What are the functions of the bolt support combination?

1. Suspension effect.

Bolt support. The suspension effect, the outstanding performance in the case of the direct top is thinner and the old roof is stronger, the anchor will suspend the lower unstable rock layer on the stable rock layer on the upper step, and the anchor bears the weight of soft rock or dangerous rock to achieve the purpose of shaft stability. Practice has proved that even if there is no stable rock formation in the upper part of the roadway, the bolt can play a supporting role.

For example, in the all-coal roadway, the anchor rod can also be anchored in the coal seam to achieve the purpose of support.

Second, the composite beam role of the anchor.

In order to solve the limitations of the suspension theory, the composite beam theory is proposed in the layered strata. The composite beam theory is suitable for the roadway where the roof is composed of multiple layers of continuous rock layers with small thickness, and its principle is that in the thin layered rock layer where there is no stable rock layer to provide a suspension fulcrum, the tensile force of the anchor rod can be used to combine the layered strata to form a composite beam structure for support. And with the help of the bolt itself, it provides a certain shear resistance to prevent its interlayer dislocation, which is to prevent the overall bending deformation of the layer under the action of pressure, showing a combined state, so as to improve the bending stiffness and strength of the roof.

The main factors determining the stability of the composite beam are the pretensile stress of the anchor, the strength of the rod and the properties of the rock formation.

1. The span reduction effect of the anchor.

If the unstable roof rock layer is regarded as a superimposed beam supported in two gangs, because the anchor rod hanging on the old roof is the fulcrum, the installation of the anchor rod is equivalent to increasing the fulcrum, thereby reducing the span of the roof, reducing the bending stress and deflection of the roof rock layer, and maintaining the stability of the roof. This is the span reduction effect of the bolt, and this set of theories is actually the suspension effect of the anchor.

2. Reinforcement arch effect.

For the block or fractured surrounding rock cut by the criss-cross weak surface, if it is reinforced with anchors in time, the shear strength of the weak surface of the rock mass structure can be improved, and a reinforcing arch that can not only maintain its own stability, but also prevent the loosening and deformation of the upper surrounding rock can be formed within a certain thickness range around the surrounding rock, so as to maintain the stability of the roadway.

The mechanical state of the surrounding rock itself is changed by the anchor inside the surrounding rock, and an integral and stable rock belt is formed around the roadway, and the anchor rod and the surrounding rock are used to work together to achieve the purpose of maintaining the stability of the roadway.

Bolt support. The rod column is made of metal parts, wood parts, polymer parts or other materials, driven into the pre-drilled hole of the surface rock mass or the rock mass around the chamber, and the special structure and tail supporting plate of the head and rod body are used, or the surrounding rock is combined with the stable rock mass by relying on the bonding effect to produce the suspension effect, the combined beam effect and the reinforcement effect, so as to achieve the purpose of support.

Bolt type. 1. Full-length bonded anchor: ordinary cement mortar.

Anchors, early-strength cement mortar bolts, resin coil bolts, cement coil bolts.

2. The end is anchored.

Type anchors: mechanical anchor bolts, resin anchor bolts, fast-hardening cement, coil anchor bolts.

3. Friction anchors: seam pipe anchors, wedge pipe anchors, and water expansion anchors.

The above content refers to Encyclopedia - Bolt Support.

Bolt support refers to a reinforcement support method used in surface engineering such as slopes, deep geotechnical foundation pits, tunnels, stopes and other underground chamber construction. The rod column is made of metal parts, wood parts, polymer parts or other materials, driven into the pre-drilled hole of the surface rock mass or the rock mass around the chamber, and the special structure of the head and the rod body and the tail supporting plate (which can also be omitted), or rely on the bonding action to combine the surrounding rock with the stable rock mass to produce the suspension effect, the combined beam effect, and the reinforcement effect, so as to achieve the purpose of support. It has the advantages of low cost, good support effect, easy operation, flexible use, and less clearance for construction.

Bolt support is a component of anchor spray support, is a rod body anchored in the rock mass, through the anchor into the rock mass of the steel bar and the rock mass integration, to improve the mechanical properties of the surrounding rock, adjust the stress state of the surrounding rock, inhibit the deformation of the surrounding rock, to achieve the purpose of strengthening the surrounding rock, and maintaining the stability of the surrounding rock. The suspension, combination, span reduction and extrusion reinforcement of the bolt are used to string the joints and fractures in the surrounding rock into one to improve the integrity of the surrounding rock.

First, the suspension effect: the anchor rod 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.

Second, the function of the composite beam: in the roadway roof of the layered rock formation, through a series of anchors of the anchor, the thin layer of rock within the length of the anchor rod is anchored into a rock composite beam, 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.

Fourth, extrusion coupling: the bolt will squeeze the surrounding rock of the roadway, apply prestress to the rock, prevent the continued expansion of the crack, and can also play the role of extrusion coupling and reinforcement for loose rock. A simple and interesting experiment was done abroad:

Use a rectangular wooden box, fill it with small gravel, and anchor them with a simulated anchor, after the bolt is 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.

Anchor is the most basic component of roadway support in contemporary coal mines, which binds the surrounding rock of the roadway together and makes the surrounding rock support itself.

Now bolts are used not only in mines, but also in engineering technology, for active reinforcement of slopes, tunnels, dams.

As a tensile member that penetrates deep into the formation, one end of the bolt is connected with the engineering structure, and the other end goes deep into the formation, and the whole anchor rod is divided into a free section and an anchor section, and the free section refers to transmitting the tensile force at the head of the anchor rod to the anchor solid area, and its function is to apply prestress to the anchor rod; The anchoring section refers to the area where the cement slurry bonds the prestressed tendon with the soil layer, and its function is to increase the bonding friction between the anchor solid and the soil layer, increase the bearing effect of the anchor solid, and transmit the tensile force of the free section to the depth of the soil.

Anchors can be divided into wood bolts, steel bolts, FRP bolts and so on according to the materials used.

According to the anchoring method, it is divided into: end anchorage, extended anchorage and full-length anchorage.

Here are a few of the names of anchors.

1) Wooden anchors. There are two kinds of wood anchors used in our country, namely ordinary wood anchors and compressed wood anchors. �

2) Steel bar or wire rope mortar anchor. The cement sand paddle is used as the binder between the anchor rod and the surrounding rock. �

3) Inverted wedge metal bolts. This type of bolting was once one of the most widely used forms of anchoring. Because it is simple to process, easy to install, and has a certain anchoring force, this anchor rod is still in use in a certain range. �

4) Pipe seam anchor. It is a full-length friction anchor bolt. This bolt has the characteristics of simple installation, reliable anchoring, large initial anchor force, and long-term anchoring force increases with the movement of surrounding rock. �

5) Resin anchors. Using resin as a binder for anchors is costly. �

6) Fast hardening expansion cement anchor. It is made of ordinary Portland cement or slag Portland cement with admixtures, which has the characteristics of rapid setting, early strength, water reduction and expansion

7) Double fast cement bolts. It is made by mixing finished early-strength cement and double-fast cement in a certain proportion. It has the characteristics of fast hardening, fast setting, and early strength.

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The pro-anchor support can play the role of suspension, composite beam, combined arch, span reduction wheel, and reinforcement. The bolt is the most basic component of roadway support in contemporary coal mines, and he reinforces the surrounding rock of the roadway together, so that the surrounding rock supports itself. Now the bolt is not only used in the mine, but also used in engineering technology to strengthen the main body of the slope, tunnel and the dam body.

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