1, the omens of the film

A. Due to the increased pressure on the roof before the roof is raised, the coal pressure on the working surface and the surrounding roadway is increased, resulting in a change in coal quality and an increase in the number of pieces.

B. Using electric drills at work is more labor-saving than usual.

C. Reduce the working load of the shearer.

2, the omen of the bracket

A, the use of wood a bracket large crushed or broken, and beeps; using metal pillars, ear on the column, an audible sound pressure of the rear pillar.

B. When the pressure of the top plate continues to increase, the living column rapidly shrinks and continuously emits a “giggle” sound; if the working surface leaves a bottom coal or the top plate is soft and broken, the bracket has a bottom insertion and a drilling top phenomenon.

C. When the working surface uses the hinged top beam, there is a “flying wedge” phenomenon under the impact pressure of the top plate, that is, the wedge is extruded or popped.

3, the omission of gas and water

The amount of gas emission in the gas-bearing coal seam suddenly increases; the amount of water drenched from the roof with water is increased.

4, the omen of local topping

A, the sound. The wooden pillars are chopped, followed by the broken beams; the metal pillars are rapidly descending (or down), and they also make a loud noise; sometimes they can also hear the fracture of the roof in the goaf. Stupid thunder.

B, slag. When the roof is severely broken, the broken beam breaks the phenomenon, and then the roof slag phenomenon occurs. The more the slag is, the greater the pressure on the roof.

C, coal wall piece help. The top of the roof is more than usual.

D, cracks. When the top plate crack is widened and deepened, roofing may occur.

E, leaking top. Lax due to back top or the drain is not strong top holder phenomenon appears, if not in time, when the stone continues caving of roof, roof fall occurs no sound signal.

F, the top plate appears to be separated. When the roof is about to fall, the roof separation phenomenon often occurs, and it is necessary to judge by means of knocking and asking the top. That is, the operator stands in a safe place, after using the long steel rod to first break off the broken coal and rock, then hit the top plate with an axe, hoe or steel rod. If the sound is crisp, the top plate is intact; if the top plate makes an "empty" sound , indicating that the upper and lower rock layers have been separated from each other. When the separation layer is very thick, it is not easy to identify. At this time, use the vibration to ask the top method, use the left hand to hold the top plate, and the right hand to use the tool to strike. If the left hand feels a slight vibration, the top plate will be separated from the layer, and the support should be strengthened immediately. .

G. In gas-bearing coal seams, the amount of gas emission suddenly increases.

H. There is a working surface with water spray, and the amount of water spray is obviously increased.

2) Main measures to prevent roof accidents

1. Prevention and control measures for jacking accidents on the working face

A. Prevention and control measures for the push-type roof accident

According to the nature of the top plate, the push-type top-down type is divided into an impact push type top and a composite top push type top.

a, impact push type roof. When the roof of the coal seam is separated from the layer, the basic top rock layer is fractured on the roof rock of the separated coal seam, resulting in a push-type roof.

The main prevention and control measures are: dynamic monitoring of the roof, and the corresponding measures should be taken when the roof is separated. Improve the quality of support, enhance stability and level resistance. The support of the working face should be timely, improve the initial support of the stiffness of the bracket, and prevent the roof of the coal seam from separating.

b. Composite roof push-type roofing. The composite roof consists of rock layers and coal seams of different lithologies. When the lower layer of the composite roof has a small thickness of coal seam or rock formation, insufficient support strength, unqualified bracket quality or large mine pressure, it is easy to cause a composite roof push-type roofing accident.

The composite roof has no obvious signs and features before the roof is launched, and it may occur in any process. Therefore, the quality of the brackets should be strictly checked. The coal mines with conditions should be supported by hydraulic supports and the composite roof. Perform dynamic monitoring.

c, general preventive measures

It is possible to control the mining height so that the soft rock layer falls behind the hard top. Do not destroy the composite roof for mining work. According to the actual work experience, the pseudo-tilt working face is applied. 3 When the masts and trusses are installed, they should be supported in the direction of possible movement of the rock mass.

B. Prevention and control measures for crushing roof accidents

When the basic top of the coal seam is a hard rock, the mine pressure on the working face after the basic top pressure is prominent, especially during the initial pressure and periodic pressure of the working face or the sinking process of the basic top fracture step. If it is unqualified and the strength is not enough, a crushing type roofing accident will occur. The prevention and control measures for the crushing type roof accident are:

a. When the working surface is found to have obvious signs of a big roof, measures must be taken, such as strengthening support and stopping production observation.

b. Conditional mines should establish mine pressure observation and roof dynamic monitoring system to provide basis for working face support.

c. When the upper part of the coal seam is a hard rock layer and it is not easy to fall, it is necessary to use forced topping or high-pressure water injection to the roof to reduce its strength and naturally fall.

d. Increase the working surface control top distance during the initial pressure of the basic top.

f. When the working surface is pressed and the sinking steps appear, the special support form (such as raft and dense bracket) should be used to strengthen the support. Replace the metal pillars in the range with wooden posts, and wait until the sinking range rocks are all in the goaf, and then return to the top of the column.

C. Prevention and control measures for leakage accidents

The skimmer-type roof does not have a clear omen at the time of the big roof. The direct top of the working face is very broken, the dip angle of the coal seam is large, the local leakage roof occurs in the supporting surface of the working face, and the partial direct top is completely leaked, causing the bracket to be unstable and causing a leakage accident. Its control measures are:

a. It is strictly forbidden to blast, move the scraper conveyor and other processes to knock down the bracket, affecting the direct roof and preventing local roofing from appearing directly on the top.

b. After the blasting, the support work must be timely, and the roof must be backed up.

c. The quality of the support must be qualified, and the support has sufficient support.

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