An Experimental Investigation for Soil-pile Interaction Under Harmonic Load

In the present paper, the soil-pile model is tested on a shake table subjected harmonic load. A reduced-scale model (1:20) based on the similitude rule for a group of piles with a pile cap is used in the present study. The sinusoidal base excitation with varying frequencies in the range 3 Hz to 12 Hz and base acceleration ranging from 0.05 to 0.3 g are used as input base excitations for shake table testing. The amplifications at various depths of a cohesionless soil deposit without and with a group of piles are studied using shake table testing. Also, behaviour of group of piles embedded in soil is investigated in terms of variation in the strain levels and pile bending moment along the depth without and with pile cap mass with floating tip condition. It is observed from test results that the amplification of acceleration near top of the soil column is up to 4.266 times the base acceleration in the soil only cases. However, the amplification of acceleration near top of the soil column is up to 4.00 times the base acceleration when the model piles are placed inside the soil and is up to 4.66 times the base acceleration at the pile cap level. It is also observed that, when the model piles along with pile cap and pile cap mass are placed inside the soil, the amplification on base acceleration near top of the soil column and at the pile cap level are up to 3.986 and 4.67 times, respectively. The pile bending moments are evaluated by mounting the strain gauges at different depths along the pile surface. These are also evaluated using analytical methods, and the comparison of the results shows reasonable agreement. It is also observed that the pile bending moment at centre pile is lesser compared to pile bending moment of corner piles which may be attributed to effects of confinement. The present study will be useful guide for pile designers to obtain pile response under dynamic loads.