A Study in Extreme Event Large Displacement Analysis of Large Diameter Piles-Paper

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The paper presents a three-dimensional finite-difference method for analyzing large-diameter shafts under extreme lateral loading, including landslides, lateral spreading, and fault rupture. Conventional beam-on-elastic-foundation methods treat soil response locally and are poorly suited to large displacements, where the shaft and surrounding soil influence one another. The proposed method models soil, rock, and concrete as continua with nonlinear, stress-dependent behavior and strain softening. Reinforcing bars and steel casing are represented separately, with interfaces that allow slip. This approach can capture cracking and yielding, soil gapping and displacement, shaft rotation, and complex three-dimensional interaction.<br /><br />The method was compared with three full-scale lateral pile tests: a 0.3 m shaft in weakly cemented sand, a 1.0 m drilled shaft in dense sand, and a 1.0 m shaft in loose-to-medium-dense sand. Simulations generally reproduced the measured responses. The first case also showed that modeling soil strain softening and stress-dependent stiffness matters: omitting softening overestimated ultimate resistance, while constant stiffness produced less realistic initial behavior.<br /><br />The authors conclude that the method is promising for large-displacement problems and may remain robust for soil movements of several metres, although the validation tests themselves involved much smaller displacements. Predictions are most sensitive to concrete stiffness and tensile strength, and to realistic soil softening and brittle concrete behavior; they are moderately sensitive to steel properties. Further validation against landslide and lateral-spreading cases is needed.

Keywords

finite-difference method

three-dimensional analysis

large-diameter shafts

lateral loading

soil-structure interaction

nonlinear soil behavior

strain softening

full-scale pile tests

concrete cracking

steel casing