Strain Wedge Model for Piles/Shafts in Liquefied Soil

This paper describes the calibration of the Strain Wedge Model (SWM) response using the Treasure Island test measured data. The SWM, initially developed to assess the relationship between one-dimensional beam on elastic foundation (BEF) or so called "p-y" curve behavior and three dimensional soil pile interaction, has been extended to include laterally loaded piles/shafts in liquefiable soil. Because the SWM relies on the undrained stress-strain characterization of the soil as occurs in the triaxial test, it is capable of treating one or more layers of soils that experience limited or full liquefaction. This paper provides a methodology to assess the post-liquefaction response of an isolated pile/shaft in sand under an applied pile/shaft head load/moment combination assuming undrained conditions in the sand. The degradation in soil strength due to the free-field excess porewater (u_xs,ff), generated by the earthquake that results in developing or full liquefaction, is considered along with the near-field excess porewater pressure (u_{xs, nf}) generated by lateral loading from the superstructure. The tests include lateral load testing of 1- and 3-foot diameter piles/shafts at Treasure Island in San Francisco Bay Area in as-is and blast induced liquefied conditions.