The Case of a Building Design Review Requiring a Full Foundation Redesign-Paper

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A review of a proposed nine-storey hotel with a basement in Accra revealed serious problems across the architectural, structural, geotechnical, mechanical and electrical designs. Structural elements were inadequately designed, and the proposed foundation did not address weak, collapsible soils and high groundwater. The confined site, bordered by existing buildings, also made basement excavation hazardous: slope-stability analysis found a factor of safety as low as 0.391, far below acceptable levels.<br /><br />The original proposal for a basement raft was abandoned. A shallow raft without a basement was also considered impractical because it would require extensive ground improvement. Micropiles were judged uneconomical, so the team selected a piled raft supported by bored concrete piles.<br /><br />Further investigation uncovered major discrepancies in the original geotechnical report. While it indicated increasingly dense ground below about 8 m, confirmatory boreholes found medium-dense silty sand at that depth. A third witnessed borehole confirmed the revised findings, prompting the team to redesign the piles to reach stronger ground. The final design used 103 bored piles, each 600 mm in diameter and 17.5 m long, with a 1 m-deep pile cap. Axial and lateral pile behaviour was analysed and incorporated into a structure–pile–soil interaction model.<br /><br />The case highlights the need to verify third-party geotechnical data when results are doubtful, thoroughly review all design disciplines, and maintain open discussions among project stakeholders—particularly when safety and costs are affected. The authors warn that inaccurate or unethical engineering practice can lead to unsafe foundations and excessive settlement.

Keywords

hotel design

geotechnical investigation

piled raft foundation

bored concrete piles

weak soils

groundwater

basement excavation

slope stability

structural design review

foundation safety