Oldie but Goldie Deep Piles at Geneva with Base Enlargement, Tested Bi-Directionally with Osterberg Cells is a Smart and Economical Alternative to Conventional, Larger Piles-PPT Presentation

PPT Presentation

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The presentation describes the use of bored foundation piles with enlarged bases for an extension to the Rolex factories in Geneva, Switzerland. The project includes six above-ground stories and three basement levels, requiring excavation to 13 m within a site enclosed by a diaphragm wall extending to 48 m.<br /><br />Geneva’s ground conditions include thick, weak post-glacial deposits over competent moraine at approximately 30–35 m depth. The initial design used 41 cylindrical piles, 1,500 mm in diameter and about 50 m long, to reach the moraine. The alternative used 41 piles with 800 mm shafts and 1,850 mm enlarged bases seated in the moraine, reducing pile length by approximately 8 m.<br /><br />Construction involved drilling and casing the shaft, forming the base enlargement, installing reinforcement and a tremie pipe, concreting, and extracting the casing. Piles were tested using bidirectional load cells installed between the upper and lower reinforcement cage sections. The presentation notes that Swiss standard SIA 267 does not specifically regulate piles with base extensions; it also references European standard EN 1536:2015.<br /><br />The alternative design substantially reduced material quantities: excavation debris fell from 2,307 m³ to 726 m³, concrete from 2,416 m³ to 757 m³, and estimated material-related CO₂-equivalent emissions from 620 tonnes to 200 tonnes. The project presents enlarged-base piles, verified through bidirectional testing, as a more economical and resource-efficient foundation solution.

Keywords

bored foundation piles

enlarged base piles

Rolex factories Geneva

deep excavation

diaphragm wall

post-glacial deposits

moraine foundation

bidirectional load testing

EN 1536:2015

SIA 267