Similar to the F3202 fault, the F19 fault is also connected to the gas discharge. The fault is 36m in the area of ​​the second horizontal wellbore, which tends to NW. The upper two coals are connected to the C3L8 limestone, as shown in Figure 2. The gas in the coal seam is transported to the limestone through the fault, and the gas emission is lower than the surrounding area when the coal mine slope is driven through the coal seam.
1.2 Small faults developed in vertical well fields, some of which are vertical discharge gas. Most of these small-scale open faults are high-angle normal faults (inclination angles above 70°, and fault strikes are close to coal seams).
The 3006 working face in the three-level north wing reveals a high-angle normal fault with a drop of 6m during the mining. The inclination angle is 70°, and the trend is N30°W, which tends to NE, and the entire working surface is cut almost. Through the analysis of the actual data, it is found that the gas emission near the fault is inversely related to the fault drop. As the fault drop increases, the amount of gas emission decreases, and vice versa. The relationship between the two is shown in Table 2.
It is concluded that the gas distribution in the coal seam is affected by the open faults of vertical discharge gas: the gas with the largest fault drop is the smallest, and the gas with the two ends of the fault is the largest. Through the statistics of small-scale open faults in the mine field, most faults reflect this law to varying degrees. 2. Closed fault closed fault refers to the fault that is poor in gas permeability and is not conducive to gas emission. A large number of actual data show that the gas emission is significantly increased near the closed fault.
Located in the F3302 fault of the south wing of the Third Mine, the strike is N35°E, and the fault drop is 20m, which tends to SE. During the mining process, the gas near the fault has an increasing trend. The gas emission quantity of the 3106 working face is used to illustrate this problem. (table 3). The low-angle small faults developed in the minefield are mostly closed. The impact of these small-scale closed faults on the gas distribution is also consistent with the gas near the fault and the law of small gas from the fault. For example, the two-level 2123 working face has several faults around the working face, the difference is 7-9-3 m, and the inclination is 30°~42°. The relative emission of gas in the 2123 working face during the excavation process is closer than that. The area has increased significantly. 3. Analysis of the influence of fault on gas distribution The open fault is due to the large dip angle of the fault, the poor cementation of the fault zone and the good gas permeability, which creates conditions for the gas migration, but the result of the gas migration is release or rich. The set is also determined by the gap of the fault. If the upper 2nd coal seam is connected with the lower C3L8 limestone, and the C3L8 limestone is one of the main aquifers in the area, the karst fissure is relatively developed and the connectivity is good, which provides a good channel for gas emission in the coal seam. In the case of small fault drop, the direct top plate of the No.1 coal in the minefield is sandy mudstone, the gas permeability is poor, and the upper S10 sandstone particles are coarse, the gas permeability is good, and the thickness is large. If the fault completely destroys the coal seam directly The roof, then the gas in the coal seam must be diffused into the sand through the fault and released to the surrounding. However, at the point where the fault is pinched, the relative displacement of the two plates is small, or only some damage is caused to the original structure of the coal seam, and there is no gas release condition in these parts. From the perspective of tectonic stress analysis, under the action of in-situ stress, some of the sorption gas in the coal will be converted into free gas, and the broken coal seam will provide space for the existence of free gas. Therefore, the amount of gas emission at the point where the interruption of the mining process is interrupted is higher than that of the middle part. The reason for the increase of gas caused by the closed fault is the same as the reason for the high amount of gas emission of the open fault at the point of extinction.
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