Guinea Bissau, West Africa
To the North of Bissau several rivers have made road traffic to and from Senegal a challenge. The last remaining river to bridge is the Cacheu river and at São Vicente the existing ferry service will soon be replaced with a European funded road bridge some 50 kilometres from the capital city.
To confirm the foundation pile design in the soft sandy clays verification of the bearing capacity was sought by performing a static load test. Performing a top-down test (load applied to the head of the pile) to the magnitude of load required for each foundation element would have required mobilising a very costly reaction system and at least 4 anchor piles; as a more economic option, an O-cell bi-directional static load test was prescribed.
In order to test one of the deeper 1600 mm diameter piles and apply the maximum load required, one 670 mm diameter O-cell sandwiched between bearing plates was cast into the pile located approximately 10.5m above the toe of the 56 metre long bored pile on the South side of the river.
In addition to the standard instrumentation, LCPC (Laboratoire central des Ponts et Chaussées) employed a series of strings of removable extensometers arranged in nine segments for the pile above the O-cell and three levels below to determine the change in compression along the pile and deduce the distribution of skin friction.
A combined bi-directional loading mobilised over 22 MN in 16 loading steps resulting in displacements of approximately 7 mm upwards and 80 mm in the downwards, providing an excellent geotechnical interpretation of the behaviour of the end bearing performance using the Cemsolve® Method of analysis.
Project Profiles:
- Helsinki, Finland
- Guinea Bissau, West Africa
- Imperia, Italy
- Kiev, Ukraine
- Jeddah, Kingdom of Saudi Arabia
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