During precast beam yard construction on soft ground, prestress tensioning-induced camber transforms the initially uniform load distribution into eccentric concentrated loads at the beam ends, thereby posing risks to foundation stability and geometric accuracy. This study investigates the mechanical responses of natural ground, single-pile reinforcement, and double-pile reinforcement under tension loading through field monitoring and numerical simulations based on a Hangzhou–Ningbo Expressway project. The results show that single-pile reinforcement exhibits a typical point-support behavior, characterized by significant stress concentration at the pile head, a pile–soil stress ratio ranging from 3.0 to 4.0, and a coefficient of variation in base pressure reaching 0.81. In contrast, the double-pile scheme enables load redistribution through a line-support mechanism along the beam length, improving stress uniformity and reducing the coefficient of variation to 0.62. Orthogonal test-based sensitivity analysis further identifies pile diameter and cushion thickness as the dominant factors influencing composite ground. performance. This study clarifies the differences in load-transfer mechanisms among various pile arrangements under tension loading and provides a theoretical basis for the optimized design of casting bed foundations for precast beam yards in soft soil regions.