The influence of pile–soil–pile interaction on the vertical response of end-bearing pile groups in soil on bedrock subjected to a vertical load at the soil’s surface

The influence of pile–soil–pile interaction on the vertical response of end-bearing pile groups when subjected to an incident wave field generated from a vertical load at the soil’s surface is investigated. A numerical model which allows for considering or disregarding the influence of pile–soil–pile interaction is adopted. Vertical end-bearing pile groups with different pile axial stiffness and pile-to-pile spacing are considered. This study shows that in contrast to floating piles in homogeneous soil, the interaction effects caused by wave scattering between the piles are important for end-bearing piles. These may either reduce or amplify the group response, depending on the wavelength in the soil, the spacing between the piles, the pile slenderness and the pile–soil stiffness ratio. The interaction between the piles which are aligned in the direction transverse to the propagation direction of the incident wave field is found to amplify the group response at certain frequencies. Reducing the pile spacing in this direction is found to influence the vertical vibration response of end-bearing pile group foundations considerably by shifting the amplification effects due to pile–soil–pile interaction to higher frequencies.