Summary
This Paper describes an investigation which included model-experiments and full-scale loading tests on screw piles and cylinders, observations on the settlement of piles in actual structures, the derivation of a theory of bearing capacity, a check on the relationship between the driving torque and the bearing capacity of the pile, and the formulation of design rules.
Two important factors, the first of which does not appear to have been appreciated previously, emerge from this investigation: they are that the value of the coefficient of earth-pressure at rest is a critical factor in the bearing capacity of structures founded in a frictional medium, and that the effect of screwing a cylinder with a closed nose into dense sand is to raise the horizontal earth-pressure considerably and so to effect a very large increase in the bearing capacity.
