Slope Stability Analysis In The Process Of Transition From Open-pit Mining To Underground Mining

Slope stability is considered to be one of the key problems of the process of transition from open-pit mining to underground mining. Recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms process involed and the associated risk. The kinematic behavior of slope stability, deformation and failure, which are concluded in the analysis of slope stability, is simulated using a2D discrete element model (PFC2D code). PFC’s capability of providing full insight into the internal mechanism and thorough process of rock mass destabilization is a particular advantage over conventional FEM which, as conventionally used, only indicates final results with no interim results during the failure process. The modeling methods and procedures presented here demonstrate an approach to the simulation of a rock mass and the stability of excavations in a rock mass.With this approach, study of the stability of excavations can be carried out in such a way that the development and movement of the rock mass and failure suface can be visualized. With the understanding of where the failure will start, how it develops and where the failure will start, how it develops and what the final failure looks like, a more relevant strategy-such as reinforcing the rock to stop the failure at ite inception or exploding the rock to enforce artificial caving-can be sdudied and appropriate measures can be taken.Centered on the investigation, the following work is carried out:1. All numerical simulations by PFC require proper selection of microparameters by means of calibration in which the response of the numerical modeling as compared to the observed results of the physical material. The physical information of the real intact rocks and discontinuities in detail through measuring a large number of discontinuities on the surface of the rock are captured by Point Load Test and advanced ShapeMetrix3D digital photogrammetry measuring system, respectively. The rock mass mechanical macroproperties, such as the compressive strength (UCS), tensile strength, Young’s modulus, cohesion and internal friction angle, are then derived by rock mass quality classification and modified generalized Hoek-Brown strength criterion.2. The most efficient approach involes a trial-and-error process, because no complete theory can reliably predict macroscopic behavior from microscopic properties and geometry. Thus a series of biaxial numerical tests and Brazilian tests on granular samples are performed to derive the rock mass mechanical macroproperties of the granular assembly. The match of deformability in the biaxial and Brazilian tests maximizes the similarity of the numerical representation to the real rock mass.3. The simulation of the western rock slope of Heishan metal mine is carried out with the microparameters. Cross-section of the model is chosen where Y=123250based on the geological coordinate system. Strength reduction method is introduced into the particle flow code for experimental study of slope stability safety factor.4. In the case open pit mine changes into underground mine, the slope-coupling ore body must be recovered on time, which would disturb the stability of the rock mass. Studies have been made on the behavior of slope deforemation and the formation of overburden cover is also studied.