Geotechnical investigations of sandy seafloors using dynamic penetrometers

Geotechnical in-situ characterization of the strength of the shallowest sub-seafloor sediment is an important factor in offshore engineering (e.g., scouring at wind energy plants), coastal engineering (e.g., sediment erosion close to the shores and beaches), navy applications (e.g., mine burial) and research (e.g., dunes in tide-affected areas). Dynamic penetrometers are well known as time- and cost-saving means to derive sediment physical properties in-situ and to detect layering or changes of strength of the shallow marine deposits. However, until now such instruments were rarely used on hard sandy seafloor because of their small penetration depth. The aim of this study is to unravel how applicable dynamic penetrometers are on sand and what kind of information they can deliver. Deceleration — depth signatures of the devices are used to compute quasi-static bearing capacity and related to governing parameters such as mineralogical composition, grain size distribution and sedimentary layering.