Pile jetting in plane strain: Small-scale modelling of monopiles

Large monopiles are used extensively in offshore applications, however current installation methods have negative environmental consequences. Water jetting can be implemented to reduce the need for traditional installation techniques, saving time and reducing environmental concerns. Although water jetting has been used since the 1950s, its underlying mechanics are poorly understood. Thus, an innovative experimental methodology has been used to model a segment of a monopile foundation in plane strain, installing into medium dense sand. Through experimental work, both Stages 1 and 2 of a Shepley and Bolton (2014) jetting mechanism have been observed. PIV and instrumental data have been used to verify mechanisms, suggesting a localised fluidized region around piles during stage 1 and a global movement of soil medium during stage 2. Load tests of Jetted piles have shown a reduction in bearing capacity compared to non-jetted piles. Jetting properties at the base of the pile have been shown to have a significant impact upon the initial stiffness response and final performance of foundations.