Time-dependent response of a loaded pile under excavation- and dewatering-induced non-Darcy reverse consolidation

Excavation and dewatering around existing service-loaded piles alter the hydromechanical state of saturated soft clay and the shaft length available for load transfer. Reduced-order load-transfer analyses often simplify excavation-induced soil response and do not explicitly resolve reverse consolidation, loading-history effects, or progressive loss of pile-soil contact. This study develops a time-domain sequential one-way coupled framework in which the soil response is first resolved and then transferred to a path-dependent pile model without pile-to-soil feedback. The formulation combines an equivalent-preloading-history fractional Merchant model, Hansbo non-Darcy flow, construction-dependent drainage boundaries, excavation-induced contact removal, and unilateral pile-toe contact, while retaining the finite preloading history throughout construction. It is intended for cases where construction-induced soil response dominates pile-induced disturbance. The formulation is assessed through constitutive comparisons, independent Darcy-limit solutions, a published reverse consolidation benchmark, calibrated pile-component comparisons, and an independent three-dimensional numerical comparison. Excavation depth primarily governs soil rebound and redistribution of pile axial force and shaft resistance, whereas drainage conditions mainly affect transient evolution. Toe separation shifts sustained service load from the pile base toward the shaft, promoting shaft-resistance reversal and tensile axial-force development. Dewatering suppresses excavation-induced rebound. The identified constitutive parameters vary markedly with unloading stress window, requiring stress-history-consistent calibration for site-specific prediction.