Presently, there are no standardized methods for modelling the installation of monopiles. Companies typically use published research based on jacket piles or smaller test piles, or in house methods derived from past project experience. This has led to inaccurate predictions thought to be associated with the difference in size between jacket/test piles and monopiles; additionally, predictions from different companies often vary significantly. Subsequently, decision-makers often have low confidence in such predictions, which often leads to conservative decision making during installation. This may result in the use of larger than necessary hammers and/or driving induced fatigue predictions, and the inclusion of stand-by drilling rigs.
This paper is based on the back-analysis of over 200 monopile installation records covering different projects, pile geometries and varied geologies. This allowed a detailed review of prediction methodologies and a revised understanding of how the predictions are affected by the engineering properties of the soil. Several interruptions were noted within the driving records, enabling an evaluation of how the observed set up for monopiles compares to previously published records for jacket piles. A new model was then developed to cover the assessment of installation interruptions for large diameter piles.