What Are the Different Types of Exterior Cladding?

Overburden rock, a rock formation that occurs above a coal seam, is also called a roof. The layer of rock that exists under the coal seam is called the floor. Before the roadway is excavated, the underground rock or coal seam is solid, and the weight of the upper rock layer is pressed on the lower rock layer and is in a balanced state. At this time, the rock mass does not deform and does not move. After we dig a roadway in a coal seam or rock formation, the rock formation at the top of the roadway will fall ^[1] .

Generally, it is divided into false roof, direct roof and old roof according to whether the overlying rock layer (roof) is easy to fall and the distance from the coal seam.

False roof: directly attached to the coal seam, the thickness is below 0.3-0.5 meters.

(1) Formation of the "Three Belts"

After the coal seam of the longwall working face is mined, part of the roof on the coal seam must be collapsed to fill the goaf. This part of the rock layer is generally called the collapse zone rock layer (equivalent to direct roofing); The settlement of the rock layer and the height of the free space are getting smaller and smaller until the collapsed geometric conditions are not met. At this moment, the lower fractured rock layer zone will form a balanced structure. This part of the rock formation is equivalent to the old top, and some schools call the fractured rock formation zone the fissure zone (It is worth noting that the fractured zone includes the old top, but not necessarily all of it.) The rift zone is slowly subsiding to the ground ^[2]

The existence of the primary structural surface in the rock mass and the damage surface caused by rock engineering construction divide the rock layer into many blocks. The law of force transmission in a block is different from continuous media. The study of the stress distribution law in the block has led to the development of rock block mechanics theory. The research on the contact block structure of the overlying strata above the stope will undoubtedly enrich the research content of block mechanics theory. ·

All in all, studying the block structure formed by overlying strata on the stope in the form of surface contact can be used to guide the related problems of rock formation control in mining engineering, which has important engineering practical significance, and can also enrich and develop mine pressure and rock formation control theory Has important theoretical value ^[3] .