Tunisia

Single level single cell installed in Tunisia The need to connect the ports of Rades and La Goulette by a land bridge was essential to promoting the development of both North and South Tunis lake areas as well as enabling expansion of the two ports. It was, therefore, necessary to construct a bridge as part of the metropolitan ring road crossing the Tunis Lake canal. The soft nature of the alluvial soils on this project required a unique testing solution to evaluate the parameters for the pile design. A top down test was considered which would require either anchor piles to lengths in excess of the test pile or heavy kentledge that may be unstable on the soft ground. The loads required would have proved very costly for these testing techniques. A sensible alternative was a bi-directional test in which a sacrificial jack (O-cell) is cast within the pile itself. This project is seen as the most important construction project that has been undertaken in Tunisia in modern times. At present the route between the ports is either by an ageing ferry for light vehicles or a long circuitous route for heavy traffic. The bridge will span 270 m over the canal at a height of 20 m.

The requirement for 16 MN total test capacity was the primary driving force in choosing bi-directional testing. One O-cell® of 540 mm diameter was installed 21 m above the tip of the pile in the 62m, 1500mm diameter test pile. It was assessed that large settlements could be present during the test and to accommodate these movements, an extended travel O-cell® with a 225 mm stroke was used. Conventional tell-tale arrangements were used to monitor the O-cell® expansion and pile toe movements. Strain gauges were placed at the pile toe to monitor the amount of load transferred to the base.

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Tunisia