Foundation Problems of a Cable Stayed High Bridge and Its Approaches

The Evripos crossing project (Greece) consisted of: The main cable stayed high bridge with three spans (90m- 215m- 90m), two approach bridges with four spans (36m and 39m) and two embankments on soft marine deposits. The pylons of the main bridge were founded on cast in situ R.C. piles, 120cm diameter, embedded in ophiolithic rock or cretaceous limestones, base and skin grouted. Limestone cavities were identified by continuous recording of the borehole drilling using the Enpasol technique. A fully instrumented pile was tested for vertical and lateral loading. For the foundation of the two end piers of the high bridge on limestone, micropiles in tension were used to resist the uplift forces. For the stability of the approach embankment in St. Stefanos Bay, on a 15.0m thick very soft to soft marine clay, ground improvement techniques were used, including excavation and replacement by rockfill of the surfacial (3.50m), very soft layer, installation of prefabricated vertical drains and preloading. The performance of the embankment was monitored during construction. Results and conclusions on the instrumentation are presented