Hollow Rockbolt

What Is Self-drilling Hollow Rock Bolt?

Weak and broken surrounding rocks are often encountered during construction in tunnel engineering. Due to the nature of the rock mass itself, the weak and broken surrounding rock is easy to collapse and difficult to form holes, and it is difficult for ordinary bolts to support. So we recommends the use of self-drilling hollow rock bolts.

The self-drilling hollow rock bolt system 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 anchor 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.

Reinforcement of hard rock strata as well as soft strata for preventing rock collapse is carried out using support systems incorporating rock bolts. The rock bolts are inserted into holes drilled into rock and secured there by resin or cement based grout applied in the holes.

To consolidate the separate steps of drilling a hole in rock then inserting and fixing a rock bolt in the drilled hole, self drilling rock bolts are used. Self drilling rock bolts can be drilled into rock and anchored therein in onepass.

Self-drilling hollow rock bolts function by utilizing the sacrificial drill bit to penetrate hard rock or soil, creating a path for the subsequent grouting process. As the bolt advances, it effectively fills the void with grout, providing reinforcement and stability to the surrounding structure or geological formation. This integrated approach to drilling, grouting, and anchoring enhances construction efficiency and ensures reliable structural support.
 

how to install the hollow rock bolt

 

1. Connect the alloy drill and anchor rod one end, on the other end, connect the drill sleeve and shank adapter ,then connect the drilling rig or hand-held drill. Then start drilling, fill the cooling water while drilling.( If you want to lengthen the anchor rod, can connect the coupling, and then drilling)

2. Take down the drill, put the stop-grouting plug into the rod, and insert it to the hole, then ready to grout. Special circumstances like surrounding rock
grouting tension is over or surrounding rock is too broken, can use anchor agent to seal the hole.

3. Connect quick grouting coupling and anchor rod end, connect other end of grouting machine.

4. Start grouting, when grouting full and reach design value then power off . Grouting pressure according to the design parameters and grouting machine performance determine ,Cement/sand reference values is 1:0 ~ 1:1, water/cement reference value is 0.45:1 ~ 0.5:1.

5. Install anchor plate and nuts, and tighten nuts.

3. Both rope threads and trapezoid threads are robust and ideal for rotary-percussive drilling and ensuring a high level of bondwith the borehole gout.

4. The hollow core not only serves for flushing during drilling, but also for grouting after drilling.

1. No casings required, because anchor bars can be drilled into loose soils without needing casings to support the boreholes.

2. Fast drilling and installation, because drilling, installation and grouting are in a single operation.

5. Continuous threads ensure the bars can be cut and coupled at any point, or extended.

6. Different anchor bits are available for different ground conditions.

Applications of Self-Drilling Hollow Rock Bolts

1 Tunnel and Underground Project

In tunneling and underground projects, self-drilling hollow rock bolts play a crucial role in initial support and stabilization. These rock bolts provide high-
pressure grouting to fortify soil or rock masses, ensuring surface stability and structural integrity within tunnels. According to the types of support in the tunnels, self-drilling hollow rock bolt can be divided into fore piling, radial support, tunnel-face support, locking the foot support and reinforcement of the tunnel portal.

2 Ground and Foundation Project
 

For ground and foundation projects, self-drilling hollow rock bolts serve as versatile solutions for micro-piling and structural reinforcement. These rock
bolts effectively transfer pressure, tension, or periodic loads to the surrounding soil, limiting deformation and enhancing foundation stability. They can be used as new building pile foundation, existing building structure repair, tower foundation, bridge reinforcement, soundproof wall foundation, protective screen pile foundation, anti-floating pile foundation, retaining beam anchoring and other different structural scenes.

3 Slope Stabilization Project
 

In slope stabilization endeavors, self-drilling hollow rock bolts offer robust anchoring systems to mitigate geological hazards and prevent slope instability. Slope stabilization is ensured by the entire anchoring system itself subjected to tensile and shear forces. It can be used as soil nail support, slope protection barrier, falling rock protection, retaining wall, embankment stability, roadbed reinforcement and other different application scenarios.
 

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