Application Of Finite Element Strength Reduction Method In Vertical Shaft Uncovering Outburst Coal Seam Analysis

Coal and gas outburst is a powerful geological disaster in the process of coal mine production. It is also a dynamic phenomenon accompanied by strong sound and severe mechanical shock. With its Expansion from the shallow to the deep, the intensity of mining also increases and the risk of uncovering Shaft where coal and gas outburst has a potential to occur also increases, which brings pressure to the safety and efficiency of coal production.In recent years, with the development of computer technology and finite element analysis software, the finite element strength reduction method has been accepted by most scholars and engineers, being rapidly applied and developed in the field of geotechnical engineering. Finite element strength reduction method greatly expands the applicability of the limit analysis method, which can analyze complex landform and geological slope without being restricted by geometric shape of the slope and boundary conditions. Unlike traditional limit analysis method, finite element strength reduction method can automatically generate failure surface, while the former assumes a failure surface in advance. In this paper, finite element strength reduction method is used in the numerical simulation of vertical shaft uncovering coal seam, analysis of rock mass stress distribution and positions of plastic zone of coal seam. Then, its result guides the design of exploration drilling and gas drainage drilling. And it is also of a very great theoretical and practical significance to coal and gas outburst prevention and treatment.Taking the wind air shaft tunneling face in the deep in Huainan Pansan mine as the research object, with finite element strength reduction method and a combination of collected data, theoretical analysis and numerical simulation, the vertical stress distribution of coal and rock around tunneling face and the plastic zone of coal seam is studied and analyzed.The numerical simulation results show that stress distribution of coal and rock around the vertical shaft tunneling face are similar under the conditions of different shaft diameters, different thicknesses of rock pillars and different gas pressure, where high pressure area, relief area and the original rock stress area all exist.According to the stress distribution of coal and rock around the vertical shaft tunneling face, the drainage work are conducted for 49 days by using fan-shaped continuous intensive gas drainage drilling. The cumulative amount of drained gas is 53991m3 and coal seam gas pre-pumping rate reached 50.8%, the maximal pressure of residual gas in the region of coal 5-2 group evaluation is 0.05MPa, the maximal residual gas content reached 2.6m3/t. It effectively reduced the gas pressure and gas content of coal seam. The outburst prevention effect is obvious.Research could well guide drilling layout, measurement of gas pressure and content in the mine. It has significant effect to the prevention of coal and gas outburst, effectively ensuring the safety of mine production.