TBM u-turn within an hour 21 Dec 2017

After two days of planning and preparation, it took one hour to turn a TBM at the end of its first drive into the headwall of its parallel drive.

TBM turned in its entirety

The turning system supplied by Hydra-Slide comprised the combination of a HT300 heavy track hydraulic skidding system and the TT900-10 engineered turntable. After breaking through after its first drive, the 6.7m diameter, 520 tonne Hitachi Zosen TBM was slid 12m onto the Hydra-Slide turntable using the HT300 hydraulic skid system with four rails and four push cylinders applied to increase the overall HT300 push capacity.

Once on the turntable, the machine was rotated through 180 degrees to complete the second drive for contractor Yu Sin Engineering on its landmark Gardens By The Bay station and tunnels contract for the Singapore MRT Thomson-East Coast Line.

“Initially the plan was to dismantle the TBM at the end of its initial 679m tunnel and return and re-launch it at the working shaft, but this would have taken a long time and we wanted to explore the option of a u-turn,” said Jefferson Yee, General Manager for Yu Sin Engineering. “After consulting with Hydra-Slide on the technical possibilities we proceeded with the alternative option which resulted in significant and important time savings.”

The HT300 and TT900 in position prior to the slide and rotate

The HT300 and TT900 units were used during the initial assembly of the machine and at other stages of the project and were used in combination to move and rotate the TBM in its entirety, 30m underground. Standard track lengths of the HT system are 3m and 6m but Hydra-Slide can customize track lengths to suit almost any requirement. The tracks are connected by a simple lug and pin set and can be leap-frogged to slide longer distances.

The HT300 remained in place while the rotation was completed in one continuous motion, with the turntable plus cylinders automatically resetting into ratchets after each push. The TT900, which had already been lowered into the shaft using a 250 ton capacity crawler crane, is more commonly used to turn transformers or generators during handling or installation, but it is suited to rotation of any heavy or oversized loads. The crews in Singapore, reported Yee, said that the turntable demonstrated versatility and reliability.

“We were familiar with the HT300 after the first sliding operation, but the TT900 proved to be just as fast, safe and easy to operate,” said Yee.

6.7m Hitachi Zosen TBM weighs 520 tonne

Aerial view into the 30m deep working shaft

“It is a simple system to operate,” explained Janine Smith, Vice President at Hydra-Slide. 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 product turntable. To the best of our knowledge, it is the first time the turntable has been used underground on a tunneling project; Yu Sin pioneered utilization of the equipment to exploit the cost savings and increased efficiency for future TBM projects.”

The HT300 skid system and TT900 turntable in combination is a cost-effective, accurate and safe method for moving, loading, unloading or rotating all types of heavy loads. Engineered ratchet track designs enable continuous movement and automatic resetting of push cylinders without personnel being nearby during a move. The HT300 is 180mm high and the TT900 is 150mm high. This saves jacking time and is ideal for working in confined spaces.