Response of 0.6 m Cast-in-Steel-Shell Pile in Liquefied Soil under Lateral Loading

This paper presents results from a full-scale lateral load test on a 0.6  m cast-in-steel-shell (CISS) pile in sand liquefied by controlled blasting. Lateral loads were applied by a hydraulic actuator to simulate seismic inertial forces. The CISS pile was instrumented to provide the data necessary for back calculating lateral soil resistance and displacement. Details of the pile instrumentation and testing procedure are described. The back-calculated soil resistance and displacement are presented as p–y curves and compared to static sand p–y curves. Results from three simplified analyses are presented, where liquefied soil resistance was accounted for by modifying standard static p–y curves, and compared to measured test results. Limitations of the simplified methods are discussed. Test results show the blast induced liquefied sand did not provide resistance to lateral pile movement at displacements up to 50  mm. At displacements of sufficient magnitude, a phase transformation in the sand occurred resulting in a reduction in pore water pressure, and increased lateral soil resistance. The shape of the backcalculated p–y curves for liquefied sand is significantly different from the shape of standard p–y curves. As a result, the modified standard p–y curves do not adequately model the liquefied soil response. Consequently, results from simplified analyses vary from conservative to non-conservative as displacement levels increase.