Dynamic lateral response of under-reamed vertical and batter piles

Abstract

Dynamic lateral response of three under-ream reinforced concrete piles constructed in silty sand {vertical, P1 (β = 0°); and batter piles P2 (β = 10°) and P3 (β = 20°)} having equal length of 2.5 m, shaft diameter 0.2 m and under-ream bulb of diameter 0.5 m were considered for this experimental study. Dynamic loads were generated using an oscillator motor assembly mounted on top of pile cap and the response of these piles were recorded in real time using three accelerometers placed along the depth of the pile cap. These piles were subjected to varying dynamic load by changing the eccentricity setting of the oscillator in the frequency range of 0–40 Hz. The test results show that the resonant frequency of the soil-pile system decreases; and peak lateral displacement increases with increase in the force level. The variation of rotational stiffness and the damping ratio of the soil-pile system with force level did not follow a clear trend. Thus the presence of an under-ream bulb in a batter pile does not have a significant influence on the lateral behaviour of batter piles.