Calculation Method for Uplift Capacity of Suction Caisson in Sand Considering Different Drainage Conditions

Abstract

Uplift capacity of suction caissons is one of the main concerns in the design of jackets with multi-caissons supported offshore wind turbine. The uplift movement of suction caissons leads to soil stress variation and increases the difficulty to predict the uplift capacity. In this paper, a calculation method considering soil stress release and differential pressure contribution is proposed to predict the uplift capacity of caisson. Firstly, a series of numerical simulations based on the SANISAND model are conducted to study the uplift responses of suction caisson in sand, and it is verified with centrifuge test results. Considering the soil drainage condition during caisson being pulled out, the fully drained, partially drained and undrained are divided, and an equation is provided to assess differential pressure beneath the caisson lid incorporating the effects of main factors. Based on the above simulation results, a calculation method is proposed to calculate the uplift capacity of caissons. The prediction results are compared with the centrifuge model tests and previous studies, which indicate that the prediction accuracy is much improved. This proposed method contributes to the more accurate assessment of uplift capacity of suction caisson in sand.

Numerical model for suction anchor under vertical impact loading

“…It illustrates the three components of the uplift resistance F res, including the gravity of suction anchor Wfou, skirt wall friction Ffri, and the suction beneath the anchor lid Fp. As the drainage condition of seabed soil changes from fully drained to undrained, the existence of differential pressure greatly improves the uplift resistance of suction anchor, and the undrained pullout capability can be 10 times or even more than its fully drained pullout capacity [8]. Nonetheless, the motion of mooring foundation is typically irregular during service, and the suction anchor will not be extracted at a steady speed.…”

“…Based on the drainage conditions of fully drained, partially drained, and undrained, the failure processes of suction IOP Publishing doi:10.1088/1755-1315/1332/1/012035 2 anchors are divided into three categories, including partial shear failure, partial tensile failure, and overall reverse failure [5]. The obvious permeability of sand generates a seepage field within the soil domain [6,7], which has a major impact on the accumulation of differential pressure [8]. The pullout capacity of suction anchor under various drainage conditions has been investigated by model tests [9,10], field tests [11], and centrifuge tests [12].…”

Seabed structures and foundations related to deep‐sea resource development: A review based on design and research

“…The penetration evaluation is usually carried out based on the principles proposed by Andersen and Jostad (1999). Such evaluation includes penetration resistance, anchor self-weight, required under-pressure, allowable under-pressure, soil heave, and maximum penetration depth (Xu et al, 2023). The penetration resistance R TOT is evaluated by…”

“…The penetration evaluation is usually carried out based on the principles proposed by Andersen and Jostad (1999). Such evaluation includes penetration resistance, anchor self‐weight, required under‐pressure, allowable under‐pressure, soil heave, and maximum penetration depth (Xu et al, 2023). The penetration resistance R TOT is evaluated by $$${R}_{\mathrm{TOT}}={R}_{\mathrm{side}}+{R}_{\mathrm{tip}},$$$where R side is the resistance along the wall sides due to the side shear, and R tip is the bearing capacity at the skirt tip.…”