Concrete roof support
CONCRETE ROOF SUPPORT (EN: concrete support, concrete timbering; DE: Betonausbau; FR: soutenement en beton; ES: entibacion de hormigon; RU: бетонная крепь) is the continuous solid mining roof support, which is made of concrete, and which is erected with the help of formwork. They use it for the roof support within the capital horizontal, inclined, and vertical mine workings, with service time of 10 years and more, and with stable evenly distributed rock pressure. Within the mine workings, with the angle of inclination of up to 40 degrees, and with the coefficient of the strength of the country rocks "f" of 3-9, they use the concrete roof supports with vertical walls and vaulted ceiling (Figure # 1a), but within the rocks with "f" of 1-2, and also in the case of the all-directional rock pressure and heaving soil, they make the enclosed roof supports, with inverted vault (Figure # 1b).
In case of the rock pressure, which is reaching 490 kilopascals, and also within the mine workings with the angle of inclination of more than 75 degrees, they provide the concrete roof support with the round or oval shape, and supply this roof support with the conical abutment crowns, which are installed, as a rule, with intervals of 30-60 metres. They erect the concrete roof supports usually at the certain distance behind the stope (within the rocks with the "f" of 0.4-1.5 at most 3 metres; with the "f" of 1.5-9 at most 20 metres), and in case of the inclined and vertical mine workings with the segments from the bottom up. They uphold the place between the stope and the place for the erection of the concrete roof supports by the temporary roof support.
The major operations for the erection of the concrete roof support are: the preparation of the concrete mixture, the delivery of this mixture to the place of the works, the construction of the formwork, the pouring, distribution, and compacting of the mixture into the formwork. Within the mine workings with constant cross section and large length, they use, as a rule, the mobile or inventory assembled metallic formwork. They prepare the concrete mixture mainly according to the centralized method at the surface, and are delivering this mixture within the special containers or through the pipes into the place for the laying, and place this mixture into the formwork according to the mechanized method with the usage of the concrete laying machines (Figure # 2).
The thickness of the concrete roof support depends on the size of the mine working, and on the strength of the rocks. Within the horizontal and inclined mine workings, the thickness of the vault at the keystone is at least 17 centimetres, the thickness of the wall is at least 20 centimetres, and within the vertical mine workings, the thickness of the wall is at least 30 centimetres. The consumption of concrete per 1 metre of the horizontal and inclined mine workings is 1.52-8.42 cubic metres. Within the coal industry of the USSR, the concrete roof supports are typed according to standards.
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