Driving Stresses in Concrete Piles

Abstract

Dynamic tests were performed in Miami, Florida, on three 18-in. square, 60-ft long (45.7-cm square, 18.3-m long) prestressed concrete piles. Each pile was driven with a different size open end diesel hammer. Strains during driving were measured at the midlength of the pile and at the pile top. Set rebound and ram stroke were also measured. Since some current specifications include pile-ram weight ratios for the purpose of limiting driving stresses in concrete pile, this test was useful to investigate how successful the code restrictions were in limiting potentially damaging stresses due to various size hammers. Measured tensile and compressive stresses were compared with hammer size, pile net displacements, ram stroke, and hammer throttle setting to determine conditions which were most likely to produce damaging tensile or compressive stresses. It was found that pile-ram weight ratio is an unsatisfactory parameter for controlling hammer selection for open end diesel hammers. In fact, the use of this ratio can lead to excessive pile stresses. Finally, alternate procedure for selecting driving equipment are presented. ;Author;