Predicting Driving Stresses in Piles

Abstract

Reliable methods for the prediction of pile stresses are necessary because of the ever increasing damage and financial loss incurred on many piling projects due to improper selection of driving hammer. There is a delicate balance between pile stress, driving resistance, and hammer-to-pile weight ratio. Too large a hammer may destroy the pile whereas too small may not be adequate to drive the piles effectively. Existing methods of pile dynamic analysis have been found to give misleading results for certain driving conditions. This paper presents rigorous analytical procedures based on the theory of longitudinal wave transmission in conjunction with the equations of motion of pile-hammer system. The various cases of pile resistance distribution considered are: (1) 100% friction with uniform distribution; (2) 100% friction with triangular distribution; (3) 50% tip resistance and 50% uniformly distributed friction; (4) 50% tip resistance and 50% friction with triangular distribution; and (5) 100% point resistance. Charts are developed for steel, concrete, and wood piles. A method for selection of the most appropriate driving hammer is presented.