Ultimate Capacity of Short Piles in Clay under Lateral Loading-Paper

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The study uses three-dimensional finite-element limit analysis (FELA) to estimate the ultimate lateral capacity of rigid, fixed-head short piles in homogeneous, undrained clay. It examines pile aspect ratios (L/D) from 0.5 to 6, smooth and rough pile–soil interfaces, interface tension capacity, and the normalized soil-weight parameter γ′D/su. Adaptive remeshing produces lower- and upper-bound collapse loads, generally within about 10% of each other.<br /><br />With unlimited interface tension, soil weight does not affect capacity. Rough piles carry about 25–30% more load than smooth piles. Failure transitions from shallow wedge mechanisms for short piles to flow-round mechanisms at depth for longer piles. The depth-dependent lateral resistance factor, Np, rises rapidly over approximately the first pile diameter, reaches a steady value below about 2D, and changes near the pile tip as resistance from the soil beneath it becomes significant.<br /><br />When the interface cannot sustain tension, a gap may form behind the pile. Capacity then depends strongly on γ′D/su: increasing soil weight generally suppresses the gap, promotes flow-round resistance, and raises capacity toward—but not beyond—the unlimited-tension result. For weightless soil, no-tension resistance can be much lower than full-tension resistance. The study also finds that the Murff and Hamilton method, which adds soil-weight effects to a weightless-soil solution, can substantially overestimate local resistance at higher γ′D/su unless an appropriate flow-round cutoff is applied.<br /><br />The FELA results clarify how soil weight, interface conditions, and pile geometry govern capacity and failure mechanisms. They also provide depth-dependent Np profiles that can inform theoretically grounded p–y curves for pile–soil interaction analyses.

Keywords

finite-element limit analysis

lateral capacity

rigid fixed-head piles

undrained clay

pile-soil interface

soil weight parameter

flow-round mechanism

shallow wedge mechanism

lateral resistance factor

p-y curves