Experimental Technique for Impact Testing of Concrete Piles

This paper proposes an experimental method to evaluate the structural performance of full-scale piles subjected to pile driving condition. A pendulum mechanism was used to deliver impact forces on a pile which was placed horizontally on supports and restrained at the tip with large blocks to mimic the critical real-world condition of reaching a strong/hard layer. Accordingly, driving forces were transferred to the pile by an impactor that was designed to deliver impact energies comparable to those of typical pile driving hammers. To swing the impactor and to guarantee a stable motion, four cables connected to two out of three 50 ft. tall steel pylons were attached to the impactor through lifting eyebolts, while another cable pulled back the impactor toward the third pylon to a desired drop height from where the impactor was released. The restraining blocks placed at the tip also minimized excessive displacement. Friction between the restraining blocks and the piles as well as friction between the soil and the pile surface limited displacement at the pile tip. The experimental method evaluated in this study effectively simulated pile driving for assessing structural performance and pile driveability, especially when evaluating new materials with an unknown impact response. This method of pile testing provided laboratory conditions for a pile impact test that is usually carried out in the field.