Block roof support
BLOCK ROOF SUPPORT (EN: blocking support, block timbering; DE: Blockausbau; FR: soutenement de blocs; ES: entibacion por bloques; RU: блочная крепь) is the continuous multi-hinged mining roof support, which is made of the concrete blocks; they use it within the horizontal mine workings with the rock pressure of 294-392 kilopascals or more.
Within the USSR, it has been used for the first time during the heading by the tunneling shield of the water-bearing rocks under the Neglinnaya river during the construction of the 1st phase of the Moscow Metropolitan subway (during the start of the 1930-ies). They construct the block roof support of the prefabricated concrete blocks with the mass of 100-130 kilograms (which are sometimes reinforced with the metallic framework), with the thickness of 300-400 millimetres. It is able immediately after installation to bear the pressure of the rocks, which permits to erect it near the stope of the mine working without the usage of the temporary roof support. They distinguish the block roof supports with the reverse vault (see the Figure # 1, a) and without the reverse vault (see the Figure # 1, b) for the rigid or flexible modes of service.
The flexibility is achieved using the installation of the shims, which are made of wood or synthetic materials (on the base of polystyrene, or others) with the thickness of 10-40 millimetres, which are crumpling under the load, between the blocks. For the erection of the block roof support, they use the template-layer for the roof support with the vault, which is corresponding to the cross section of the mine working, and the winch (see the Figure # 2).
Simultaneously with the laying of the blocks, they fill the fixated space with the rock. They install the keystone block last. They embed the wooden shims near the keystone block from the end. There are consumed from 24 to 46 blocks with the total volume of 2.88-7.6 cubic metres of concrete and 0.27-0.52 cubic metres of the shims per 1 metre of the length of the mine working. Within the coal industry of the USSR, the block roof support has been typed; the cross sections of the major horizontal and inclined mine workings with the block roof support are prescribed by the GOST governmental standard.
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