Design and Performance of an Electro-Pneumatic Pile Hammer for Laboratory Applications

Small piles used in research programs have generally been installed by pushing or driving using slow mechanical drop hammers, because of the expense and technical difficulties associated with manufacture of realistic small-scale pile driving hammers. However, pushing does not model inertial effects and slow driving does not model diffusive effects in the soil. It remains to be demonstrated whether these effects are important or not. To help clarify this issue, an electronically controlled, single-acting air hammer, with a rated energy of 211 J (156 ft ·1b), and an operating frequency of up to 1.2 Hz, was designed and built. The hammer was used successfully to drive 90 mm (3.5 in.) diameter piles into dense sand under a confining pressure of 138 kPa (20 psi). The behavior of the hammer was documented using detailed measurements of time-dependent ram movements, accelerations, and chamber pressures. This paper is concerned with the design and performance of the hammer.