The magnitude of the force of the single-pillar is determined first by the pressure of the top plate, and sometimes by the mechanical properties of the bottom plate and whether the top beam is compressible. The distribution of the load on the single struts on the beam depends on how the top beam is placed on the struts, as shown in Figure 5-7. If the connection is in good condition, the length of the front and rear beams is 1:1 based on the pillars, and the load should be evenly distributed, as shown in figure a. If there is a certain deformation at both ends of the top beam, it should be parabolic, as shown in Figure b. If the ratio is 2:1, it is a triangle distribution, as shown in c. It is preferable that the ratio of the front and rear beam lengths is not more than 2, because, in fact, the excess part of the beam does not support the top plate, as shown in the figure d.
Figure 5-7 Load distribution of the top beam of the single pillar
When starting to use all the slumping methods to treat the goaf, the bracket is divided into two parts: the working surface bracket and the cutting top bracket. The arrangement is shown in Figure 5-8. Its principle is to use the working face bracket to maintain the integrity of the direct roof, and use the cutting top bracket to cut the direct top along the goaf, and also has a control torque for the basic top. This type of support is also known as the top of the column. The top of the column is not shown in Figure 5-9.
Figure 5-8 Supporting force distribution of a row-column top-mounted support Figure 5-9 No-column topping and support force distribution
(one) Â Hooded column support
Used when the direct top is relatively complete. The column caps are generally made of wood or semi-round wood with a thickness of 50 to 100 mm and a length of 0.3 to 0.5 m. There are two types of hooded post on the working surface: rectangular arrangement and triangular arrangement, see Figure 5-10.
Figure 5-10 Arrangement of the cap with a cap
(a)--Rectangle arrangement; (b)--Triangle arrangement
Should be considered a pillar erected angle coal layer, should generally upwardly inclined 2 ~ 4 o.
(two) Â Shed support Â
When going to the shed, when the pressure on the roof is large, a chain-type shed can be used. When the roof pressure is small, the docking type can be used. When the joint fissure is perpendicular to the work surface, an inclined shed is used.
(three) Â Unit working plane single bracket arrangement
1 Relationship between cantilever beam and pillar
In combination with a strut hinged metal roof beam as outriggers. According to the arrangement of the cantilever bracket along the direction of the working surface, it can be divided into two types: the cantilever type and the inverted cantilever type, as shown in Figure 5-11.
Figure 5-11 Cantilever support of the working face of the unit
(a) - positive cantilever; (b) - inverted cantilever
When the front cantilever is used, the top plate of the machineway can be supported by cantilever. If necessary, the beam can be hung in advance to hang the beam, and the help column can be applied. Therefore, the safety condition of the machine path is better. When erecting the cantilever beam, the tongue end should face the coal wall so that the beam socket can be smaller when the truss beam is required. In this way, the cantilever beam does not protrude from the side of the goaf, and thus is not easily broken.
When the inverted cantilever is used, the pillars on one side of the goaf are retraced and are not easily buried by the meteorites. When the top plate is relatively broken, the truss nest is relatively shallow, so it is easy to hang the beam. This way it is safer to return to the column.
2 The arrangement of the brackets is two types: beam beam type and wrong beam type.
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