Recent Trends in Driven Pile Foundations in New England

Driven pile foundations are a commonly used deep foundation alternative throughout the U.S. and the world. Over the last ten years or so, design stresses for these pile foundations, particularly steel H-piles and pipe, have been trending higher due to detailed evaluation and understanding of soil/rock conditions and increased confidence in quality control and testing methodologies. Design stresses in steel piles have been routinely approaching and/or exceeding 20 ksi in order to increase the allowable pile loads and enable the driven steel pile industry to compete more efficiently with other deep foundation types such as micro-piles or drilled shafts. The use of higher stresses has now placed more emphasis on obtaining and classifying rock cores, particularly for the larger HP sections, where design loads of 200–300 t or more are now being used. The pile capacity is now controlled by the rock quality and/or the drivability of the pile rather than the limitations on the structural steel design. As a result, larger hydraulic hammers with more efficient energy transfer and bigger load test frames are necessary for successful installation. For other applications, in order to avoid driving to rock, which in some cases can be over 250 ft deep, other types of innovative steel foundations are being used. These steel foundations have not commonly been used in New England. They are trademarked, fabricated, non-traditional pipe pile sections that improve soil resistance to keep pile penetration lengths relatively short with reasonably high design loads that would not normally be obtainable with standard steel or pipe piles. This paper discusses the current trends in New England with regard to more frequent use of high capacity H-piles driven to rock and the emerging use of non-traditional pipe piles driven to shallow depths in sandy soils. Design challenges and case history examples are discussed.