CHINA - DALIANGSHAN NO 1 HIGHWAY TUNNEL | PROJECT
journey to site on purpose-built tracks and through the snow and rain of a winter season. After 30 days in assembly, the machine was launched in October 2020, commencing its drive at the face of a 110m-long drill & blast starter tunnel.
ADVANCING KNOWLEDGE The application of a TBM to an expressway tunnel project will fill a gap for the industry. There is a network of 200,000km of expressway in China, with 26,000km of that running through 25,000 tunnels, most of these, other than those under rivers, excavated as open-face, NATM-type, drill & blast constructions. TBMs have been used on several long railway tunnels
in China but application for express highway tunnels through mountains is something new. The experience of a TBM pilot tunnel of the Daliangshan No 1 Highway Tunnel project has proven the many benefits of such an investment. During pilot excavation, however, the same geological
risks had to be anticipated, including high volume water ingress, squeezing ground, karstic voids, and fault zones of poor ground conditions. As a priority project, many research studies were
supported on the TBM pilot tunnel including: ● Seismic predictions of geological features ahead of the face;
● Design of support parameters for different rock classifications;
● Support in soft rock with arches and straps; ● Forepoling in soft rock; ● Support using shotcrete and bolts in combination; ● Muck analysis and use as a valuable resource rather than a waste product;
● Design of gauge cutters to compensate for convergence;
● Scanning of supported headings to check deformation, and to check the same through the secondary lining once installed; and,
● Application of robots for installing arches as part of a national research project to reduce labour on tunnelling projects and increase safety.
As a benchmark in expressway tunnelling, the pilot tunnel has given rise to: 50 academic papers; development of 10 new technologies; formed the basis of 10 new codes of practice; and, 30 new patent applications have been filed. Other expressway projects in Sichuan, and in China, will make use of the lessons learned on this pilot project. Participating in the important research project, the
China Railway Academy (CRA) of Chengdu, Sichuan, was engaged to carry out specific studies associated with the TBM pilot drive. These included: ● Application of the CRA HSP Geological Prediction Systems to help predict conditions ahead of the face without stopping the TBM;
● Confirming rock class definitions and their support requirements;
● Study of the ventilation benefits of the pilot tunnel both during excavation of the two main tubes and in operation of the expressway tunnel once opened; and, ● Advance the study of construction cost unit prices.
For predicting conditions ahead of the face, CRA used its HSP217T on-board prediction system that uses the vibration of the TBM cutterhead, as it cuts the rock, as the excitation source. These vibrations are detected in
Above: Example of an HSP217T test readout predicting conditions ahead of the TBM pilot drive September 2024 | 33
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