Proceedings-DFI-India 2016: 6th Conference on Deep Foundation Technologies for Infrastructure Development in India, (DFI)
Influence of Pile Geometry on the Dynamic Response of an Under-Reamed Pile
Muzammil M. Jr., RDSO, Lucknow, Uttar Pradesh, India, Bharathi M., Saran S., and Mukerjee S., IIT Roorkee, Roorkee, Uttarakhand, India
This paper presents the results of in-situ tests conducted on a set of under-reamed piles in a silty sand deposit. Three piles (i.e. vertical, vertical with one bulb and vertical with two bulbs) of diameter 0.2 m were cast upto a depth of 5 m. The pile cap had four foundation bolts cast into it so that a mechanical oscillatormotor assembly could be mounted centrally on it. The oscillator-motor assembly was used to generate purely sinusoidal dynamic forces, in either horizontal or vertical directions. For both horizontal and vertical vibration cases, it was observed that (i) the natural frequencies decreased with an increase in the excitation force level, (ii) for the same excitation level, the natural frequencies as well as the maximum amplitude of vibration are almost the same irrespective of the pile geometry i.e. number of bulbs in the pile, indicating that the full pile length is not being excited. For the vertical vibration case, the soil-pile stiffness at frequencies, before resonance, were observed to be higher than those at frequencies after resonance. In the horizontal vibration case, the stiffness of the soil-pile system was found to be decreasing with an increase in the excitation force level. The damping ratio was found to be increasing with an increase in the excitation force level.
|article #2233; publication #1020 (INDIA-2016)|