Installation design of a large tubular caisson in the spatially varying seabed

The installation of large steel tubular caissons, used as protection for underwater production systems, is still a challenge. To evaluate the reliability of installation, soil spatial variability is accounted for in this study through two-dimensional random field establishments and Monte Carlo simulation. As vertical random parameters are identified by field CPT data, the effect of the horizontal scale of fluctuation (δh) is explored, which becomes significant due to the extremely large diameter of the caisson. Probability distributions of self-weight penetration, inclination angle, and the ultimate soil resistance with various δh are derived from conventional installation analyses with spatially varying soil domains. It shows that increasing δh reduces the likelihood of over-tilt, yet raises the possibility of vibratory drivability refusal (failure probability). The effect of stiffeners during caisson installation is also studied, including an increase in penetration resistance and failure probability. This analysis sheds light on the impact of the soil correlation distance as well as caisson stiffeners and is useful to the reliable installation design of the large tubular caisson, particularly in layered soil. © 2022 Elsevier Ltd