Rotating a TBM

Singapore-based tunnel boring specialist, Yu Sin Engineering Work Pte Ltd, has rotated a tunnel-boring machine (TBM) at a major subway infrastructure project in Singapore. The site is part of the landmark Gardens by the Bay MRT station project, a planned underground Mass Rapid Transit station on the Thomson-East Coast Line in Marina South.

The TBM, manufactured by Hitachi Zosen Corporation, measured 22ft. (6.7m) in diameter and weighed 570 tons (520 tonnes). It had completed an initial 2,225ft (679m) tunnel and had to be repositioned to start its next boring assignment.

To move and rotate the TBM in its entirety, 100 ft. (30m) underground, Yu Sin Engineering Work used a Hydra-Slide HT300 Heavy Track hydraulic skidding system and a TT900-10 engineered turntable. After two days of pre-planning, the actual rotation was completed in just one hour by skidding it onto the turntable, jacking down and rotating 180 degrees.

Prior to the rotation, the HT300 slid the TBM 40 ft. (12m) using four rails and four push cylinders to increase the HT300’s overall capacity. The HT300 remained in place while the rotation was completed in one continuous motion, with the turntable pus cylinders automatically resetting into ratchets after each push. The TT900 had already been lowered into the shaft using a 250 ton (227 tonne) capacity crawler crane.

According to Jefferson Yee, general manager, Yu Sin Engineering Work, said, “Initially the plan was to dismantle and relaunch [the TBM] but this would have taken a long time and we wanted to explore the option of a U-turn. After consulting with Hydra-Slide on the technical possibilities we proceeded with the alternative option, which resulted in a huge time savings.”

The TT900-10 turntable, ordered by Yu Sin earlier in 2017, is a modification of Hydra-Slide’s TT500-10, designed to accommodate extra cylinders and rotating force. It was shipped to Singapore in an open-top container via sea freight. Janine Smith, vice president at Hydra-Slide said, “It is a simple system to operate. We have designed our turntables with the same safety principles as our skidding systems – there are no winch lines or holdbacks required, the push cylinders automatically reset into specially designed ratchets on the side of the turntable, and there is no manual handling of any components required during operation. We spoke with the crew in Singapore when a question arose but they did not require any training on the turntable. To the best of our knowledge, it is the first time the turntable has been used underground on a tunnelling project; Yu Sin should be applauded for their pioneering utilisation of the equipment. We see our equipment providing great potential for cost savings and increased efficiency in future TBM projects.”

The tunnel boring is scheduled to complete by end of 2017.