Group Effects of TLP Tendon Driven Piles in Normally Consolidated (NC) Clay

Long large-diameter driven piles (i.e., 2.0∼3.0m-diameter piles with a 100m penetration or deeper) have been usually used as Tension Leg Platforms’ (TLP) foundations in normally consolidated clay. In order to optimize a design, TLP designers would like to reduce the pile spacing, resulting in a pile group effect issue for pile geotechnical designers. This paper presents the development of a three-Dimensional Finite Element Analysis (3D FEA) model using Finite Element Code PLAXIS 3D to investigate the pile group effect of the TLP driven piles in normally consolidated clay. Using this model, a series of FEA runs were carried out. Firstly, the FEA model was used to examine the mobilization of axial capacity and the related group effect of a pile group, with various numbers of piles per group and different pile spacing. Secondly, the FEA model was used to investigate the group effects on the lateral capacity of a pile group, with respects of mobilization of lateral capacity, influence of loading direction, influence of pile spacing, and influence of number of piles in one group. These FEA results were also compared with the literature studies. Finally, recommendations on pile group effects for both axial capacity and lateral capacity were provided for TLP driven pile geotechnical designs in normally consolidated clay.