtained. In overall, the successful simulation of the rock excavation during a certain time period indicated the possibility of using the procedure developed in this dissertation to investigate rock slope stability with respect to expected future rock excavations in mine planning.