Civil Engineering Association

The vibration response of piled foundations to inertial and underground railway induced loadings

Vibrations and re-radiated noise in buildings induced by (underground) railway traffic are a major environmental concern. Vibrations are generated at the wheel-rail interface and propagate through the soil into buildings, where they cause annoyance to inhabitants. During the last decades, a lot of research has been performed to search for efficient and cost-effective vibration countermeasures. This dissertation is concerned with the dynamic behaviour of piled foundations. A model for piled foundations which accounts for the fundamental behaviour of each pile and the interaction between neighbouring piles, through wave propagation in the soil, is developed. It is a boundary element
model, formulated in the frequency domain, based on an existing single pile model.
The model is used to validate the Pipe-in-Pipe (PiP) model for piles, a computationally efficient model
for piled foundations based on the homonymic model for vibrations from underground railways. The
models are found to be in good agreement, which offers great perspectives to use the PiP model as an
engineering tool.
The influence of adjacent piles on the response of a certain pile is investigated by means of a power
flow analysis. It will be demonstrated that the effect is strongly dependent on the relative positions
of the piles compared to the position of the load applied. Moreover, a tendency to wave scattering is
revealed when the wavelength approaches the distance between piles and load.
Ultimately, the response of piled foundations to underground railway induced loadings is investigated.
Uncoupling of source (railway track) and receiver (piled foundations) is assumed, resulting in a two-step approach. The model is once more used to validate the PiP model for piles. Several aspects, such as the effect of the foundation design, the contribution of horizontal and rotational motion, the importance of pile-soil-pile interactions and the isolation performance of base isolation are examined. Results suggest that steel springs are preferred to rubber bearings, as the isolation frequency can be lowered more significantly. Moreover, it will become clear that the current boundary element model has the ability to reveal the complexity of the situation, which cannot be achieved by means of simplified
models.