Pile Setup and Axial Capacity Gain for Driven Piles Installed Using Impact Hammer versus Vibratory System

Due to the presence of soft saturated cohesive soils in New Orleans and vicinity, most civil engineering structures are supported on deep foundations, consisting of timber piles, precast concrete piles, open or closed end pipe piles, or steel H-piles. The piles at a project site derive their load carrying capacity from (a) “skin friction” along their embedded lengths and (b) “end bearing” when tipped firmly into dense sand or stiff clays. The piles are generally driven in the ground using pile-driving rigs equipped with (a) impact hammer or (b) vibratory equipment. Impact hammers drive the pile by inducing impact on the pile with a falling ram which moves the pile incrementally into the ground. Conversely, a vibratory system installs pile into the ground by applying a rapidly alternating force to the pile using rotating eccentric weights. Impact hammers produce vibration to the ground which can be detrimental to a nearby structure. Consequently, vibratory system has gained popularity in installing large number of pile types. However, the long term effects of vibratory system on soil-pile interaction and pile setup is not properly understood. The main objectives of this research study were to evaluate the set-up phenomenon for four different steel piles driven in soft clay formation in southeast Louisiana using impact hammer and vibratory pile driving system. This paper presents the results of several dynamic load tests performed on these piles over a period of several weeks and summarizes the effects of installation procedure on pile capacity gain.