Click image to view full size image
Rock Bolts is a rod-like body anchored to the inside of a rock mass. The use of bolts to support the roadway is to drill holes in the surrounding rock after the roadway is excavated, and then the bolts are installed in the bolt holes to manually reinforce the surrounding rock of the roadway.
Â
Â
Saving pit wood and steel, reducing support costs, small excavation section, small deformation of roadway, low maintenance costs, work safety, lightweight, can reduce manual labor, reduce ventilation resistance, is conducive to a roadway construction and speed up the tunneling speed, wide range of use, strong adaptability, reduce the amount of transportation, is conducive to the transportation and lifting of the mine. But the bolt can not prevent the weathering of the surrounding rock, can not completely prevent the spalling of the fracture rock between the bolt and the bolt, therefore, the bolt with other support measures, such as with the metal mesh, shotcrete or shotcrete and other combined use, will achieve better support effect.
Â
Â
(1) Suspension: The anchor hangs the weak rock layer on the solid and stable rock layer above to prevent the separation from falling off. The direct roof of the coal seam roadway is generally weak and thin, and it is easy to fall off the layer, while the old roof above it is relatively strong. The anchor rod can reach the old roof through the direct roof, and the direct roof can be anchored on the old roof.
(2) Composite beam function: In the roadway roof of the layered rock layer, the thin layer of rock within the length of the anchor is anchored into a rock composite beam through a series of anchor rods, so as to improve its bearing capacity. Under the same load, the deflection and internal stress of the composite beam are greatly reduced compared with the uncomposite plate beam.
(3) Reinforcement of surrounding rock: the rocks in the deep surrounding rock of the roadway are in a state of triaxial compression, while the rocks near the periphery of the roadway are in a state of biaxial stress, and their strength is less than that of the former, so they are easy to destroy and lose stability. After the roadway surrounding rock is anchored by the anchor, the surface rock partially recovers the triaxial stress state, increases its own strength, in addition, the anchor can also increase the shear resistance of the weak surface of the rock layer, makes the surrounding rock around the roadway not easy to destroy and instability, which is called the surrounding rock reinforcement.
(4) Extrusion coupling: the bolt squeezes the surrounding rock of the roadway, applies prestress to the rock, prevents the continued expansion of the crack, and can also play the role of extrusion coupling and reinforcement for the loose rock. A simple and interesting experiment has been done abroad: a rectangular wooden box is used, filled with small gravel, and they are anchored with simulated anchors, and after the anchor rods are tightened, the wooden box is turned over, and the small gravel filled in it cannot be poured out. By prestressing the bolts, a lateral squeezing friction resistance can be created between the crushed stones that are not cohesive to each other, enough to support the weight of the crushed stones without falling off, as if the crushed stones were connected to each other.
Â
http://www.jnllky.com/