Stability Analysis Of Slope And Boundary Pillar In Transition Open-pit To Underground Mine

In our country, many metal mines are being mined using open-pit methods. Most of the deep open-pits mines have been turned to underground mines because of the limited resource conditions. Mine shifting from open-pit to underground mining will meet a series of safety problems. Therefore, research on the safety and stability of slope and boundary pillar in open-pit mining is very significant to safety production of these mines. Open-pit to underground mining of Guilaizhuang Gold Mine was selected as the engineering background for in-depth studies in this paper. On the basis of the field survey and measure data, considering the explosive load, strength reduction theory and FLAC3D software are adopted in the analysis of slope and boundary pillar. The main contents of the dissertation are summarized as follows:1. Through scene investigation and rock mechanical test, the distribution of structural plane, rock quality of designation and rock mechanics parameters were obtained. Afterwards, the rock mass quality was assessed based on the data with the methods of engineering geological classification for surrounding rock mass, RMR and Q-system successively. Combined with Hoek-Brown and Mohr-Coulomb criterion, the RMR on the slope rock mass quality evaluation was applied to the evaluation of slope rock mass mechanical parameters.2. Through vibration velocity measurement and research of open-pit and underground tunnel, the decay laws of maximum particles velocity were obtained. Based on the method of dynamic FLAC numeric simulation and the field testing of blasting vibration data, the stability of slope and boundary pillar thickness optimization under the blasting load was analyzed. Then, considering the characteristic in transition open-pit to underground mine, stability analysis of slope and boundary pillar was studied.3. In the ideal detonation theory conditions, the explosive load was imposed on surrounding simultaneous blast deep holes of open-pit with equivalent stress of triangular wave. The stability and plastic zone of stope with different span and boundary pillar under the blasting load was analyzed. The fitting relationship of additional stress, vibration velocity and the thickness of the key points of boundary pillar were obtained. Then, considering the static and dynamic loading respectively, the method of strength reduction was introduced into stability analysis of boundary pillar. Based on the convergence law of displacement time history curve at specific measuring point, a new criterion was put forward. Combined with displacement vector characteristics, the stability of boundary pillar was quantitative evaluated with the method of strength reduction.4. The theory of load-unload response ratio (LURR) was introduced to analyze dynamic slope stability and boundary pillar safety thickness, In the limited state of slope and boundary pillar undel blasting load, the LURR regulation of stable and unstable characteristic point was studied. A strength reduction failure criterion was supplemented.