PARTICLES 2023

On the application of the material point method for spudcan penetration

  • Sugiyama, Yuri (Port and Airport Research Institute)
  • Nakamura, Keita (Port and Airport Research Institute)

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In order to reduce greenhouse gas emissions in the medium to long term, the introduction of offshore wind power generation as renewable energy is being promoted worldwide. A jack-up vessel is used for the construction of offshore wind power generation facilities, and offshore wind turbines are constructed by penetrating spudcans and supporting the legs on the ground. Therefore, it is imperative to understand the bearing characteristics of the ground. Numerous model experiments and numerical analysis have been carried out in the past on the stability of legs during spudcan penetration on sandy ground, cohesive soil, and their multi-layers. However, there are still many jack-up accident, such as punch-through, in which spudcan penetrate into the cohesive soil below because it cannot be supported by the upper sandy soil during operation. In this study, a parametric study using MPM-rigid body coupling technique was conducted to examine the relationship between spudcan penetration depth and bearing capacity. Furthermore, in order to verify the validity of the numerical analysis results, centrifugal model experiments of spudcan penetration were carried out using sandy soil, mixed soil, and cohesive soil. As a result, the bearing capacity of the sandy soil increased approximately linearly with the penetration depth, and the numerical analysis showed good match with the experiment. In the mixed soil containing 20% of the fine fraction, the bearing capacity decreased by about 40% compared to the sandy soil. The reason for this is that the bearing capacity is affected not only by the deformation modulus and strength of the ground, but also by partial drainage. The MPM used in this analysis cannot consider partial drainage, but by using the friction angle obtained by triaxial tests conducted under partial drainage conditions, it was possible to grasp the relationship between penetration depth and bearing capacity.