Rectangular TBM for urban underpasses 18 May 2017

An innovative box-jacking rectangular TBM (RTBM) has completed a 150m long trenchless pedestrian underpass at the Havelock Metro Station in Singapore. The 7.6m × 5.6m RTBM, designed and manufactured by CREG, utilised 20% more space than a circular TBM alternative making it ideal for excavating short-distance tunnels for urban underpasses and subway entrances and exits at shallow depths.

Breakthrough at Chengdu, Sichuan

This new method of construction improved manpower productivity by about 30%. Application of the technique for a first time in Singapore was helped by close cooperation between the project client, the Singapore Land Transport Authority (LTA), the main contractor Gammon Construction and the specialist sub-contractor China Railway Tunnel Group (CRTG).

In 2013, CREG developed and manufactured two RTBMs (10.12 × 7.27m and 7.52 × 5.42m) to excavate motorways and sidewalks for the Zhengzhou Zhongzhou Avenue undercrossing tunnel project in Henan Sheng, China. The two machines completed the four tunnels in late 2014. Unlike conventional cut-and-cover construction methods, where surface interventions are often required, the use of an RTBM resulted in a simpler and safer construction environment, with minimal noise and dust generation, which was a requirement in the project location in a densely populated area. The successful use of the RTBM sparked interest from government agencies and professionals both at home and abroad, and led to the LTA ordering an RTBM for the Havelock Metro Station pedestrian corridor. The TBM manufacturing company is now working on a trenchless method of building metro stations.

Last summer a CREG RTBM broke through in Chengdu, Sichuan, where it was the first to tunnel through cobble sand and at a depth of only 3.1m below the Chengdu Metro Line 1. Between the ground and the tunnel are 15 municipal pipelines, the nearest being only 0.5m away from the underpass. During construction there had to be continuous surface traffic, no damage to municipal pipelines and minimum disturbance to the metro line overhead.

At a seminar in Singapore last year (2016), delegates were offered insights into new rectangular TBM tunnelling technique. Highlights included an address by Henry Foo Yung Thye, Project Director of the Singapore Thomson East Coast-Line, who spoke of the benefits of the concept and the experience of using the rectangular TBM at Havelock Station. At the same conference, the new technology application was awarded Project of the Year in the Engineering & Construction Category.

Overwhelming growth of cities in developing countries is creating a strong demand for new underground infrastructure and underground space is an important potential resource. The RTBM developed by CREG is proving a useful tool for urban underpasses, underground expressways and ramps, utility tunnels and parking lots. The company continues to provide innovative solutions to address the problems of urban sprawl, traffic congestion and pollution.