Monopile Penetration Through Scour Protection – Full Scale Testing and Discrete Element Analysis

There is no established methodology available in literature to assess the penetration resistance of (Mono)Piles through pre-laid scour protection, as concluded by Barbuntoiu (2021). Due to the lack of available literature, standard practices or industry guidelines on this topic, the authors performed in-house research on the subject. This paper deals with full scale testing performed to investigate the load-penetration behavior of armor rock. Tests comprised penetration of a steel pile section of a monopile into armor rock of two different gradings, placed on a sand bed in a 20 ft container. A DEM model with an equivalent setup was built and calibrated against the experimental test results and subsequently used to model a full size monopile case. Insight into the variability of penetration resistance was acquired by conducting multiple tests during the experimental and numerical modelling phases. Next to estimating self-weight penetration, knowing the penetration resistance over depth relation for a given scour protection layer provides an understanding of the penetration behavior of the pile at the transition zone between scour protection and seabed (i.e. potential for punch-through) and answers the question about necessity to use a piling hammer to penetrate the scour protection.