Laboratory evaluation of torque and uplift capacity relations for screw piles in granular soil

Abstract

Model screw piles of different geometry and dimension are installed in uniform density granular sand beds by application of torque at pile head. On installation the piles are subjected to uplift load. Devices are fabricated to apply and :neasure torque, uplift load and deflections. Effect of pile geometry and blade dimension on the torque required fOr installation and uplift capacity of the .piles have been evaluated. Mathematical expressions are derived to relate pile geometry (blade dimension and spacing) with torque required for installation and uplift capacity. A good correlation is found between measured tOrque at pile head with that calculated from the derived mathematical expression and also between measured uplift capacity with that calculated from derived expression. A good correlation is Observed between the torque required for installing a pile and its uplift capacity. Based on the experimental results emperical relations are proposed to relate driving torque with uplift capacity. Some aspects of screw pile installations in granular soils and uplift capacity evaluations are highlighted.