Advantages of self drilling hollow anchor bolts used as soil nails

Soil nailing is currently an important technology for reinforce slopes such as mountains, dams and building foundations. However, the traditional technology is to drill holes first, and then anchor bars are embedded in the holes and grouted and fixed. The construction process not only faces problems of high construction difficulty, low work efficiency, and high cost, but also faces the problem of poor connection stability between soil nails and geological structures. In recent years, self drilling hollow anchor bolts have been widely used in soil nail support due to their simple construction technology and good anchoring effect. Today I will introduce the advantages of hollow soil nails.
What’s self drilling hollow anchor bolts?
Self drilling hollow anchor bolts are composed of hollow anchor bar, nut, plate, coupler, centralizer and drill bit. It can combine drilling, grouting and anchoring functions together. Without using casing pipe, it can greatly improve the construction efficiency and shorten the construction cost.
Construction process
1. Preparation work. Check whether the functions of drilling rig are normal, whether the drill bit and anchor rod are damaged, and whether the rod body is unblocked, etc. After making sure that there is no problem, screw the hollow anchor bar to the drill bit.
2. Drill and grout. Connect anchor rod and grouting pipe to the drilling rig through a rotary grouting adapter, and simultaneously drilling and grouting.
3. Coupler anchor rod. If a single anchor rod can’t reach the designed drilling depth, a coupler can be used to meet the design requirements.
4. Installation the plate and nut. After grouting, install plate and nut close to the construction surface to ensure the anchoring effect.
5. Field test. After the installation is completed, the self drilling anchor rod is tested for its pull out force to check whether it meets the design requirements.
Traditional soil nail is installing solid steel bars into pre-drilled holes and then grouted and anchored. Compared to traditional soil nails, What are the advantages of self drilling hollow soil nails?
1. In loose or easily collapsed geological conditions, no casing is needed. Therefore, when installing soil nails, most of the drilling rigs are small and can well cope with slopes and narrow spaces.
2. Simultaneous drilling and grouting process can increase the grout body diameter and maximize the shear force of grout body/soil interface.
3. Simultaneous drilling and grouting process is less vibrating, which effectively reduces the interference to the surrounding soil.
4. The installation speed of hollow soil nails is twice that of solid soil nails thanks to the construction technology.
5. Can replace concrete retaining wall.
6. High-pressure grouting process can inject the cement grout into the loose stratum, greatly increasing the grout diameter and its friction force, and the anchoring quality is better than that of solid soil nails.
Through the introduction, we know that self drilling hollow anchor bolts used as soil nail is an efficient and economical ground support method, which can control and improve the soil natural stability.

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