Estimating suction limits during suction caisson installation in sand using an equivalent seepage-resistance framework

Suction caissons are widely used as offshore foundations, but estimating the installation suction limit in sand remains challenging during medium-to-deep penetration. Conventional formulations may underestimate attainable suction because they idealize the seepage field using fixed or numerically calibrated flow geometries. This study investigates suction caisson installation in saturated sand through 1-g model tests and CPT-based jacking calibration. Suction-assisted penetration reached approximately 80%-86% of the skirt length, and the observed terminal suctions consistently exceeded the S&R estimates. To interpret this depth-dependent increase, an equivalent seepage-resistance framework is proposed by decomposing the suction-induced hydraulic head loss into confined-plug, external seepage, and local entrance-loss contributions. The framework provides a measured-discharge form and a Q -eliminated form when discharge measurements are unavailable. Axisymmetric finite-volume analysis showed that the geometry-based external resistance differed from numerical results by at most 2.07% over 0.5 ≤ x ≤ 2.0 . In the present tests, errors relative to the observed means were 6%–14% for the measured-discharge form and within 7% for the Q -eliminated form. Comparisons with published field, centrifuge, and 1-g records show that the Q -eliminated form provides consistent limiting-suction estimates for piping-associated cases. The framework provides a mechanics-based tool for estimating suction limits during installation in sand.