What Is Rock Bolt? Common Types and Applications

The emergence of rock bolts has greatly improved the safety of the mining and underground excavation industry. Rockfall and collapse are the crucial reasons for the failure of underground engineering and the high mortality before the development of ground support technology. It was not until the late 19th century that steel rock bolts were first used in mining. Up to now, rock bolt has been widely used in the construction of foundation support, tunnel excavation, and other projects for economical and high-safety features.

Rock bolt reinforcement can improve the strength and self-stability of rock mass, effectively control the deformation of geotechnical, and has a positive effect on the stability of tunnel excavation. The use of rock bolts in geotechnical engineering has become one of the most economical and effective methods to improve the stability of geotechnical engineering and solve complex engineering problems. This article will introduce the definition of rock bolts, types of rock bolts, and related application scenarios.


What Are Rock Bolts?

Rock bolts are steel threaded rods that are inserted into rock mass to stabilize underground rock and soil structures during excavation. In simple terms, rock bolt is embedded in the rock and can bear the tension of the rod.

The anchorage structure formed by a rock bolt adopts a prestressed bolt group, which can transfer the tensile stress of the structure to the deep stable strata or reinforce the unstable rock mass, and form a bearing structure system in which rock bolt and rock mass interact and work together.


Types of Rock Bolts

Self-drilling rock bolt

self drilling rock bolt

Currently, the widely used mortar bolt is easy-to-use and low cost for construction.

However, there may be safety hazards in the engineering quality when the ordinary mortar bolt is used. Usually, the grouting step is before the mortar bolt insertion, and as a result of this process, human factors have a great impact on the filling degree of grouting and the final anchorage length is often far from the design requirements.

Compared with the general mortar bolt, the self-drilling rock bolt developed rapidly in recent years and has obvious advantages. The self-drilling anchor system is composed of a hollow anchor bar, nut, plate, coupler, centralizer and drill bit. It combines drilling, grouting, and anchoring functions together, which is suitable for broken rocks and surrounding rocks that are difficult to drill holes. At present, the self-drilling bolt is suitable for broken rock, loose rock, and other geology that is difficult to form holes and easy to collapse. It can greatly improve the supporting effect in complex geology and achieve the best construction effect.

At present, Sinorock self-drilling anchor system has been widely used in many tunnel and slope projects, showing broad development prospects.


Expansion Shell Hollow Anchor Bar

The expansion shell hollow anchor bar consists of a hollow anchor bar, plate, nut, and expansion shell. The expansion shell hollow anchor bar can be prestressed and can be adjusted by applying a torque wrench. The bolts are typically 1 to 5 meters in length and carry capacities from 100 to up to about 500KN. Mainly used in mining and tunnel systematic support.



Swellex-anchor, also known as hydraulic expansion bolt, is composed of end sleeve, retaining ring, liquid injection end, tray and other accessories. The Swellex-anchor is unique. It needs to put the bolt into the bolt hole and then use high-pressure water to make it expand. In the expansion process, the water-swelling bolt will produce permanent deformation, and the pipe wall will completely fit the irregular hole wall of the bolt hole. Friction and self-locking force are generated throughout the whole length of the bolt, thus strengthening the rock mass. Due to its quick installation, safety, reliability and high flexibility, the swellex-anchor has been widely used at present.


Rock Bolt Application

1.    Spiling

2.    Fore-poling

3.    Radial systematic anchoring

4.    Root piling

5.   Stabilization of tunnel portals

rock bolt applications


How to Install Rock Bolt?

Take the self-drilling anchor bolt as example:

1. Preparation.
Check that the rig is functioning properly and that the drill bit and bolt are not damaged. After checking, install the drill bit and connect the rod to the drilling rig.

2. Drilling test. Drilling at different angles (such as 20°-30° angle, vertical angle) to test the drilling conditions of different construction geology.
3. Simultaneous drilling and grouting. Adjust to a suitable angle, start the drilling rig, and the grouting is completed synchronously when the drilling is completed.
4.  Install the flat plate and nut.



The above describes the common types and application scenarios of rock bolts. As a new anchorage technology, self-drilling bolt greatly improves the efficiency of construction. As a professional provider of self-drilling anchorage system solutions, Sinorock has a professional technical team, which can provide customized product solutions according to customer requirements. Welcome to contact: sinorock@sinorockco.com

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