The Analysis Of Rock Burst Risk And Prediction Of Hazardous Areas During The Deep Mining For Lingnan Gold Mine

Violent dynamic hazards such as rock bursts frequently happen during deep excavation of mineral mines, due to the high stress and strong disturbance in the deep underground environment, which has greatly limited the further exploration of deep excavation. The thesis, based on a research programme under the National High Tech Research and Development Scheme (Scheme863) named Monitoring and Analyzing Rock Bursts in Deep Mining, uses Lingnan Gold Mine’s historic rock bursts as a case study target.1. By looking into the rock mass structure, we understand the geological structure and the hydro-geological conditions of the deeper Lingnan Gold Mine. As we apply Stress Relieving Method to measure the in-situ stress of six spots from three middle sections of Lingnan, and use Partial Least Squares Method to conduct inversion on the Initial Earth Stress of Lingnan, we find the regularity of in-situ stress distribution, and are able to come to a conclusion that Lingnan is located at a Stress-Concentrating Zone, which enjoys higher rock bursts proneness, based on the Stress Concentration Factor, according to the Geodynamic Division Theory.2. Modeling the stress development process that happens to Lingnan during excavation via numerical simulation, the Arch Effect is found evident in the excavated structure. Stresses abnormalities have been found concentrated in the transverse drift of tunnel face, and transverses at the same level of the tunnel face together form a Stress-Concentrating Slip, which, together with the tip of the Stress Arch, manipulates the Stress fluctuation of the whole excavated region. Using the Coulomb Stress Perturbation Model and dynamic features to analyze the collected responses from fault towards perturbation created during the excavation, we found the distribution of Stress Strengthening and Weakening Area. Based on the above discoveries, we provide a rock burst prevention solution, which is to re-adjust the sequence of excavation, without affecting the overall mining structure, so as to significantly lower the maximum principal stress and ultimately reduced the probability of rock burst.3. After several rounds of uniaxial resist compression tests and tensile tests on rocks in Lingnan, and a study on the dynamics features, we found that the Non-alterating Surrounding Rock Zone enjoys higher rock burst proneness, and consumes larger elastic energy before destruction, which leads to a much more vibrant rock burst. Cyclic triaxial loading tests are also carried out to conduct co-relation analysis between the Elastic Energy Index of rocks with outburst proneness and their damage variable. The results have shown a positive co-relation, and also help define the danger range of indexes based on the necessary conditions for a Deep Surrounding Rock Burst. Acoustic Emission (AE) Experiments are completed to obtain the AE response data from rocks with outburst proneness when loaded destruction. It has been found that the Energy Accumulated Counts of Middle-Level Rocks in terms of out-burst proneness are ten times larger than Lower-Level Rocks. The distinguished data difference has given a new approach for an instant on-site judgment of the outburst-proneness of rocks.4. The thesis brings up two new concepts on rock bursts under deep excavation circumstances, Probability Index and Vibrancy Index, to define the likeliness of a rock burst and its extent of destructive consequences. A multilevel probability computation matrix for Lingnan is established, taking geological conditions, depth, litho-logical composition, stress, power occurrence, etc. into full consideration, so as to identify hazardous regions with higher risks for intensive rock bursts. A preliminary result computed purely based on the matrix has shown to be close to the actual report of historic microseisms collected by micro-seismic monitoring. Based on the result, we conduct a research on a pool of20middle sections of Lingnan (located at-607m), where further excavation will quickly commence, and identify hazardous regions. The above results will be integrated into the "Lingnan Mine Rock Bursts Probability Analysis System", an effective and efficient tool to predict and prevent hazards, which could be seen as a potential contribution to higher security in the practice of deep excavation.