Low-Vibration Installation of Ductile Iron Piles for Operation of a Power Plant
The municipal power provider
St. Lucia Electricity Services (LUCELEC)
expanded its power plant on the island of
St. Lucia in the West Indies. Due to difficult
geological conditions, the construction of the
building that was needed for the new
generator posed a special challenge.
The building ground was situated close to sea
level and founded on fill and alluvial material with
boulders over highly weathered bedrock.
The pile system did not only have to be suitable for the strongly varying substrate, but also for confined space and limited access on site. As the new foundation pilings needed to be driven within a mere 400mm of a working generator, vibration and noise had to be kept to a minimum. The x 170mm DYWIDAG Ductile Iron Piles supplied by DSI USA proved to be the perfect solution for this special case. During the piling operation, vibrations of only 2mm/s were recorded, which was well below the allowable British standard (BS5228) of up to 30mm/s for commercial buildings. In total, 72 ductile iron piles with a minimum length of 4m and a maximum length of 23m were driven to an average depth of 16m. Two test piles were subsequently loaded to 716kN using a hydraulic tensioning jack that was supplied by DSI. Loads were simply transferred to the reaction beams using bars consisting of DYWIDAG THREADBAR® that were set into the wet mortar after driving the piles. The piles passed the tests without any difficulties. The grouted annulus piles were very effective in overcoming the varied ground conditions. In addition, the piling rig could be moved to the different installation locations easily and quickly so that a flexible and very fast reaction to the different ground conditions that were encountered was possible.