Background of the Project

The project is located between Yuanjiang County and Mojiang County, Pu'er City, Yunnan Province. It is a double-track tunnel with a total length of 17476m. The Anding Tunnel is located between Nanxi River and Mojiang Station. It is a double-track passenger and cargo tunnel with a design speed of 160km/h. The line starts from the middle mountainous area of ​​Ailao Mountain, which belongs to the middle and low mountain landforms of tectonic denudation. Due to tectonic denudation, the terrain is undulating, the surface valleys are vertical and horizontal, and the structure is very developed, partly covered by steep slopes. The vegetation on the slope is developed, mostly covered by shrubs and pine trees, and there are a few villages near the cave body. The maximum buried depth of the tunnel body is about 880m, and the minimum buried depth is 20m.


Project Overview

Project duration:	October 2018 - September 2020
Scope of services:	Anchoring materials and on-site technical services
Application scenario:	Self-drilling advanced pipe shed in the railway tunnel
Application structure:	Self-drilling hollow bolt is used as support for an advanced pipe shed
Project consumption:	About 5700m
Geological conditions:	The grade of the surrounding rock of the tunnel is grade III-V, of which the section being excavated is grade Vc. The surrounding rock is mostly the intersection of the fractured zone and the fully weathered zone. Most are muddy fillings.

Questions and Challenges

Ordinary pipe sheds are difficult to drill under the special surrounding rock conditions with many soils and weathered rocks, the construction efficiency is low, and the tunnel excavation speed is slow. The geological conditions of the project are poor, and the rock is V-grade rock, which is easy to collapse, and there is a problem of hole collapse and stuck drilling.


Solution

The tunnel reserves the core soil method for annular excavation and self-drilling rock bolts are used as advanced pipe sheds for temporary support during tunnel excavation to protect the safety of construction personnel and equipment. After the tunnel excavation is completed, install the steel arch frame, hang the steel mesh, and spray cement slurry to complete the main construction of the tunnel. The pipe shed remains in the rock mass and still plays a supporting role.


There are 47 drill holes in each ring, and 18/15 meters of pipe shed drill holes are arranged alternately (3*6m, 2*6+3m long hollow bolt).

Construction Technology

Construction Preparation→Measure And Stakeout→Rig In Place→Install Shank Socket→Connect Soil Nail→Install Drill Bit→Drilling→Remove the Shank→Lengthen the Anchor Rod and Connecting Sleeve→Continue Drilling→Circularly Extend the Anchor Rod Until the Design Depth →Remove the Shank Sleeve→Close the Nozzle→Install the Grouting Joint→Connect The Grouting Pipe→Complete the Grouting

Construction Equipment

Drilling rig: The drilling rig is the Tiejian Heavy Industry three-arm rock drilling rig ZYS113, the Montebay power head, and the shank specification T38.

Construction efficiency: The average drilling time of a single hole (21m hole depth) is 40min, and the drilling time of 17 holes per ring is about 11h.


Project Test

The tunnel is the longest tunnel on the Yumo Railway, and the geological conditions are extremely complex. The self-drilling rock bolt is used to overcome difficulties such as collapsed holes and stuck drilling. The drilling and installation effects are good, and the drilling speed is fast. The project has been successfully completed by the end of 2020.