Investigation of the properties of dredged limestone fill

Dredged limestone from the Øresund fixed link has been used for reclamation purposes and Peberholm and Kastrup. The IGG study - carried out partly as a Mid-term project for two student - utilises a number of geophysical and geotechnical investigation techniques, supplemented by laboratory testing. At the Kastrup reclamation site DSB is developing a maintenance centre. The Danish Geotechnical Institute has carried out geotechnical investigations and studied the fill properties using dynamic compaction and plate loading test. The resistivity contouring by IGG showed local variability in the 5 m thick fill layer which was confirmed by electrical soundings but not seen in the boreholes. The surface wave technique was able effectively to characterise deformation properties of the coarse granular material (dmax=200mm). It was concluded that the limestone fill could be divided in three main categories: (1) coarse well graded granular material with low fines content having good engineering properties when compacted, (2) loose layered silty fine sand prone to liquefaction, (3) very soft normally consolidated clayey silt with very low shear strength. The forward modelling of the continuous surface wave method was applied and the results compared very well with the plate loading test taking into account that SASW works at very small strain. The study showed that geophysical methods were applicable and very cost effective to more traditional geotechnical methods.