Battered minipiles in fine-grained soils: Soil-structure interaction

The ultimate lateral load capacity of battered minipiles is investigated in fine-grained soil via field testing equipped with optic fibre sensing and consequently complemented with finite element modelling. The numerical model developed in COMSOL Multiphysics was validated against (i) field-obtained force-displacement data of minipiles battered at 25° and (ii) strain profile along a vertical minipile shaft. The numerical model was then further used to predict force-displacement curves for minipiles with batter angles of 15°, 30° and 45° using the full-scale pile and field soil parameters. The model helps in understanding how the combination of normal and shear stresses along the minipile shaft leads to the optimum batter angle of 30° when subjected to lateral loading. Furthermore, a parametric study was performed to comprehend the effect of apparent cohesion and minipile length on the optimum batter angle. When the apparent cohesion of the soil was reduced, the optimum angle changed from +30° to +45° in the case of positive battered minipiles. A change in optimum batter angle was observed when the minipile length was increased as well. These varying parameters influenced the optimum batter angle of laterally loaded minipiles, and the numerically obtained normal and shear stress profile justified this behaviour.