Discussion on the prevention and control of coal a

Discussion on the prevention and control of coal and gas outburst in heading face

coal and gas outburst accident is a complex dynamic phenomenon that requires considering the maximum stress of the tested material. So far, although there are many hypotheses, none of them has fully mastered the laws of coal and gas outburst under various geological and mining conditions

the dangerous area of coal and gas outburst is actually equivalent to having predicted the outburst risk. The next priority is to take outburst prevention measures. Therefore, when formulating and implementing coal and gas outburst prevention and control measures in the process of tunneling, we should adjust measures to local conditions, combined with the actual situation of the coal seam currently being excavated in the mine, collect past basic data and formulate feasible outburst prevention measures according to the detailed rules for the prevention and control of coal and gas outburst, so as to ensure the safe production of the coal mine underground

the measures to prevent coal and gas outburst are divided into regional coal and gas outburst measures and local coal and gas outburst measures. Regional outburst prevention measures generally include mining protective layer, pre drainage of coal seam gas and coal seam water injection. Among many regional outburst prevention measures, mining protective layer is one of the most effective outburst prevention measures

take xiaoyunpan coal mine in Xichong Town, Panxian County as an example. After the coal mine is mined to +1500 meters deep, due to the structural influence of f63 reverse fault on the north wing and zhujiafen anticline on the south wing, it is revealed that 3 #, 7 #, 9 # are outburst coal seams, and the outburst risk is relatively large. It is also a steep coal seam with an inclination of 550 ~ 750, so the mining of protective layer is not suitable for this mine. In addition to mining the protective layer, the more effective regional measure is pre pumping the gas from the 3# coal seam. The essence of this measure is: by drilling a large number of dense boreholes into the 3# coal seam, local pressure relief is caused, and gas is discharged and gas pressure is released at the same time; After 6 months of pre drainage of 3# coal seam gas, the tile pressure and gas content in the coal seam are further reduced, resulting in the shrinkage and deformation of the coal seam, increasing the firmness coefficient of the coal and reducing the in-situ stress. The main reasons for coal and gas outburst are in-situ stress and the physical and mechanical properties of coal. Pre drainage of coal seam gas can reduce in-situ stress, enhance the physical and mechanical properties of coal, and reduce gas pressure and gas content. It can be seen that the pre drainage of coal seam gas can be used as a prevention and control measure for coal and gas outburst in xiaoyunpan coal mine, Xichong Town, Pan county

after the regional outburst prevention measures are taken, the outburst risk of the mining face must be predicted. If it is a mining face with outburst risk, the outburst prevention measures of the mining face must be taken

the places where coal and gas outbursts occur in xiaoyunpan coal mine in Xichong Town, Panxian county are basically the supporting parts of the hydraulic universal testing machine. When driving at the heading, uphill and drift, not only the in-situ stress of the heading and the physical and mechanical properties of the coal body, but also the self gravity stress of the coal body should be considered. Therefore, measures combining advance drilling and advance metal framework should be taken

drilling ahead can make the concentrated stress and high gas pressure near the working face move far to the front of the working face, so as to reduce the stress and gas pressure gradient near the working face and form an 8-10 meter long pressure relief zone and gas drainage zone in front of the working face; The use of advanced metal framework can prevent roof fall and induced outburst due to the soft top coal of the heading face. A row of advanced metal framework is first installed along the top of the roadway in front of the heading work, which can support the coal on the top of the roadway and discharge gas. Its main purpose is to enhance the stability of the coal above the roadway

after the advance metal framework is erected, the next work is to use qbz-22 portable outburst prevention drill to drill advance holes. The advance drilling is to drill three rows of 18 holes in the front of the coal body in the excavation face, each of which is 10 meters deep, and always maintain a 5-meter advance distance, so that the coal body in front of the excavation can relieve pressure and discharge gas, so as to achieve the purpose of weakening or preventing coal and gas outburst

xiaoyunpan coal mine in Xichong Town, Pan County +1500 meter crosscut coal uncovering measures, because the mine is a steeply inclined coal seam. Through the comprehensive evaluation of the outburst phenomenon that occurred during the coal uncovering of each crosscut in the past, the crosscut adopts the pre drainage of coal seam gas as the outburst prevention measures for the coal uncovering of the crosscut, and the measures are as follows: 1. During the excavation of the crosscut excavation face, the measures of first exploration and then excavation are adopted for excavation. When the head-on floor of the working face is 10 meters away from the normal distance of the coal seam roof, two front exploration holes penetrating the full thickness of the coal seam and entering the coal seam roof not less than 0.5 meters are constructed at the head-on of the roadway, Verify the occurrence conditions, geological structure and gas conditions of the coal seam in front. 2. When the normal distance between the top (or bottom) plate of the heading face of the crosscut heading face and the coal seam roof is 5 meters, two front probe holes penetrating the full thickness of the coal seam in the middle and entering the coal seam roof at least 0.5 meters are constructed in the heading face to further explore the occurrence of the coal seam in front, and three prediction holes are constructed in the working face to predict the outburst risk of the coal body in front. If there is a danger of outburst in the working face, the gas pre drainage must be carried out on the coal body in front of the working face construction drainage borehole. The drainage borehole is arranged in the coal seam of 5m from the contour line of the crosscut, and the diameter of the drainage borehole is 75? 50. The hole spacing and row spacing are 0.3m, and the hole bottom spacing is 2m. 7 pumping holes are drilled in each row, with a total of 5 rows. After the construction of each drainage hole is completed, the hole shall be sealed in time for drainage, and the drainage gas of the drainage hole shall be tested to ensure that the gas concentration of all drainage holes in a single hole is reduced to less than 10%, the gas content within the control range of the drainage hole is less than 8m3/t, and the gas pressure is reduced to 0.74mpa. After there is no danger of outburst, the tunneling can be carried out forward. When the tunneling is 3 meters from the normal distance of the roadway to the coal seam, the long-distance blasting shall be used to uncover the coal, Until the coal seam is uncovered

after the measures are taken, the effect of the measures should be tested. If the measures are invalid, additional measures should be taken. The additional measures for coal excavation include deep hole loosening blasting, and the additional measures for coal uncovering by crosscut include discharge drilling, etc; If the measures are effective, the tunneling operation can be carried out after taking certain safety protection measures

compared with local coal and gas outburst measures, the advantage of regional coal and gas outburst measures is that they are taken in advance before the mining work is carried out. The construction of measures and mining operations do not interfere with each other, and the effect is good. Therefore, regional outburst prevention measures should be given priority. However, in the process of coal mine excavation, no matter what kind of outburst prevention measures are used when heating, this measure is an effective outburst prevention measure as long as the mine excavation engineering can be completed safely and efficiently