Inclined loading of suction caisson anchors in calcareous sand with particle breakage

Despite the high cost-effective potential of using suction caisson anchors for mooring floating facilities for harvesting various marine resources, it is not being considered in sites with calcareous sediments largely due to the lack of understanding of anchor-sand interaction, particularly where sand particles are prone to breakage. This paper reports the behaviour of suction caisson anchors under inclined monotonic loading in medium dense to dense calcareous sands. Three-dimensional finite element simulations were conducted using a recently presented modified Mohr-Coulomb model incorporating particle breakage (MMC-PB). The MMC-PB model was validated against centrifuge test data, with good agreement obtained. Extensive parametric analyses were then carried out varying sand relative density, caisson geometry, padeye location, and loading angle. Soil failure mechanisms were exposed, and the distribution of particle breakage was tracked and quantified, to provide insight into the behaviour of suction caisson anchors. Anchor capacity under inclined loading was presented as failure envelopes expressed in terms of dimensionless vertical (V) and horizontal (H) components of anchor resistance. A calculation framework was proposed distilling 360 numerical simulations into easy-to-use equations for developing routine V-H failure envelopes. The understanding and framework will provide confidence in designing suction caisson anchors in calcareous sand.