Increase of bearing capacity of foundation soil in Port of Koper (Slovenia)

Abstract

The Port of Koper is situated in the northern part of Adriatic Sea and is the only maritime port for Slovenia to handle its seaborne cargoes. All port terminals and structures need high bearing capacity of foundation soil in the case of shallow foundations or require deep foundations for their construction elements, which is considerably more expensive. The entire Port of Koper was built on the area, acquired with dredging and reclaiming from the shallow sea bottom. Till 1969 the sea depth on this area was about 2m. It was reclaimed with dredged material from the sea bottom till level about +1m msl and after that the area was filled with moulded marl and crushed rock till level about +3m msl. From the soil investigation it can be seen that the soil layers consist of weak silty and clayey soils with low bearing capacity. For the shallow foundation the bearing capacity of the foundation soil has to be improved. To increase the bearing capacity and to accelerate the consolidation, gravel piles in a polymer meshes and preloading with the embankment have been installed at the site. During the consolidation process the ground water was filtered up because of preloading embankment, using gravel piles as vertical drainage system. The whole system was equipped with observation points for settlement observations and we were able to observe the soil consolidation degree. The results of settlement readings during preloading time on the site, were exceptional close to computational ones based on the theory of elasticity with mean modules of compressibility and to those based on the theory of finite elements.