Gas emission coal mining other natural factors coal gas content, geological structure, adjacent layers by gas occurrence status, but also affected by the intensity of mining, mining technology and other factors. During the advancement of the working face, the amount of gas emission often fluctuates. However, in the early stage of mining, especially before the first pressure from the old top, the gas emission from the working surface was relatively small and relatively uniform. The reason:

(1) The length of the goaf is small, and the total amount of coal lost on the working face is small.

(2) The old roof has not yet landed, and the range of the fracture zone is small. There is no channel for the flow of gas from the adjacent layer to the goaf.

The source of gas in the initial working face is relatively simple, mainly the mining layer itself, which is a favorable aspect of gas control work; on the other hand, the goaf is shorter, the roof is less damaged, and it is affected by mining in the vertical direction. The range is not large, so some common gob area drainage methods such as goaf, top plate drilling, traditional roof high pumping, etc. do not work or the effect is not good.

In the high gas coal mining face, Panyi Mine adopted a new gas drainage technology such as high-drilling roadway and low-level high-drainage roadway, which solved the problem of gas during the initial mining of the working face and has become the initial mining face of coal mining face. The main means of managing gas during the period.

2 Gas drainage technology for high-drainage roadway during the initial mining of working face

That is to say, the high-drainage roadway is arranged on the roof of the coal seam, the roadway horizon is strictly controlled and the inclination angle is adjusted, and the large-diameter borehole is drilled in the high-drainage roadway, and the two are communicated artificially, and the high-drainage roadway is used for the first time. The gob area gas can be drained before.

Take the 2622(3) working surface as an example. The coal seam is 13-1, the working face is 960m long, the inclined length is 180m, the elevation is -540～-570m, the coal seam inclination is 4°～9°, the layer thickness is 4.38～5.0m, and the gas content is 6～12 m3/t. The absolute gas emission from the working face is 20~30 m3/min, and the fully mechanized top coal is 3m high and the coal is 2m high.

(1) Selection of high drainage lane level. In the return airway, the construction roadway will be built 25.3m along the inclined direction of the working face, and then it will be climbed 5° in parallel with the return airway, 20m away from the 13-1 coal seam, and the horizontal construction will be maintained at the vertical distance. In order to make the high pumping lane play a role during the initial mining of the working face, it will start to change direction when the remaining length of the design is 60m, and reduce the horizon, and the vertical distance will be reduced to 10m, that is, the front section 60m is arranged in the falling zone. The section of the high-extraction roadway is 2.4m×2m, and the horizontal distance from the return airway is 19~20m.

(2) Construction of the top plate through the hole. Before the mining of the 2622(3) working face, the first face of the high-drainage roadway will be drilled through the 2m high-drainage roadway with the opening of the working face, and the hole is drilled through the high-drainage roadway. The hole diameter is 108mm, the number of holes is 20, and the drilling arrangement is shown in Figure 1.

(3) Analysis of pumping effects. Two Φ273mm welded pipes are installed in the high-drainage roadway of 2622(3), the pipeline is connected to the high-drainage roadway to the inside of 100m, and the raft is protected by 5m around the pumping port. After the pipeline is connected, two closed walls are built at the outer exit of the high pumping lane, and the two walls are cemented with cement. The pumping pipe is connected with the ground drainage system, and the high-drainage roadway is used to drill the gas during the initial mining of the working face.

2622 (3) The working face begins to pick up on the 3rd day, and the pumping concentration is 15% to 20% at 40m (before the old top is not falling), and the pumping flow rate is 6~9 m3/min. The rate is 40%, and the gas concentration of the working face returning air is 0.5%-0.6%. When the working surface advances more than 40m in the high pumping lane (that is, the old top is behind), the pumping capacity of the high pumping lane is obviously increased, and the pumping concentration is 30. %～50%, the pumping flow rate is 12～16 m3/min, the pumping rate is above 50%, and the gas concentration of the working face return airflow is 0.5%~0.7%, which effectively solves the initial mining and normal mining period of the working face. Gas problem. The curve of the pumping amount of high pumping with the propulsion distance is shown in Fig. 2.

(4) Precautions. First, the level of the high-drainage roadway should be in the crack zone of the goaf; second, the horizontal distance of the high-drainage roadway should be controlled within the range of 15~20m, and the roadway leakage will occur when the distance is too close; Too far away, the end of the drainage roadway is not in the gas-rich area, and the drainage effect is not good.

3 Gas drainage technology for low-level high-drainage roadway in the initial stage of mining face mining

The low-level high-drainage roadway is a short roadway specially designed to solve the gas problem in the early stage of coal mining work. Compared with the high pumping lane, the length is short, the horizon is low, and the service time is also short.

Take the 2351(1) working surface as an example. The working face is 997m long, the slope width is 185m, the coal seam inclination is 8°～10°, the coal seam thickness is 1.64～2m, the natural gas content of the coal seam is 6～7 m3/t, and the absolute gas emission of the working face is 15～16 m3/min. The high-grade general mining method is adopted, and the mining height is 1.9m.

3.1 Level control of low level high pumping lane

In the 2351(1) working face, the 17° uphill construction is 13m, and the distance from the coal seam roof is 5m. The vertical distance from the return air lane is 5m, that is, it is arranged in the falling belt, and the horizontal distance is 10m. Bolt support is adopted, and the section size is 2m×2m. The arrangement is shown in Figure 3.

3.2 Construction of the top plate through hole drilling

After the construction of the low-level high-drainage roadway is in place, the top surface of the high-drainage roadway is drilled through the working face and the drilling is required to drill through the low-level high-drainage roadway. The hole diameter is 108 mm and the number of holes is 20. Then, a closed wall is built in the outer part of the low-level high-drainage roadway, and two Ñ„219mm gas pipes are taken out from the closed wall, and connected with the drainage system, and the low-level high-drainage roadway is used to draw the working face during the initial mining period. Gas. Its penetrating borehole is roughly the same as before.

3.3 Analysis of pumping effect

At the beginning of the second mining, the pumping starts, and when the temperature is 40 m3/min (before the old top is not falling), the pumping flow rate is about 3~4m3/min, the maximum is more than 5 m3/min, and the pumping rate is 40%. Successfully solved the gas problem during the initial mining of the working face. The curve of the pumping amount with the propulsion distance is shown in Fig. 4.

4 Working face tail pumping gas drainage technology

The tailing lane can also achieve good drainage effect during the initial mining. Take the 2351(1) working surface as an example. The coal surface of the working face is 9°, the natural gas content of the coal seam with a thickness of 1.9m is 6～7 m3/t, and the absolute gas emission of the working surface is 16～18 m3/min. The comprehensive mechanized coal mining method is adopted. m.

Open the cutting direction along the working face and the coal seam roof construction up 7m, then change to the parallel direction of the upper wind tunnel to the coal seam roof construction 50m flat road, and then change to the upper wind tunnel, the section is 2.4m × 2m. The length of the tail pumping roadway is 50m, and it is 6m out of the return airway. Before the working face is recovered, two closed walls are built in the outer mouth of the tail pumping road, and then two Φ219mm gas pipes are taken out from the closed wall. The ground drainage system is connected, and the layout of the tail pumping lane is shown in Fig. 5.

The working face began to pick up the 2d tail pumping lane and began to pump. At the initial stage of the mining face 50m (before the old top is not falling), the pumping flow rate has been maintained at 4~6 m3/min, and the pumping rate is over 50%, which ensures the safe production of the working face.

5 Economic Benefit Analysis

(1) Solved the problem of gas overrun during the initial mining of high gas coal mining face. The working face can be gas-drained during the initial mining period, which changes the flow field distribution of the high-concentration gas upward turbulent flow, and the gas concentration and the return gas concentration at the upper corner are greatly reduced, which solves the initial mining period. The problem of over-limitation of the angle of the horn and the return gas is greatly reduced due to the over-limit power failure of the gas, which reduces the frequency of mechanical accidents and reduces the frequency of mechanical accidents.

(2) Achieving high productivity and high efficiency of the working face. The monthly output of the high-grade general mining face during the initial mining period was increased from 20,000 to 30,000 tons to 30,000 to 40,000 tons. The monthly output of the fully mechanized mining face during the initial mining period was increased from 4 to 50,000 tons to 6 ~80,000 tons, to ensure the high productivity and efficiency of the work surface.

(3) The sections of special roadways such as high pumping lanes and tail pumping lanes are not, the construction progress is fast, the management is simple and safe, the technology is economical and reasonable, and the drainage effect is also better than that of the upper corner buried pipe and the top plate drilling, so it becomes Panyi Mine currently solves the main method of gas problem during the initial mining and normal mining of high gas coal mining face.

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