Research on truss anchor belt network support in fully mechanized caving mining roadway

1, of the problem Yanzhou Coal Mining Bureau thick layer of fully mechanized longwall top since 1992 in Xing successful, due to the high production efficiency, low cost and safety advantages of coal thickness can adapt to change, showing strong vitality, Rapid development into the main coal mining method of the bureau. There have also been many new problems in the development process, and the problem of mining roadway support is one of them. The bureau now generally adopts trapezoidal miner steel shed support, which is mainly incompatible with the fully mechanized caving mining method. (1) The mining roadway has a large workload and long occupation time, which directly affects the work. The rapid advancement of the fully mechanized caving face and the further development of the high-yield and high-efficiency capacity; (2) The active surrounding rock should not be actively reinforced and the self-supporting ability of the surrounding rock should be fully utilized, so that the top of the excavation is severe and the top coal spontaneous combustion occurs; (3) The area shrinkage rate is large It does not meet the requirements of ventilation, transportation and equipment handling and installation in fully mechanized caving mining method; (4) high consumption of steel and high cost of support; (5) serious deformation of shed and surrounding rock, large maintenance workload, and occupation of personnel (6) The end maintenance worker has a high labor intensity, and the personal safety hazard for the shed work is large. In response to the above problems, we propose a new type of support - truss anchor belt mesh support. 2, truss anchor belt network support principle The key component of truss anchor belt network support is truss anchor. The truss anchor generally consists of two roof inclined anchors and a horizontal tie rod and tray, as shown in Figure 1. Under the action of the inclined anchor rod and the horizontal tie rod, the truss anchor support system produces compression and topping action on the middle part of the top plate, which increases the compressive stress and friction force in the top plate crack body, and reduces or even offsets the possibility of the middle part of the top plate. Pulling stress. The two inclined anchor rods are coordinated by the tie rods and have certain flexibility, which allows the top plate to sink in an appropriate amount. During the sinking process, the friction of the top plate crack body increases, resulting in a self-locking effect, thereby effectively maintaining the fracture of the high stress area. roof. And the role of steel metal mesh is to increase contact between the monomer bolt, bolt to prevent loosening between cave surrounding rock.

3. Research on truss anchor belt network support in fully mechanized caving mining roadway The study of the fully mechanized caving mining roadway in the mining area of ​​Xinglongzhuang Mine is based on the numerical simulation method (FLAC software). 3.1 Numerical simulation of surrounding rock stability and section aspect ratio is limited to rectangular and trapezoidal sections with a sectional area of ​​12 m2. The simulation analysis of seven rectangular sections with an aspect ratio of 0.47, 0.67, 0.75, 0.84, 0.91, 1.33 and 2.08 shows that the reasonable aspect ratio is 0.75. Further, a trapezoidal section with a width of 3.4 m, a width of 4.2 m, a height of 2.8 m and an average aspect ratio of 0.75 is shown to indicate that the trapezoidal section is superior to the rectangular section. 3.2 System bolt support parameters and surrounding rock stability literature studies have shown that for soft rock test blocks with a modulus of 5. 4GPa, the reasonable parameters of the system anchors are: L/e and e<0.9-1.2m ( L is the length of the bolt and e is the bolt spacing). The elastic mode of the coal body is generally less than 5.4 GPa, and the arrangement of the system anchor to strengthen the coal body can refer to the value of the range. In order to specifically determine the L, e and L/e values, the 16 system bolt support schemes listed in Table 1 were simulated. The results show that the scheme 6 is L=2. lm, e=0. 7m, L/e=3.0.

3.3 The relationship between the sinking amount of the roof (u) and the inclination angle of the truss anchor (α) and the preload of the tie rod (T) is to study the variation of the sinking amount of the roof with the inclination of the truss anchor and the preload of the tie rod, simulating the truss anchor There are 8 cases of inclination angles of 40o, 45o, 50o, 55o, 60o, 65o and 70o and 8 schemes of lever pre-tightening force from 0KN, 10KN, 20KN, 30KN... to 90KN. The results show that reasonable truss anchors The inclination angle α=15o-60o, the suitable truss tie rod pre-tightening force T=40-50KN. 3.4 The relationship between the amount of convergence of surrounding rock and the prestress of F is to study the change of the top and bottom of the fully mechanized caving mining roadway and the change of the two gangs with the prestress of the bolt, and simulate the prestress of the bolt. 7 cases at 0kN, 10kN, 30kN, 50kN, 70kN, 90kN and 110kN, the results are shown in Figure 2. When the prestress of the bolt is F<60-70kN, the increase of the prestress has a significant effect on the surrounding rock control effect; on the contrary, the control effect on the surrounding rock is not obvious, so the suitable prestress of the anchor is 60~70kN.

3.5 truss strip network support system parameters According to the numerical simulation results, the truss anchor belt network support scheme for the fully mechanized caving mining roadway is designed, as shown in Figure 3.

The parameters of the truss anchor belt network support system are as follows: (1) Roof truss anchor support parameters: 1 truss anchor: Ф20, length 2.35 deformed rebar, inclination angle 55o; 2 anchoring method: resin coil lengthening anchor (using K2335 And each of the Z2370), 3 tie rods: two pieces of Ф14 round steel each, 2.5m long; 4 truss tray: cast with ZG270-500 material. (2) Roof steel with bolt support parameters: 1 steel belt anchor: Ф2.0, length 2.0m deformed rebar, inclination angle 70o, 80o, 90o, anchor spacing 700mm, row spacing 1.4m, anchoring The same way as the truss anchor; 2 steel belt: BHW-280-3-3400W steel strip (transverse) and BHW-280-3-850W steel strip (longitudinal); 3 pallet: BHT-B casting pallet; ④ metal: using 10 # 60 × 80mm, is 3600 × 800mm mesh diamond mesh iron. (3) Two sets of support parameters: 1 set of anchor rods are made of Ф20, 2.0m long deformed rebar, with a row spacing of 700×700mm; 2 anchoring mode: fast hard cement roll full-length anchoring; 3 tray: used in The wooden pallet is matched with a metal tray, and the size of the wooden pallet is 500×200×50 mm.

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