Prediction of Downdrag Forces in End-Bearing Piles

A method of analysis based on elastec theory is presented for the development of downdrag forces in an end-bearing pile in a consolidating soil layer. The analysis permits consideration of pile-soil slip and of the rate of development of downdrag force in the pile with time. Parametric solutions are presented for the magnitude and rate of development of maximum downdrag force and pile settlement with time, and are expressed in dimensionless form in terms of the values for full pile-soil slip. The solutions enable a ready appreciation of the combinations of pile-soil parameters for which full slip occurs and of the transition from the case of full slip to the fully elastic case. Some of the available data on pile-soil parameters and soil deformation parameters are presented, and comparisons are made between measured downdrag force and pile shortening in field tests and values predicted from the theory.