Stiffness of piles in liquefiable soils

This paper describes the results of an investigation of the dynamic stiffness of pile foundations in liquefiable soils. Such soils frequently exist near bodies of water where bridges are required. Because potentially liquefiable soils are generally weak and compressible even under static conditions, bridges founded on them are usually supported on pile foundations. During earthquake shaking, the excess porewater pressure that builds up in liquefiable soils influences both the seismic response of the soil deposit itself, and also the local interaction with any foundations that extend through the liquefiable soil. These phenomena can strongly influence the stiffness of pile foundations in liquefiable soils during earthquakes, and need to be accounted for if accurate evaluations of pile stiffness are to be obtained. In this work, tools and procedures were developed for evaluation of the stiffness of pile foundations in liquefiable soils during earthquakes.