Analytical study of piles behavior for marine challenging substructures

Based on a new categorization, significancy and feasibility of vector-acting foundations for offshore challenging substructures are emphasized. A marine challenging status is typically related to loading, investigations, subsurface, environment, construction and sustainability requirements. The issue of the interaction of piles and complex subsoil is discussed in this paper. Three scenarios are studied comprising sensitive deposits at the full depth, the most impressive one, compressible deposits at the top layer and soft soil underlain by strong deposits. The role of CPTu records is addressed in recognition of problematic layers, geotechnical design and embedment depth designation. The effect of soil sensitivity on shaft and toe resistance is quantified through static analysis and reduction factors are suggested. Since bearing capacity, settlement and axial load are interactive, the neutral plane concept is applied, unifying the mentioned aspects. Through the neutral plane approach and considering the downdrag force due to the collapse of sensitive soil, primary design criteria incorporating sensitivity are discussed and quantified. Applying ground modification as a supplement for deep foundations is realized through two case studies, leading to enhancement in geotechnical performance. Overall, the mentioned phenomena must be discovered comprehensively in extraordinary conditions, aiming for a safe, reliable, knowledge-based and optimum design.