Design & Construction Challenges of One the Deepest RCC Bored Cast-In-Situ Raker Pile-Paper

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The paper describes the design and construction of foundations for a 300 m, five-span railway bridge across Ghana’s Volta Lake. The lake’s deep water, highly variable riverbed geology, and uneven rock levels made the project unusually challenging. A revision to the Ghana Building Code increased the site’s peak ground acceleration from 0.16g to 0.35g, requiring a major redesign of the foundations to resist higher seismic forces.<br /><br />The original design used 2.0 m diameter vertical piles. Engineers adopted inclined (raker) piles, which use axial force to help resist horizontal loads, reducing the pile diameter to 1.6 m and lowering the overall pile demand. The longest pile reached 76.5 m, including its rock socket; piles were installed at a 1:5 rake.<br /><br />Construction took place from barges and required specially designed temporary platforms and guide frames to position and maintain the inclined liners. Reverse-circulation drilling, reinforcement-cage installation, and tremie concreting were carried out through the liners. Because actual rock levels often differed significantly from investigation estimates, the design team reviewed each pile group during construction and communicated any necessary adjustments before concreting.<br /><br />The team completed 30 pile foundations, and the bridge was finished in 2024. The project demonstrates how coordinated design and site monitoring, combined with purpose-built marine construction methods, can address seismic, geological, and logistical challenges in deep-water bridge foundations.

Keywords

Volta Lake bridge

railway bridge foundations

raker piles

deep-water construction

seismic redesign

Ghana Building Code

rock socket piles

marine piling

reverse-circulation drilling

pile foundation monitoring