Dynamic Compaction of Rockfill on Land and under Water at Stockholm Norvik Port-Paper

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The paper describes dynamic compaction of coarse, boulder-rich rockfill for Stockholm Norvik Port, where conventional penetration testing was impractical and strict settlement limits applied. On land, a 20-tonne pounder was dropped from 20 m; underwater, the same compaction approach used a 10 m drop because of water-depth constraints.<br /><br />Trial areas were instrumented with inclinometers and extensometers to assess compaction depth, while accelerometers mounted on the pounder recorded its response at impact. On land, measurements indicated a maximum depth of influence of about 10 m, consistent with the Ménard empirical relationship. Accelerometer data were integrated to derive stress–displacement curves and estimate rockfill stiffness. Underwater, impact energy was estimated at about 12% of the on-land value, reflecting buoyancy and water drag. Applying this energy reduction to the empirical relationship suggested an underwater influence depth of roughly 3.5 m, though this estimate was not independently verified.<br /><br />The underwater stress–displacement measurements indicated a lower displacement modulus than on land. These results, together with estimates based on crater depths and density change, were used to predict settlements of approximately 0.05–0.1 m under loads from quay walls and additional fill. The authors emphasize uncertainty due to the rockfill’s variability and limitations in measurement and interpretation.<br /><br />The compaction works covered about 85,000 m² on land and 30,000 m² underwater. The study demonstrates the potential of accelerometer monitoring for evaluating dynamic compaction where standard testing is unsuitable, and highlights the need for further research to validate methods for estimating underwater compaction depth.

Keywords

dynamic compaction

rockfill

underwater compaction

settlement prediction

accelerometer monitoring

Stockholm Norvik Port

boulder-rich fill

Ménard relationship

stress-displacement curves

settlement limits