Measurements and predictions of vibration response of end-bearing pile group in soft clay due to vertical ground surface load

Abstract

Ground-borne vibration from roads or railways is a growing concern in the planning of new buildings in urban environments. Vibration assessment is often based on initial measurements of the free field vibrations to estimate building vibrations by either empirical or numerical procedures. Dynamic interaction between the soil and the foundation has an important influence on the transmitted vibrations, especially for embedded foundations, and should therefore be properly accounted for. This paper presents the results from a series of full-scale field experiments that were performed to characterise the vibration response of an end-bearing pile group foundation in soft clay subjected to a dynamic load applied at the ground surface. Controlled dynamic excitation is applied vertically at the ground surface from 10 and 20 m horizontal distance using an electrodynamic inertial shaker. Accelerations are measured at different construction stages: prior to construction, after driving of the piles and after completion of the pile cap. Predictions from a numerical model and from a hybrid method utilising measurement data acquired in an earlier construction stage are both validated with the data from the field tests. The results indicate that the relationship between the amplitudes of the vertical foundation and free field responses are insensitive to source–receiver distance. It is also found that pile–soil–pile interaction has an important influence on the vertical response of the piles.