Sinorock R51 Self-drilling Rock Bolt in Tunnel Roof Support

The Zhengwan high-speed railway is 818 kilometers long, connecting Zhengzhou, Henan and Wanzhou, Chongqing. It is an important part of the Beijing-Kunming corridor in my country's eight-horizontal and eight-vertical high-speed railway network, and it is also a newly planned railway included in the national "Twelfth Five-Year Plan" period. Construction started at the end of 2014 and is expected to open to traffic in 2022.

The Gaojiaping Tunnel of the ZWZQ-5 bid section of the Hubei section of the Zhengwan High-speed Railway has complex engineering geology, difficult construction and high safety risks. The inlet section is V-grade surrounding rock, mainly composed of medium-strong weathered shale, weak surrounding rock and high water-rich karst cave, broken rock mass and poor self-stability, and the lining type is Vcw composite lining. During the construction process of China Railway 11th Bureau, Sinorock R51 self-drilling bolts were used as advanced pipe shed support, instead of traditional steel pipe sheds.

There are 50 holes per ring at the top of the end face. The hole spacing is 400mm, and the hole depth is 25 meters. The hole is inclined upward at an angle of 7°. When drilling, we use R51/76 tungsten carbide button drill bit, and the hole diameter is 76mm. After the drilling is completed, the grouting shall be carried out. The water-cement ratio of the cement slurry is 1:1, and the grouting pressure is 0.5-2.0MPa. After the grouting is completed, the orifice shall be blocked with a grouting plug.

It has been verified by the practice of the Gaojiaping Tunnel that the self-drilling hollow bolt is safer and more efficient than the traditional pipe shed for drilling and installation under this geological condition.