With structural obstacles in the launch shaft, and a road located directly above restricting access, maneuvering TBM parts into their final assembly position was proving problematic for Singapore-based contractor Yo Sin Engineering Work (YSE). In the face of such demanding site constraints, the company turned to a novel hydraulic slide solution.
Following an online search of available options, Canada-based Hydra-Slide was engaged at short notice to provide the technology needed to slide the machine parts of a 6.96m TBM some 20m beyond the lowering point and into position for assembly. The solution was required prior to launch of the machine on a critical 600m underwater section of a major subway project in the island state.
Having discovered Canada-based Hydra-Slide online, YSE was convinced that this was the right equipment for the job. Given the project’s extremely tight time constraints, the 10.5 tonne HT300 system was transported to the jobsite by cargo plane, then by truck, rather than by the usual method of sea transportation. Additionally, Ekki hardwood jacking timbers supplied by Hydra-Slide were also air freighted directly from the mill in Holland to Singapore.
Once set up of the slide system was completed, the components of the 461-tonne TBM were individually lowered down the 30m shaft by a Terex AC700 crane at ground level, and onto a Hydra-Slide HT300 hydraulically powered skidding system.
Robert Young, Director of Operations at Hydra-Slide, was present onsite to provide training for YSE personnel on the set-up and operation of the HT300 skidding system and to witness the first slide of the TBM components.
“This is actually the perfect application for the HT system due to its modular design, light weight and ease of assembly,” said Young. “No extra ground testing was necessary because the base of the launch shaft was poured concrete that was capable of supporting the weight of the HT300 and its loads. This was the first time our equipment has been used to move a TBM 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 scope of supply included provision of specially designed skid shoe extensions, which allowed the TBM’s base full contact support with the skid system.
Jefferson Yee, General Manager at YSE, explained that the front body assembly of the TBM consisted of six pieces weighing 241 tonne in total, all of which were lowered into the launch shaft and assembled directly on the HT300 skid system prior to being slid into place as a single assembled piece further down the shaft. This front section comprised the front shield bottom (34 tonne), the main bearing assembly (98 tonne), front shield top (32 tonne), cutterhead (64 tonne), plus the working deck and manlock which together added another 13 tonne of weight.
Yee explained that after the pre-assembled front body was pulled off the Hydra-Slide and onto the launch cradle – using hydraulic jacks – the middle body was then lowered in a single 128 tonne piece, followed by the 64 tonne rear body, and, finally, the two-part screw conveyor, weighing an additional 28 tonne. In this way the sub-assemblies were transferred to the launch cradle in manageable pieces, before being connected together.
“The project was a huge success,” said Yee. “I would like to thank the Hydra-Slide team for helping us achieve our goals for the installation of the TBM.” The subway project is scheduled for completion in 2018.