An experimental apparatus was developed to investigate the behaviour of vertically loaded free-head piles in sand undergoing lateral soil movement (wf). A large number of tests have been conducted to date. Presented here are 14 typical model pile tests concerning two diameters, two vertical pile loading levels, and varying sliding depths with the movement wf driven by a triangular loading block. Results are provided for driving force as well as for induced shear force (T), bending moment (M), and deflection ( y) along the piles with wf / normalized sliding depth. The tests enable simple expressions to be proposed, drawn from the theory for a laterally loaded pile. The new expressions well capture the evolution of M, T, and y with soil movement observed in current model tests, and the three to five times difference in maximum bending moment (Mmax) from the two modes of loading. They further offer a good estimate of Mmax for eight in situ pile tests and one centrifuge test pile. The study quantifies the sliding resistance offered by a pile for the given wf profiles, pile location (relative to the boundary), and vertical load. It establishes the linear correlation between the maximum thrust (resistance T) and Mmax, regardless of the magnitudes of wf.

The traditional approaches for evaluating the stability of slopes or earth dams subjected to water drawdown are performed under plane-strain two-dimensional (2D) condition. Three-dimensional (3D) effect is neglected in assessment of the safety of a slope limited by rigid structures or a dam constrained by a narrow valley. Based on the kinematic approach of limit analysis, a 3D rotational failure mechanism is adopted here to investigate the influence of water drawdown on stability of 3D slopes. Several stability charts are presented to conveniently estimate the safety factor of 3D slopes under four different types of drawdown processes. An example is given to demonstrate the difference in the safety factors obtained from 2D and 3D analyses. When a slope is constrained to a large width (the ratio of the width to the height B/H ≥ 10.0), the 3D effect can be neglected and the plane-strain analysis is appropriate to assess its safety.

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