Dynamic vertical response of model piles — experimental and analytical investigations

Abstract

Dynamic response characteristics of reinforced concrete model piles were investigated in the field under varying levels of vertical harmonic excitation. In the investigations single piles and 2 × 2 group piles with length to diameter ratios 10, 15 and 20. For group piles, spacing to diameter ratios of 2, 3 and 4 for each length to diameter ratio were used. In both the cases, two different conditions of pile cap — embedded into soil and above the ground surface, were considered in this investigation. The measured response was compared with the response obtained by different analytical methods. The stiffness and damping of piles under vertical vibration were computed by two different analytical approaches — (i) Novak's frequency independent solutions with static interaction factor for parabolic soil profile and (ii) Novak's complex frequency dependent analytical solutions with dynamic interaction factor approach for layered media. From the comparison of these theories with the experimental data it was found that the Novak's frequency dependent solutions with dynamic interaction factor approach produced reasonable estimates of the experimental results. In this study the influence of excitation intensity, static load on pile and different contact condition of pile cap with soil on the dynamic behaviour of pile foundation are reported.