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(1) The signs and precautions of the big roof
Continue to promote coal mining face forward, stope roof control area will gradually increase, when the small thickness of immediate roof collapse gradually, while hard hanging a large area of exposed roof, slate layer formed on a top face A natural pressure arch, the coal wall is subject to pressure changes, resulting in concentrated pressure on the working face. In this case, if the total supporting force of the working face support to the top plate cannot be adapted to the requirement of maintaining the stable sinking of the top plate, a large roof (or cut top) may occur.
1. The omen of the big top
(1) The omen of the roof:
1 The top plate continuously emits a sound of breaking. This is due to the sound that occurs when the direct top and the old top are separated from the floor or the top plate.
2 The roof rock layer is broken, fallen, and dropped. The drop is generally changed from less to more, from thin to dense.
3 The top plate crack increases or the crack opens, and a large amount of sinking occurs.
(2) The omen of the coal gang. As the pressure increases before the roof rises, the coal wall becomes soft and the coal is softened. When using an electric drill to drill the eye, the eyesight is labor-saving; when the coal is cut with a shearer, the load is reduced.
(3) The omen of the stent. When a wooden stand is used, the stand is largely broken and sounds. When using metal pillars, roof pillars to the pressure caused by rapid sinking living continuously issued a "slightly, slightly" sound, pillars tremble. When the working face uses the spliced ​​top beam, the top beam wedge is ejected or squeezed due to the impact pressure of the top plate, commonly known as the "flying wedge". When the bottom plate is soft or the bottom plate is left with a bottom stone and the bottom coal is lost, the pillars are inserted into the bottom plate in a large amount.
(4) The gas content of the working face is increased or the water is increased. The coal seam containing gas has a sudden increase in gas emission before the roof. There is a roof that is drenched, and the amount of water is increased.
2. Measures to prevent large roof fall
(1) Master the top plate cycle of the working face to control the law. When determining the total supporting force of the working face support, the initial pressure and periodic pressure of the top plate must be considered. If the total support force of the bracket can only adapt to the normal roof pressure, it will pose a serious threat to the working surface when there is a period of pressure. When the total supporting force of the bracket is insufficient to cope with the cycle, the law of the movement of the roof is mastered, the support is strengthened before the pressure is applied, the bracket is increased, and various safety measures are taken to prevent the roof from falling. Therefore, it is necessary to have spare support materials for the mining face.
(2) The coal mining face should have reasonable bracket specifications and support density.
(3) Speed ​​up the advancement of the work surface. Because the progress of the working surface is slow, the amount of roof subsidence is large, so the top plate is incomplete, the wooden bracket is damaged more, and the pressure on the metal pillar is also large. Due to the slow progress and the large number of pillars being damaged, the total supporting force of the working surface is reduced, which makes it easy to push the working surface. Therefore, the speed of the work surface should be accelerated.
(2) Omen of local roofing and preventive measures
The occurrence of local roofing is mainly determined by the rock properties of the roof and the support of the bracket to each roof. When the roof is broken and the joints are developed, the roof will not occur when the support is not carried out. In areas where geological conditions change, roofing is also prone to occur. Sometimes, although the top plate is relatively stable, ignoring the quality of the bracket specifications and violating the operating procedures may cause local roofing.
1. The omen of local topping
(1) The working face encounters a small geological structure;
(2) The cracks in the top plate are opened, the cracks are increased, and an abnormal sound is emitted when knocking the top;
(3) There are live cockroaches in the cracks in the top plate, and there are phenomena of falling and falling, first small and then large;
(4) The contact surface of the coal seam and the top plate, the extremely thin meteorite pieces continuously fall off;
(5) The dripping water dripped from the cleft surface of the top plate.
2. Measures to prevent local roofing
(1) The support method must be compatible with the rock properties of the roof.
(2) The coal mining machine should be pillard in time after mining.
(3) The overall displacement conveyor should take the necessary safety measures.
(4) There must be special brackets on the working face and the lower exit. According to the provisions of the "Safety Regulations for Coal Mines", it is generally adopted to raise the shed in the upper and lower leveling roads, and to lift the sheds at the nose and the tail of the machine. Sometimes it is necessary to add special measures such as dense pillars or rafts to provide special support. .
(5) Prevent the gun from falling into the shed.
(6) Do a good job of returning to the top of the column. It is necessary to put the top of the column back in time, and it is forbidden to use coal when the top distance exceeds the requirements of the operating regulations. After returning to the column, the top plate still does not fall. When the specified ceiling distance is exceeded, manual topping or other effective measures must be taken to force the topping.
(7) Adhere to regular circulation operations.
(8) Adhere to the necessary systems. Such as knocking on the top system, acceptance bracket system, post responsibility system, metal bracket inspection system, handover system, roof analysis system.
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