Non-linear analysis of a torsionally loaded single pile and pile groups in clay soil

The main aim of this research is to investigate and analyse the non-linear behaviour of a single pile and pile groups with rigid pile caps subjected to torsional loading in clay soil. Plaxis 3D software is utilised, considering pile groups (1 × 2, 2 × 2, 3 × 2 and 3 × 3), different L/d ratios (L/d = 20, 30 and 50), spacing (S/d = 3, 4 and 6), depth of embedment (f/t = 1, 0.5 and 0), diameter (d = 0.76 m, 1.5 m and 2 m) and clay soil consistency (soft and stiff). The applied torque is found to be mainly resisted by the lateral and torsional resistances of each pile in a pile group, and quantitative evaluation of their contributions is conducted. From the numerical results, it is found that the failure torque of a single pile increases with pile length (57–257%), pile diameter (198–388%) and the depth of embedment of piles (6–206%). The torsional resistance of the groups increases with the pile length (7–22.5%), pile spacing (68–228%), pile diameter (176–281%), the depth of the embedment of piles (10–43%) and soil consistency (soft to stiff), but the torsional contribution decreases as the group size and spacing increases.