The extensive modification project of the Hung Hom Station and the Hung Hom Coliseum area included an upgrade of the drainage system underneath the coliseum for which sheet pile sections had to be driven. This critical contract was executed without disruption to the existing Hung Hom station and in very low headroom. Piling was awarded to Grand Connection Consultants Engineering Limited who carried the job out using excavator mounted vibratory hammers and special low-headroom truck hoists cranes.
 
The sheet piling job consisted of driving 12 to 15m long No. 4 Larssen sheet piles. As there was only 6.5m headroom available the sheet piles were made up of 4m long sections that were welded together after driving. The first sections were driven by excavator mounted hammer but as the hammer met refusal at the last few meters from the compacted soil underneath the structures (originally completed in 1983) the client looked for a more powerful hammer. The client brought in the 416L first to add a higher eccentric force to the pile but the self-weight of the hammer wasn’t sufficient to drive the pile down and the 416L was exchanged for an 815C which did the job satisfactorily.

Because of the limited head space the only available option to lift the hammer onto the pile was by truck hoist. The start-up and shut down vibrations could easily damage the hoist’s mechanism and cause a safety incident. In consultation with an expert from ICE the hoist was used to position the hammer on the pile the hammer was only started after it was hydraulically clamped onto the pile. The 815C had sufficient amplitude and self-weight to drive the piles to design depth. ICE hammers are designed with very narrow throat width allowing even the larger hammers such as the 815C to go in between the piles. The 815C is powered by an ICE 600 power pack.