Self-drilling anchor bolts replace small conduits for tunnel support

The Hangzhou-Ruili Expressway, which was constructed by the China Railway 17th Bureau, passed through the Jigongshan Tunnel. This tunnel is located in Nayong County, Guizhou Province. The sea wave in the site is 1725.8~2214.7 meters, the maximum height is 488.9 meters, and the maximum depth of the tunnel is 420 meters. It is a type of Karst Landform with multiple chasms and complex geology.

The surrounding rock of the Jigongshan Tunnel is level III, which cannot guarantee the personnel safety during construction. The surrounding rock broke, the amount of water inrush was large, and holes were not formed when drilling. These problems were not able to be solved by using small conduits. After research, The construction party decided to use self-drilling rock bolts to replace the small conduit for support. Self-drilling hollow anchor bolts can combine drilling, grouting, and anchoring functions, which can guarantee the anchoring effect in the complex stratum, especially in the fault zone. It overcomes the difficulties of small conduits such as collapse holes, unable to insert bars, dissatisfaction with grouting. It is reliable, efficient, and convenient.

Compared with small conduits, self-drilling anchor bolts have the following advantages in construction:
  1. Self-drilling anchor bolts are made of good seamless steel pipe materials. The anchor bar and drill bar are combined into one, which improves the anchoring efficiency without casing pipe, and thus shortens the construction period.
  2. High-efficiency grouting can not only fill cracks, consolidate rock mass, and soil layer, but also ensure reliable anchoring quality.
  3. A drill bit with strong penetrating power is installed in front of the hollow bar. According to different construction geology, different materials are selected to ensure the drilling efficiency. Besides, the drill bit can stay in the hole after drilling, so that keep the anchor bolts centered and form a uniform protective layer.
  4. The hole collar plug makes the grouting pressure higher. The domed plate and nut can evenly transmit the stress to the rock, which achieves mutual support of surrounding rock and anchor bolts.
The use of self-drilling anchor bolts provided a safety guarantee for project construction and saved 25% of the workload, which laid the foundation for the early opening of the Jigongshan Tunnel. Self-drilling anchors are mainly used for the support construction of fault fracture zones, ensuring the overall stability of the surrounding rock. Sinorock has been insisting on the research and production of self-drilling anchor bolts for more than ten years, and the products have been widely used in tunnel construction. Sinorock focuses on solving the problems in anchoring construction projects and providing competitive solutions for customers.

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