The Section Design of SDA Bolt

In the construction where the SDA bolt is used widely, the primary problems are to improve the drilling speed and reduce the cost of engineering. Therefore, it is an relatively ideal choice to adopt the minor diameter SDA bolt and high speed drilling. The rock drill commonly used can be required to applied flexibly.

Generally speaking, if the diameter of the SDA bolt hole is φ32mm, the corresponding diameter of the SDA bolt is φ24mm. According to the construction experience, the height of the loose area in the tunnel vault is about half of the support interval. In the Japanese construction, the support interval is about 1.2~1.5m, and the height of the loose area in the tunnel vault is about 0.6~0.8m. The SDA bolt must own the ability to support the loose load of 2~3t/㎡. One SDA bolt whose diameter is φ24mm can be predicted to own 20~22t ultimate supporting ability. Thus it can be seen the section design has owned enough safety.