Pre-support with Pipe Umbrella System for Gaojiaping Tunnel

Time:2022-08-04View:

Introduction

The Zhengzhou-Wanzhou High-Speed Railway Project is a major project and an important part of the modernization of China's transportation infrastructure. The implementation of the project not only demonstrates the Chinese government's commitment and investment in infrastructure development, but also showcases the strength and technical proficiency of the Chinese engineering community.
However, during the construction of the Zhengzhou-Wanzhou High-Speed Railway project, numerous technical and engineering challenges were faced, one of which was the construction of the Gaojiaping Tunnel. Nevertheless, these challenges were ultimately overcome, resulting in a compelling success story. In this success story, Sinorock's innovative solution - the use of self-drilling anchor systems - played an important role in providing key technical support for the smooth construction of the tunnel.

pre-support with pipe umbrella system

Project Background

The Zhengzhou-Wanzhou high-speed railway spans a vast 818 kilometers, a massive endeavor with an estimated investment of CNY 118 billion. Upon completion, it promises to reduce travel time between Zhengzhou and Chongqing to under 4 hours, revolutionizing transportation in the region.

The Gaojiaping Tunnel

The Gaojiaping Tunnel, a part of the Zhengzhou-Wanzhou high-speed railway, is situated in the Hubei section, within Xiangyang City. The center mileage is DK451+786, and starting and ending mileage is DK449+037~DK454+535. With a length of 5498m and a maximum buried depth of 320m, it presented a significant engineering challenge. TThe tunnel adopts two-way tunneling at the entrance and exit, and the geological conditions were complex, featuring Grade-V surrounding rocks, moderately weathered shale, soft rock, and a lack of self-stability. The Gaojiaping Tunnel was surrounded by fragile conditions, demanding innovative engineering solutions to proceed effectively.

pipe-umbrella-system

Challenges

The initial design for the tunnel involved using steel flower pipes as pipe-roofing. However, complications arose during construction due to challenging geological conditions. This complexity was further heightened by the tunnel's ridge-crossing nature, where overlying soil was thin, bedrock partially exposed, and the surface primarily cultivated as dry land. In areas of broken rock, drilling became nearly impossible, bringing the project to a standstill.

Sinorock's Innovative Solution

To overcome the drilling challenges, Sinorock proposed the use of R51 self-drilling anchor bars. These self-drilling anchor bars, equipped with ESF R51/76 drill bits, were implemented at a drilling depth of 25m in a 4*5+3m arrangement. The system consisted of hollow anchor bars, couplers, and drill bits. Grouting after drilling secured an anchoring effect, and the anchor bar also served as a drill rod and reinforcement, significantly enhancing the construction process.

pipe-umbrella-work-principle

Construction Process and Equipment

Drilling Rig: ZYS113 three-boom drilling jumbo
Materials prepared → Survey lofting→ Drilling jumbo in place → Connect hollow anchor bar and drill bit → Percussive rotary drilling→ Couple next anchor bar → Repeated drilling and grouting → Drilling completion → Grouting →Enter into next circle → Installation completion
The process demonstrated high efficiency, with a net drilling time of about 1m per minute.

Project Overview

Project Duration	August 2017 – December 2017
Service Scope	Anchoring materials and on-site technical services
Application	Pre-support with pipe-roofing for railway tunnel
Application Structure	Self-drilling anchor bars used as pipe-roofing
Quantity Consumption	About 5000m
Geological Conditions	Grade-V surrounding rocks in some locations are mainly moderately weathered shale, with soft rock, broken rock mass, and poor self-stability. The lining type is Vcw composite lining. As a ridge-crossing tunnel, the overlying soil on the slope is thin, the bedrock is partially exposed, and the surface is mostly cultivated as dry land.

Conclusion

The success of the Gaojiaping Tunnel's construction demonstrates the ingenuity of Sinorock's self-drilling anchor system. It not only overcame the geological challenges but also enhanced safety and efficiency in tunnel construction. As China's infrastructure projects continue to push boundaries, Sinorock's commitment to professionalism and reliable products ensures a safer and more efficient future.
Sinorock's dedication to excellence translates into safer, more efficient, and cost-effective construction processes. If you have any needs or questions in the field of geotechnical anchoring, please feel free to contact us at sinorock@sinorockco.com.

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