Effect of Pile Arrangements on the Dynamic Coupled Response of Pile Groups

This paper presents both experimental and analytical investigation to monitor the effect of dynamic pile-soil-pile interaction on the nonlinear coupled response of a 6-pile group placing in different arrangements of piles under rotating machine induced vibrations. Another aspect of the present study is the theoretical prediction of parameters responsible for the nonlinear coupled response of the pile foundation. The pile groups comprised of hollow steel piles with an outer diameter of 0.114 m and a length of 3 m. Coupled vibration field tests are performed on the pile groups laid in two different set of pile arrangements (2 \(\times\) 3 and 3 \(\times\) 2 pile groups) to obtain the dynamic horizontal and rocking responses of the pile groups under different eccentric moments. For theoretical study, the continuum approach with superposition method is used to determine the nonlinear dynamic responses of the pile groups. The analytical frequency-amplitude responses for both types of vibrating displacements are compared with the dynamic field test results and the variations of the influencing parameters for the nonlinear dynamic response of the soil-pile system are predicted for coupled vibration. For 3 × 2 pile group, the resonant frequencies are found lower and resonant amplitudes are found higher than the values of the 2 × 3 pile group for all eccentric moments. It is also observed that the stiffness and damping of the 3 × 2 pile group shows lesser values than the 2 × 3 pile group even if the input analytical parameters are same for both the pile groups. From the results, it can be concluded that the effect of dynamic pile-soil-pile interaction is more pronounced for 3 × 2 pile group as compared to the 2 × 3 pile group.