Installation and Monotonic Pullout of a Suction Caisson Anchor in Calcareous Silt: Fid-Bau Portal

Installation and Monotonic Pullout of a Suction Caisson Anchor in Calcareous Silt

Koh, Kai Xiang / Hossain, Muhammad Shazzad / Kim, Youngho

This paper reports results from a series of model tests undertaken to provide insight into the behavior of a stiffened caisson anchor during installation and monotonic pullout in lightly overconsolidated calcareous silt. The tests were carried out in a beam centrifuge, varying the installation process (jacked in or jacked in followed by suction-assisted installation), and the consolidation period before anchor pullout. The mudline load inclination was also varied to encompass various mooring configurations. The centrifuge data were used to calibrate analytical installation and vertical pullout capacity models, based on conventional bearing and frictional resistance factors but with strain rate-dependent and strain-softened undrained shear strength for the soil. Piezocone-based direct design approaches were also proposed, deriving end-bearing and frictional resistance from cone tip resistance and sleeve friction, respectively. Holding capacity of suction caisson under inclined loading was presented as failure envelopes expressed in terms of dimensionless vertical and horizontal components of caisson net resistance, which agreed well with a plastic limit analysis-based envelope developed for suction caissons in clay. The regain of anchor capacity was found to be in good agreement with predictions based on the cavity expansion framework.