Yu Sin personnel lowering and bolting together the tunnel boring machine front body in preparation f

Yu Sin personnel lowering and bolting together the tunnel boring machine front body in preparation for a slide

Tunnel boring specialist Yu Sing Engineering Work, based in Singapore, skidded a tunnel boring machine using a Hydra-Slide HT300 during a major subway infrastructure project in Singapore.

The components of the tunnel borer were lowered down the 30 metre shaft onto a Hydra-Slide HT300 hydraulically powered skidding system by the Terex all terrain AC700 crane at ground level. When completed, the fully assembled tunnel boring machine will be 6.96 m in diameter and weigh 461 tonnes in total. The new subway tunnel will be almost 600 m in length, connecting two areas of the city currently separated by water, the company said.

Yu Sin sought a solution to move the boring machine parts over a distance of approximately 20 m and connect them in the launch shaft. The machine could not be lowered directly onto its working path because of a major road over the tunnel entry point and other structural interferences.

Given the project time constraints, the 10,500 kilogram HT300 system travelled by cargo plane and then by truck to the jobsite - shipments of this kind would more commonly travel by ocean with a transit time of about 45 days, the company explained. In addition, Ekki hardwood jacking timbers supplied by Hydra-Slide were also air freighted directly from the mill in Holland to Singapore.

Robert Young, director of operations at Hydra-Slide, was onsite to provide training for Yu Sin personnel on the set-up and operation of the HT300 skidding system.

He said, “This is actually the perfect application for the HT system due to its modular design, light weight and ease of assembly. No extra ground testing was necessary as the bottom of the launch shaft was poured concrete that was capable of supporting the weight of the HT300 and loads. This was the first time our equipment was used to move a TBM [tunnel boring machine] and we see future potential in this area, especially after the success of this project.”

In addition to the standard HT300 skid system, Hydra-Slide’s supplied specially designed skid shoe extensions, which allowed the boring machine’s base full contact support with the skid system.

Jefferson Yee, general manager at Yu Sin, said the front body assembly consisted of six pieces weighing 241 tonnes in total, which were lowered into the launch shaft and assembled on the HT300 skid system. It comprised the front body bottom (34 tonnes), bearing (98 tonnes), front body top (32 tonnes), cutter head (64 tonnes), working deck and man lock, which together added another 13 tonnes of weight.

After the front body was slid into place, the middle body was lowered in one 128 tonne piece, followed by the 64 tonne rear body and, finally, the two part screw conveyor that weighed 28 tonnes. At the end of each slide, the sub -assemblies were pulled onto the launch cradle using hydraulic jacks and connected together.

The project is scheduled for completion in 2018.

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