Why Should We Use Self-drilling Rock Bolt to Support the Weak Rock When Excavating A Tunnel?

Time:2022-02-15From:sinorock View:

During tunnel excavation, we often encounter weak rock. Due to the potential danger of this kind of rock, under normal circumstances, we will use self-drilling rock bolts to support it to ensure construction safety.

What is a weak rock? What are the characteristics of weak rock?
What are the support methods for weak rock? What are the characteristics of each?
What are the characteristics of self-drilling rock bolts? What are the advantages of self-drilling rock bolts for supporting weak rock?
How to construct self-drilling rock bolts?
Why use self-drilling bolts to support the weak rock of the tunnel?

What is weak rock? What are the characteristics of weak rock?

The weak rock in the tunnel mainly refers to the V-level rock and the W-level rock. This type of rock is characterized by more joints than cracks, full weathering, broken rock mass, loose structure, poor stability, easy to collapse, and some of them contain a lot of water. If it is not supported, there will be falling blocks or even collapse during the construction process. It not only affects the work of workers but also threatens the personal safety of workers.

What are the support methods for weak rock? What are the characteristics of each?

Advanced long pipe shed: It is mainly composed of a pipe shed and steel frame to form a pre-support system to support and reinforce the rock and prevent the weak rock from sinking, loosening, and collapsing. This method has a good support effect, but high cost and low efficiency, and the overall progress of the project are slow.

Leading small pipe: It can reinforce the rock in a certain range of the cave wall, and can also form a small pipe shed system with a steel frame to support the rock. This support method can greatly improve the construction efficiency, but when encountering relatively broken rock formations, the construction effect is unsatisfactory.

Advanced double-layer small duct: similar to the advanced small duct, the difference is that the small ducts are arranged in a double-layer staggered arrangement. The effect of this support method is relatively good, but the cost is high, the efficiency is low, and the grouting effect is difficult to guarantee.

Advance pre-grouting: Consolidate the rock mass through pre-grouting, improve the bearing capacity and self-stabilizing ability of the rock, and at the same time achieve the effect of water blocking. This method has high construction efficiency and low cost. The main defect is that the grouting effect is not good, and the grouting amount cannot be guaranteed, so the reinforcement quality cannot be guaranteed.

What are the characteristics of self-drilling rock bolts?

The self-drilling rock bolt is composed of a hollow anchor bar, coupler, nut, drill bit, plate, and centralizer. It can combine drilling, grouting, and anchoring in one process. The self-drilling rock bolt system is safe, efficient, and convenient. It is suitable for broken rock, loose soil, and geological conditions where is difficult to drill holes. It helps to ensure the anchoring effect in complex ground conditions and achieve the best construction result.

What are the advantages of self-drilling rock bolts for supporting weak rock?

Self-drilling rock bolt, which combines drilling, grouting, and anchoring together, is suitable for broken rock and conditions which are difficult to drill holes. Casing pipe is omitted in construction, which greatly improves construction efficiency.

Self-drilling rock bolt can fill cracks, consolidate rock mass and soil layer through pressure grouting, and has good grouting spreading radius and reliable anchoring quality.

The hollow anchor bar can be cut arbitrarily and lengthened by the coupler. Therefore, a self-drilling rock bolt is suitable for construction in the narrow space which the large equipment can not enter.

How to construct self-drilling rock bolts?

Pre-construction preparation: Prepare the equipment and materials required for construction such as rock bolts, drilling rigs, grouting machines, and anchoring agents. The grouting machine starts to prepare the grout and check whether the grouting pipeline is unobstructed.

Drilling and grouting construction: Connect the grouting pipe to the drilling rig through the rotary grouting adapter, install the anchor rod, and start the drilling and grouting construction.

Why should we use self-drilling rock bolts to support the weak rock of the tunnel?

In tunnel support construction, after comparing the above methods, it is not difficult to find that self-drilling rock bolt support has many advantages, such as high construction efficiency, low comprehensive construction cost, and good operability in narrow space construction. Therefore, the self-drilling rock bolt support is the best support method for the weak rock of the tunnel.

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