An expansion rock bolt is a double-layer concave tubular rod made of seamless steel pipes with an outer diameter larger than the anchor hole diameter. It was first developed in Sweden and has gained popularity in various engineering fields due to its unique principles and advantages. This article will introduce the principles, advantages, and applications of expansion rock bolts, providing a comprehensive understanding of this product.

Working principle of expansion rock bolt

Expansion rock bolt is composed of end sleeves, retaining rings, liquid injection ends and plates. When in use, insert the bolt into the borehole first, then inject high-pressure water to force the steel pipe to expand into a circular shape, and thus support the hole relying on the friction force between the expansion pressure of steel pipe and hole wall. It is temporary support when used in soft rock and broken zones, and it can be used as permanent support when used in hard rock.

Advantages of expansion rock bolts

Easy installation and immediate load-bearing

The expansion rock bolts the surrounding rock by injecting liquid into the inside of the rod to expand it. Its installation time mainly consists of two parts: liquid injection time and auxiliary time. Generally, the entire anchoring process can be completed in about 10 seconds by liquid injection. With the auxiliary operation time, the installation of an rock bolt can be completed in less than a minute, and it can realize the construction in a high position. Therefore, it is one of the rock bolts with the shortest installation time and is immediately load-bearing.

Full-length anchoring, uniform force, high anchoring force

The rock bolt has a higher anchoring force (generally above 80KN) under the condition of meeting the regular liquid filling pressure, and it is full-length anchoring, the whole of which expands and changes with the shape of the rock hole wall, and the force is uniform.

Safe and reliable

With high safety performance, it can effectively control the deformation of surrounding rock and guarantee construction safety.

Strong adaptability

Applicable to various geological conditions and engineering needs, good anchoring force effect in hard rock and corresponding deviation in soft rock.

Environmental protection and safety

The installation process generates no chemical or dust pollution, contributing to an improved working environment.

Expansion rock bolt applications

Expansion rock bolts are mainly used in hard rock mines, tunnels or emergency rescue scenarios. They can quickly provide support and achieve better support effects. Its excellent dynamic support effect meets the earthquake resistance requirements of support.

Construction technology of expansion rock bolts

1. Preparation

2. Drilling: Use a drilling rig to drill anchor holes according to design requirements to ensure that the hole diameter, depth, and position meet the requirements. During the drilling process,  the operator should pay attention to the control of drilling speed to avoid the hole wall roughness or collapse caused by drilling too fast.

3. Insert the expansion rock bolt: Insert the expansion rock bolt into the anchor hole to ensure the rock bolt position is correct and smooth. Then, water is injected into the rock bolt through a high-pressure grouting pipe, causing the rock bolt to expand and anchor to the hole wall. In this process, the operator needs to pay attention to controlling grouting pressure to avoid damage to the anchor rod or collapse of the hole wall due to excessive pressure.

4. Inject pressurized water to make the expansion rock bolt in contact with the hole wall, wait for the necessary time to let it completely unfold, and remove the nozzle of the inflatable pump.

5. Installation completed

Conclusion

As a new type of rock bolt, expansion rock bolt has significant application value. By understanding its many aspects, we can better realize its potential and further expand its applications in various engineering fields. With the ongoing development and enhancement of technology, it is believed that expansion rock bolts will play an increasingly significant role in future engineering construction.