Transmission Of Foundation Vibrations

Ground vibrations triggered by machine foundations can influence adjacent structures in both serviceability and durability limit states. In order to control the potential damage to structures in the vicinity of the source, it is important to be able to predict the response of the surrounding soil. This study investigates the soil response induced by a harmonically loaded foundation with coupled swaying-rocking motion embedded in a soil layer over a half-space with the use of finite-element models developed in Abaqus. The soil medium is modelled in the frequency-domain as a linearly elastic material with frequency-independent damping. Appropriate ‘non-reflective’ conditions are applied at the boundaries to minimise wave reflections. Initially, an axisymmetric model of homogeneous half-space is developed, with anti-symmetric boundary conditions applied to simulate coupled swaying-rocking oscillations. To establish a general trend for the spatial attenuation of vibration amplitude, multi-variable functions are fitted to the results obtained from these analyses. The proposed relations are subsequently employed for a preliminary assessment of the vibrations transmitted by the shaking table and reaction mass of the new University of Bristol Soil Foundation Soil Structure Interaction Facility (SoFSI). Noting that the final configuration of the facility is still under design and that the soil properties have not been accurately established yet, this case study allows for useful comparisons between analytical solutions and a full three-dimensional finite-element simulation