Zusammenfassung
Purpose: The utilization of dredged material in dike construction as a substitute for traditionally used aged marsh sediment is considered an advisable option with respect to ecological as well as economic aspects. As a prerequisite to the application, the equivalency with respect to soil physical and mechanical properties of the materials has to be verified. Previous investigations on the compactibility of dredged materials used for dike construction had shown that the bulk densities of these materials were considerably lower than bulk densities of aged marsh sediments. The aim of the investigations presented in this paper was to analyze whether the compactibility of the processed dredged material could be improved by enhanced dewatering of the material prior to construction. It was hypothesized that a decreased water content of the material would allow higher bulk densities to be achieved during construction and hence the soil physical properties would become more comparable to those of the aged marsh sediments.
Materials and methods: To examine whether the compactibility of dredged material can be enhanced by pre-drying, Proctor tests were carried out at different initial water contents. Moreover, it was examined whether the temperature of oven-drying at 30 and 105 °C affects the compactibility of these materials and whether ripening, i.e., the repeated drying and wetting of the dredged material under natural and laboratory conditions, can improve their compactibility.
Results and discussion: The investigations on the effect of the various further processing methods showed that the compactibility and therefore the suitability of processed dredged material for dike construction can be improved by air-drying. A linear relationship between dehydration and Proctor density was found. Air-drying to water contents of 10% dry weight (DW) resulted in an improvement of the Proctor density of up to 11%. However, the tests on the effect of the drying temperature on the compactibility showed that oven-drying had no additional effect on the compactibility of the dredged materials. Ripening under laboratory and natural conditions did not lead to statistically significant changes in the compactibility of the processed dredged material either.
Conclusions: Air-drying of processed dredged material to water contents less than 10% DW is considered to be a useful pre-treatment option to improve the compaction behavior of processed dredged material and to obtain a better functional equivalency with traditionally used dike construction materials such as fine-grained aged marsh sediments.
