Harbour Maintenance Dredging Operations – Residual Characteristics after Treatment by Means of Geosynthetic Dewatering Tubes
In order to increase the knowledge and understanding of the geosynthetic dewatering tube system the two first harbour maintenance projects executed in Germany, Verden (Wilke, 2011) and Husum, where the dewatering tubes have been applied, were scientifically supervised by the University of Rostock. The smaller project in Verden was executed in 2010 and was dealing with the remediation of approximately 1000 m³ of harbor sediment. The other project in Husum, executed in 2013 and 2014, was split into two phases: one trial section with 6,000 m³ in 2013 and the follow-up section of in total 50,000 m³. One main focus of the scientific analysis consisted in the time related achievable dry solid content after pumping the conditioned sediments into the tubes. This topic has been analyzed in detail. Moreover some other basic analysis (e.g. sieve curve analysis, loss of combustion, densities, calcium content, etc.) have been performed. As the tubes can be installed in a stacked pyramidal pattern with several tube layers another question raised was the undrained shear strength of the dewatered material. By using a hand-held vane tester the undrained shear strength at several locations in different tube layers was determined.