1. Sounds: The roof subsides, the mine pressure increases sharply, and the mining face supports deformation, fracture, and bending, accompanied by sounds. Before the old roof is pressed, the roof crack will also emit firecrackers or thunder. 2. Drossing: When the top plate is severely broken, the top plate appears to be slag 3. Piece of help: The pressure on the coal wall is increased, and the coal wall piece is more serious than usual. 4. Crack: mainly refers to the mining fissure caused by the sinking of the roof. The crack expansion shows that the roof is affected by the mining. 5. Separation layer: The method of tapping the top is used. For example, the top plate emits a “beep†sound to indicate that the upper and lower layers have been separated from the layer, which is a sign of the topping. 6. Leaky top: Broken false top or direct top, sometimes leaking tops before large area roofing. 7. The amount of gas emission increases. 8. There is water. Basket Wheel，Basket Cart With Wheels，Basket Trolley With Wheels，Wheel Basket Trolley,Rolling Trolley Suzhou Malltek Supply China Co.,Ltd. , https://www.malltekcart.com
a sign of a common roof accident
a sign of a common roof accident