Pile Foundation for Cable Support Structure in Brownfield Site with Underground Obstructions

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This case study describes the redesign of a cable-support tower foundation at an operating process plant in a restricted brownfield site. The tower had to remain in its planned location because the cable bridge was already fabricated, alternative locations would disrupt plant operations, and the adjacent road had to stay open.<br /><br />The original shallow raft foundation was replaced with a pile foundation after site investigations identified numerous live underground cables and a water pipe within the foundation area. Further trial excavation revealed additional cables that made the proposed pile arrangement unsafe and impractical. The utilities could not be shut down, moved, or disturbed.<br /><br />The final solution adapted the design to the safe pile locations identified at the site. Two separate pile caps, each supported by three 600 mm diameter, 12 m long bored piles socketed into rock, were connected structurally through a rigid steel portal. The existing tower was modified to bear on this portal. Analysis confirmed that the piles could safely resist the calculated compression, tension, and lateral loads, while portal deflection remained within the settlement allowance.<br /><br />The redesign enabled construction without damaging live utilities, relocating the tower, or closing the road, while maintaining safe plant operations. The case highlights the need for comprehensive underground as well as surface surveys during brownfield planning. Incomplete information about buried services led to repeated design changes, delays, and inefficient use of resources; early, detailed utility mapping and close coordination between design and site teams could have reduced these impacts.

Keywords

cable-support tower

foundation redesign

brownfield site

pile foundation

live underground utilities

bored piles

rock socketed piles

rigid steel portal

process plant

utility mapping