With the advantages of low construction costs and rapid installation, suction caissons are widely used as foundations in offshore engineering. This paper investigates the behavior of suction caisson foundations located in sandy soil under horizontal cyclic loads. The upgraded simple anisotropic sand constitutive model with memory surface (SANISAND-MS model) is employed to accurately capture the sand's cyclic behavior. To calibrate the parameters of the upgraded SANISAND-MS model, a series of triaxial drained monotonic and cyclic tests was performed. The effects of load idealization and loading sequence on the cyclic behavior of sand are studied based on the element test results, and the effects of load idealization on the cyclic response of suction caissons are studied from a finite-element simulation perspective. The triaxial test results indicate that load idealization slightly affects strain accumulation in both loose and dense sand. Based on simulation results, it is found that the loading sequence of load packages with varying amplitudes has a minor effect on the rotation accumulation of the suction caisson. The current load idealization method used in the engineering design practice of suction caissons is acceptable under drained conditions.

Changes in soil properties due to loading and consolidation during the life of infrastructure affect the soil response to future events. This concept is encapsulated in the whole-life geotechnical design approach which accounts for the evolution of properties such as strength, stiffness and consolidation coefficient, to improve forecasts of system response through and beyond the design life. This paper explores the changing properties of a soft clay from episodes of pre-failure cyclic loading and consolidation through a series of stress-controlled cyclic direct simple shear (DSS) tests. The scenario is relevant to offshore applications where infrastructure is subject to cyclic seasonal loading, and is particularly relevant to floating offshore wind anchoring systems as these are located in deeper water, farther from shore where soft clays are common. The results quantify the effect of cyclic stress amplitude, number of cycles per packet, and number of consolidation intervals, on the clay properties. The results show increases in undrained strength by up to 70%, stiffness by up to 50% and consolidation coefficient by a factor of up to 30, highlighting the importance of accounting for whole-life effects for reliable and efficient geotechnical design.

Integrated field and laboratory characterisation of geomaterial behaviour is critical to foundation analysis and design for a wide range of offshore and onshore infrastructure. Challenges include the need for high -quality sampling, addressing natural and induced micro -to -macro structures, and applying soil and stress states that represent both in -situ and in-service conditions. This paper draws on the Authors' recent research with stiff glacial till, dense marine sand and low -to -medium density chalk, and focuses particularly on these geomaterials' mechanical behaviour, from small strains to failure, their anisotropy and response to cyclic loading. It considers a range of in -situ techniques as well as highly instrumented monotonic and cyclic stress -path triaxial experiments and hollow cylinder apparatus tests. The outcomes are shown to have important implications for the analysis of large driven piles under monotonic -and -cyclic, axial -and -lateral loading, and the development of practical design methods. Also highlighted are the needs for approaches that integrate field observations, advanced sampling and laboratory testing, numerical and theoretical modelling.

Plate anchors have become an attractive technology for anchoring offshore floating facilities such as floating renewable energy devices because they provide high holding capacity relative to their dry weight. This allows for the use of smaller anchors (relative to a driven or suction-installed pile), which provide cost savings on production, transport, and installation. Loads delivered to the anchor via mooring lines may increase pore water pressure in fine-grained soils. This excess pore pressure will dissipate with time, resulting in a local increase in the undrained shear strength of the soil surrounding the anchor, increasing the capacity. There may be opportunities to consider these capacity increases if the consolidation process occurs over time periods that are short relative to the lifetime of the facility. This paper considers the use of drainage channels in a plate to make the anchor permeable and quicken consolidation times. Experimental data generated from model-scale experiments conducted in a geotechnical centrifuge show (for the anchor design tested) that excess pore pressure just above the anchor dissipated almost an order of magnitude faster for a permeable anchor, and that after full consolidation, the permeable anchor capacity was higher. The latter finding was not anticipated and is believed to be due to changes in load distribution resulting from the rapid reduction in negative excess pore pressure underneath the permeable anchor.