The mining face bracket is mainly composed of a combination of beams and columns. According to the cooperation relationship between the pillar and the top beam, the mining face bracket can be divided into two categories, namely, a single bracket and a hydraulic bracket. Face bracket made of a metal and a metal strut hinged roof beams called tubbing combination, depending on the characteristics of the metal posts, and can be divided into frictional metal stent and the monomer hydraulic support, the former used is a friction strut Metal pillars, the latter being hydraulic pillars. The hydraulic support is a structure in which the pillar, the base and the top beam are combined as a whole. It is powered by hydraulic pressure, which not only realizes the automation of support and withdrawal, but also realizes mechanization in a series of processes such as shifting and sliding, which fully reduces the heavy manual labor. P' 0 — initial support. When the bracket is supported, the column is raised, the top beam is supported, and the pillar is used to generate a main power to the roof by using the lifting tool and the locking device. The primary power that was originally formed is called the initial support of the pillar. For the hydraulic strut, it is the supporting force of the pillar formed by the pumping pressure on the top plate. P 0 — Starting resistance. At the moment when the living column begins to shrink under the action of the roof pressure, the force reflected on the pillar is called the starting resistance. This force is formed by the top plate compression struts. So called the resistance of the pillars. P 1 — Initial work resistance. In the performance curve of the bracket, when the living column is shrunk, the growth rate of the working resistance changes from a sharp increase to a working resistance at a slowly increasing turning point. P 2 — Maximum working resistance. The maximum load capacity that the pillar can withstand, also known as the rated working resistance. The working characteristics of the pillars currently used are as follows, as shown in Figure 5-12. Figure 5-3 Several typical characteristic curves of the strut ( P -Δ S curve) (a)  - sudden increase in resistance; (b)  — micro-resistance; (c)  — constant resistance; P' 0 — initial support force; P 0 — starting resistance; P 1 — initial working resistance; P 2 — rated working resistance or maximum working resistance. Augmented resistance type - when the pillar starts to support, there is a very small artificial initial force P' 0. When the pillar is under the pressure of the roof, the starting bar is formed, and the starting resistance P 0 is formed . As the living column is shrunk, the working resistance increases linearly. This type of pillar can be reduced in size. Its characteristic curve is shown in Figure 5-3(a). Micro-increasing resistance - just like the sudden increase resistance, only has a small initial force and starting resistance. But with the shrinking of the living column, the working resistance has a sharp growth process. When the initial working resistance P 1 is reached, as the strut continues to contract, the increase in working resistance becomes extremely slow, up to the maximum shrinkage of the strut, which is the maximum working resistance of the strut. Such pillars have a large shrinkage, and their characteristic curves are shown in Figure 5-3(b). Constant resistance type - When the pillar is installed, as the living column is shrunk, the rated working resistance is quickly reached. After the living column continues to contract, the working resistance of the pillar remains unchanged. The characteristic curve is shown in Figure 5-3 (c ). From the analysis of the working resistance of the pillar to adapt to the characteristics of the roof pressure, it is obvious that the pillar of the constant resistance performance is more favorable, and the sudden increase performance is relatively poor. However, the structure of the constant resistance pillar is relatively complicated and the cost is high. The structure of the sudden increase resistance is simple and the cost is low. A&M Manufacturing Co. Ltd. is a
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