Coal mine fields within Chensilou coal layer 4 layer 2 are two, three one, two three, four three layers. In the early stage of the mine, the second coal seam was mined. The minimum thickness of the coal seam is 0.5m, the maximum thickness is 3.85m, and the average thickness is 2.45m. The coal seam structure is simple and the coal seam inclination angle is 0~13°. The fully mechanized mining face is inclined long wall strip type inclined mining with a face length of 190m and a strike length of about 1000m. The old roof of the coal seam is a fine sandstone with a thickness of 10m; the top of the old roof has a composite top of interbedded layers of sandy mudstone and mudstone. The thickness is unstable, 0~3.0m, and local fissures develop, especially in the geological structure and the roof near the oblique axis. Broken, bringing great difficulties to safe production.

1 piece to help the top

At present, there are two fully mechanized mining faces, namely 2101, 2103 working faces. From the mining situation of the two faces, the top plate of the working face is relatively broken, especially the composite roof thickness of the coal seam is unevenly changed, and the joints are developed. In some sections during the mining process, the thickness is relatively thin (0.3m or less). After the thickness is gradually increased, the maximum mining height of the working surface according to the height of the bracket can reach 3.2m, and the average thickness of the coal seam is 2.45m, generally 2.0 to 2.7m. When the direct top is 0.5~1.0m, if it can't be retained when coal mining, in addition to affecting the coal quality, the height of the bracket can still meet the support needs; if the thickness exceeds 1.0m, it can still not be retained, let it fall, The bracket can not be connected to the top, thus endangering the safety of the work surface. For example, if the working face of 2103 is pushed to 180m, the 100~126 frame of the working face will have a roofing accident, accounting for 20% of the total length of the working face, the most serious of which is 117-126, 15m long, and the composite top above the coal seam. The thickness of about 2m is all falling, the composite top thickness of other sections is 1.0~1.5m, and the working surface height is 3.0~4.0m. The falling meteorites are all pressed on the conveyor, causing the conveyor to be crushed to death; and if the 2101 working face of the second team is pushed to 280m, the working face has a serious gangming phenomenon, and the length of the gang section is the length of the working face. 52%, the top-down section caused by the film gang accounted for 15% of the working face length, the processing time was up to half a month, and the monthly output fell to 20,000 tons, which is about 1/3 to 1/4 of the normal. The material consumption is 4 to 5 times the normal period.

2 pieces of help-seeking cause

The top of the working face is mainly caused by the long overhead time caused by the gang, and the top plate is separated from the layer and causes the roof to fall. The working face is more pronounced during the period of pressure. There are roughly the following reasons:

(1) During the working face, the coal seam is pressed and the composite roof automatically falls.

(2) If the frame is not moved in time or the frame is not in place, the distance between the top and the top is large, and the time of the top is long.

(3) Over the geological structure, the roof is broken, and the coal miner does not have a good angle when cutting coal.

(4) The method of falling coal is unreasonable, and the coal mining machine falls into coal, which often causes the roof to be untimely or the roof to be damaged, resulting in roof collapse.

3 pieces of measures to help the roof

3.1 Change the coal mining process

(1) The height control is between 2 and 2.5 m, and the maximum is not more than 2.5 m, ensuring the effective support force of the bracket and the reduction of the coal wall pressure.

(2) The method of breaking coal rock is changed from mechanical coal cutting to wind-slipping coal or small gun vibration to break coal rock, shallow depth, one stone per coal cut once. When shooting, the blasthole is arranged as: 1 row of bottom eyes, 1000mm from the bottom plate, and the dosage of each eye is about 150g.

(3) Roof support: The top plate exposed after the shot is manually advanced and the column is used to protect the column and the shed. The beam is made of logs with a diameter of 180-200mm. Coal gang, the other end is inserted into the top beam of the bracket, 1 shed on the 1 shed, then the slab beam and Jingjing are arranged on the lower shed beam, and the 1 knive 1 back top method is used to ensure the effective control of the roof. Under normal circumstances, the advance axillary depth is not more than 3m from the cable trough forward, so that the shearer can cut coal at the top of the two top plates through the working face.

(4) Coal cutting measures: The coal mining machine cuts here, if the fault location is close to the machine head, the front and rear drums are raised at the same time (because the coal rock is also broken by artificial), it is in the no-load state, and the rear roller is allowed. Stop, the front drum idling, after the passage, then start the drum, but at this time the section does not push, after the machine head is cut through, exit the shearer, and the top plate is in good condition after the fault. When the shearer passes here, the front drum is still raised and stopped, and the rear drum is lowered to cut the bottom coal and coal. After the drum is over, the roller is immediately pushed and quickly pulled, and the bracket top beam is supported by the lifting shed.

3.2 Method of using shallow feed

The moving frame adopts the topping shifting frame, and the frame is moved in time to reduce the exposure time of the top plate to prevent the occurrence of artificial roofing accidents.

3.3 Using the blasting method to stay top

In the process of propulsion in the fully mechanized mining face, the composite section of the local section becomes thicker, and the normal coal seam begins to descend, and it is very difficult to recover the coal. For example, 2101 working face 15~25 total 15m, composite top thickness more than 1.5m, coal thickness 2m, mining up to 3.5m high, is not conducive to safe production, coal quality is not good. Take the top board from the two sides to the middle to advance the way. Specific method: the composite top opening is perpendicular to the coal surface from both sides of the composite top section, the specification is 2m×2m, and the single pillar is supported by round wood; the two sides are driven to the middle until the excavation; the coal mining machine passes here. Cut coal, only clean up the floating coal; when moving the frame, first drop the frame and then move the frame.

4 pieces of preventive measures to help the roof

4.1 Reinforce the coal wall by bolting the coal wall to reduce the top of the working face of the gangster. In order to reduce the work surface, the work surface should be reinforced. Reinforcement method: use ordinary wood anchors to hit the coal wall. Specific practices: (1) inverted wedge wood anchors, length not less than 1.5m, diameter 38mm, wood pallet specifications 200mm × 200mm × 25mm. (2) Two rows of anchors are placed on the coal wall with a row spacing of 700 mm × 700 mm, 3 eye arrangements, and the anchor eye diameter is 42 mm. (3) The front end of the three brackets at the front and rear of the anchoring rod are backed by the top, and the bracket is effectively connected to the top, and the initial supporting force is achieved. The order of construction is: knocking on the top of the temporary tripod and anchoring the anchor eye to set the anchor and the upper pallet.

4.2 Advance shifting, fast moving, reducing beam end distance

According to the characteristics of the hydraulic support without the telescopic beam and the side guard plate, in the sheet section, the method of pushing the frame first and then pushing the slip is adopted to reduce the distance between the beam end and the coal wall to prevent roofing.

If the coal wall piece is more serious, it can be pre-supported, that is, when the coal wall just happens to be cut, the coal is not required to be cut by the shearer, and the bracket uses the margin between the front column and the conveyor to move forward, so that the coal The roof of the wall panel is supported in advance. At this time, the mining process is a transfer-mining-pushing conveyor, which can greatly reduce the empty top distance and the empty top time of the beam end and the coal wall. After the coal cutter cuts the coal, the bracket is moved in time and the conveyor is moved. At this time, the mining process is a coal cutting-shifting-pushing conveyor. To this end, a depth of cut is required between the front pillar of the bracket and the cable tray bracket of the conveyor. This method is used for the coal seam with broken roof and easy to fall. Under the premise that the advance transfer frame is still not effective, a round log is placed on the front beam of the bracket to support the top plate.

5 Conclusion

As a result of the above measures, the roof management situation has been improved, and the roof has been effectively contained, providing a relatively successful experience for the fully mechanized mining face to achieve safe production under the condition of broken roof. However, these measures are still not perfect and need to be improved. It is necessary to study the roof control method that is more convenient and convenient for the site, such as roof curing technology, to ensure the stable production and high yield of the fully mechanized mining face.

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