Research On Goaf Stability Of Open Pit Mines Based On Catastrophe Theory

Open-pit mining has won great popularity in China as it has high production efficiency and simple production technology. However, many open pit mines had been underground mined for a long time, with numerous goafs without being filled, which has being posed severe threat to the safe production, mining operators and equipment. Therefore, to carry out research on the goaf stability is particularly important and urgent. According to the complex goaf conditions in Sandaozhuang open pit, the stability classification and the safety factor were examined by incorporating these research methodologies of multi-level fuzzy comprehensive evaluation method, strength reduction and catastrophe theory etc. The research contents and results are detailed as follows:(1) Judging by the field-survey-based parameters, reasonable influencing factors and the impact elements were selected to assess the stability of28goafs in the mining area by2-level fuzzy comprehensive evaluation. The evaluation took the open pit mining influence factors into account for the first time and the stability degree of each goaf was determined. The results agreed well with engineering practice.(2) Three dimensional numerical simulation was used to investigate the single regular and overlapping regular goafs with varying span and roof thickness. Based on the displacement of the key points, the safety factors were calculated and discussed from the perspectives of shear failure and tensile failure, by coupling strength reduction and catastrophe theory. The results show that the goaf failed by shear more obviously, indicating that the shear safety factor should be assumed as the overall safety factor of the goaf. In addition, The law of safety factor influenced by both span and roof thickness was obtained respectively. Furthurmore, the numerical results coming from the overlapping goaf simulation verified that different deformation behaviors happened in the roof of the goafs. (3) Strength reduction and catastrophe theory coupled analysis were applied to investigate a typical complex goaf in Sandaozhuang open pit, A credible safety factor was obtained, which provided a strong basis for safety management of the next goaf.