Application of anchor spray net support technology in reinforcing dynamic pressure roadway
Dynamic pressure or dynamic pressure refers to various concentrated pressures due to mining activities, including the concentrated concentrated pressure on the working face, the concentrated pressure on the roof, the one-sided coal column pressure on one side, and the two sides on both sides. Concentrated pressure, as well as other superimposed pressures. Dynamic pressure roadway generally refers to the underground roadway that is affected by mining. Its characteristics are as follows: the steady state of the mine pressure at the roadway is affected by mining, which breaks the original stability of the surrounding rock and causes the surrounding rock stress to be redistributed again or repeatedly. The stable balance under the original static pressure state is broken, and the surrounding rock undergoes significant deformation, displacement and pressure increase. After the stress redistribution reaches a new equilibrium, the surrounding rock of the roadway can be stabilized again. If the support of the roadway cannot adapt to the stress change caused by the mining effect, or if the corresponding reinforcement and remedial measures are not taken in time, the roadway will be damaged to varying degrees, or the section deformation, or the surrounding rock loose and unstable, even the gang, Roofing seriously affects the normal and safe use of the roadway. Second, the anchor net spray support mechanism The anchor spray net support can fully exert the role of the bolt and fully exert the effect of the shotcrete. At the same time, the mesh completes the fracture ring on the surrounding rock surface, makes the spray layer even and even, increases the bending and shear resistance, and has higher flexibility and larger allowable deformation. The anchor spray net support breaks through the traditional old support form and support theory. It does not negatively support the loose surrounding rock, but actively maintains the integrity and stability of the surrounding rock and controls the surrounding rock deformation, displacement and fracture. Develop and give full play to the supporting role of the surrounding rock itself. That is to protect the main, supplemented by the support, is a kind of support form that is more reasonable and suitable for supporting the loose ring and supporting the unstable rock. 1 anchor action Through the extrusion and reinforcement of the anchor rod, a certain thickness is formed in the surrounding rock, and the compression belt is evenly connected, that is, the extrusion reinforcement effect, which not only maintains its own stability, that is, the anchor-surrounding rock collectively carries the combined arch, and can withstand Ground pressure prevents the loosening and deformation of the surrounding rock. 2 shotcrete effect (1) Close the surrounding rock in time, strengthen the weathering prevention, increase the strength of the surrounding rock, and prevent the surrounding rock from being damaged and peeled off due to water and weathering. (2) Improve the surrounding stress state, increase the strength, fill the open joints, cracks, and consolidate the surrounding rock to strengthen the role. (3) Acting as a flexible supporting structure, the shotcrete and the surrounding rock are closely bonded together, and when the thickness is not too large, it is flexible, can be displaced along with the surrounding rock, and generates a supporting reaction force during the displacement process. . (4) The adhesion and shear strength of the spray layer to the rock can be sufficient to resist the local damage of the surrounding rock and prevent individual dangerous rock from moving, slipping or falling. (5) Forming a combined arch effect, the shotcrete joins the broken rock mass into a whole, forming a load-bearing structure, thereby isolating the deep deformation of the surrounding rock to achieve a three-direction stress state. 3 metal mesh (1) Laying the metal mesh correspondingly increases the surface of the anchor pallet, thereby changing the point anchoring of the original roadway wall, and is a full-area anchoring extrusion. In the case where the length of the anchor is the same and the density is the same, the thickness of the extruded reinforcing arch is increased, and the ability of the roadway to resist damage is improved. (2) The ability of the spray layer to shear and tensile is improved, and the support strength of the spray layer is enhanced. (3) The spray layer and the metal mesh are firmly combined by the anchor rod and the metal mesh, so that the spray layer and the surrounding rock are not easily separated from the layer and fall off. 3 Selection of support parameters 1 anchor length: L=N(1.1+B/10)=1.2×(1.1+3.2/10)=1.7m Anchor spacing: D≤0.5L=0.5×1.7=0.85m B-wayway span, 3.2m The influence coefficient of N-surrounding rock stability, the coefficient of surrounding rock of class V is 1.2. According to the above calculation results, the bolt specifications: high-strength threaded anchors of φ16×2000mm, 10 per row, 900mm spacing, spacing 850mm, 1000mm, anchor resin roll specifications: φ25×49mm, 1 roll per eye , plate specifications: diameter 160mm, thickness 10mm circular pallet, using φ32mm drill bit for eye construction. 2 metal mesh selection conditions (1) The mesh ribs must meet the requirements of strength and rigidity, and have certain shear and bending resistance. (2) Manpower can make the metal mesh bend along with the tunnel arch, and it can be closely attached to the tunnel wall after being anchored by the anchor. (3) The mesh should not be too small, so as to avoid voids appearing behind the net during sneezing, affecting the strength of the carcass. (4) The size of the mesh is suitable. It is easy to operate in construction. Therefore, the metal mesh specification is 1.5×1.2m, the mesh specification is 80×80mm, and the steel bar diameter is 4mm. The net should be laid flat and close to the rock wall. To ensure that overlapping metal mesh, for web adjacent sides rod hook for hooking connected, and then connected to the solid filament φ10 iron, and finally pressed metal pallet. 4 shotcrete (1) Selective thickness of shotcrete. If the sprayed layer is too thin, it will affect the strength of the support. If the thickness is too thick, it will affect its flexibility, increase the brittleness, and easily separate the surrounding rock, so that the bearing structure formed by the surrounding rock cannot be maintained. According to the service life of the roadway, the span, the stability of the surrounding rock and the actual experience of the mine, the thickness of the shotcrete is determined to be 100mm. The secondary shotcrete is divided into four parts, the initial spray thickness is 40mm, and the double spray is up to 100mm thickness. (2) Requirements for shotcrete materials. Ordinary Portland cement with a strength of 42.5 is used, medium sand with a particle size of 0.3mm ~ 3mm, the diameter of the stone is not more than 25mm, cement: sand: stone = 1:2.5:1.5. (3) Shotcrete parameters. Rotary type ZHP-2 concrete shotcrete machine is used, the working pressure is 0.12 MPa ~ 0.18MPa, the distance from the nozzle to the spray surface is 1m ~ 1.5m, the length of the feed pipe is 20m, and the quick-setting agent is controlled within the range of 3% ~ 5%. Take a small value when the two walls are used, and take a large value when spraying the vault, and make the tide mix, sprinkle the water before the spray, reduce the rebound and dust, and ensure the strength of the concrete. Fourth, anchor construction From the top position of the roadway to the two sides as required, the installation of the anchor rod and the anchor rod eye crossover is required. After each eye bolt is installed in place, the torque is manually added to ensure that the torque of each bolt is not less than 200kN, the anchor rod The anchoring force is not less than 5t. Hanging nets began with two gangs, first hitting temporary support, and then removing the original metal shed legs. V. End theory The roadway is reinforced with anchor spray net support technology. After two years of use, the roadway is intact, without deformation, carcass falling off, and chipping. Practice has proved that the use of anchor spray net support technology in dynamic pressure fracture zone is feasible. Compared with U-shaped steel shed and bricklaying, it has the advantages of simple process construction, lighter labor intensity, safe construction and no maintenance during use. It is an active support that is a flexible support that combines "resistance" with "let". Pallet trucks Manufacturer test cushi , http://www.sitez.com