Centrifuge testing on ordinary and hybrid suction caissons subjected to cyclic lateral loading

Abstract

Hybrid Suction Caissons (HSCs) are innovative structures that amalgamate a shallow foundation (mat or skirted) with an internal caisson. The results of 40g centrifuge tests conducted on the Ordinary Suction Caisson (OSC) and two HSC types installed in medium-dense saturated sand, enduring long-term lateral cyclic loading (600 cycles), are analyzed and discussed in this paper. This research incorporates combined cyclic loading tests, encompassing one-way and two-way cycles in a singular examination to simulate the typhoon and service conditions before and after. The major findings include: (i) HSC, compared to OSC, can effectively harness accumulated rotations of the foundation induced by both one-way and two-way cyclic loading, (ii) adding an outer skirt to HSC, attached to an inner caisson and mat foundation, reduces considerably accumulated rotations induced by one-way cycles, (iii) cyclic loading does not change the unloading stiffness of OSC and HSC without an outer skirt, while increases the unloading stiffness of HSC with an outer skirt, and (iv) analyzing and designing OWT foundations should consider the combined cyclic loading scenario, rather than solely relying on one-way or two-way cyclic loading regimes. Based on the results, a power formula is proposed for estimating caissons' rotations stemming from long-term cyclic loading.