<p>Loess had a loose structure, well-developed vertical fissures, and notable macro-pores, and was widely distributed globally. Under the combined effects of overlying load and rainfall infiltration, it was prone to significant collapsible settlement, posing serious challenges to infrastructure construction. Pile foundations, serving as a key engineering solution for construction in collapsible soil layers, were traditionally designed based on saturated soil mechanics theory. This approach failed to fully account for the influence of matric suction and collapsible settlement under unsaturated conditions on the load transfer mechanism of piles. Through laboratory tests, a prediction model of loess collapsible deformation upon wetting and under surcharge was initially proposed, extending the unsaturated soil mechanics concepts. The traditional load transfer curve model was then modified to extend its application to collapsible loess by further considering the contribution of matric suction to the pile shaft friction. To evaluate the feasibility of the proposed modified load transfer method, large-scale model pile infiltration tests were conducted. The results demonstrated that water infiltration significantly degraded the mechanical properties of the loess due to reduction in matric suction and the occurrence of collapsible deformation, resulting in a notable decrease in the bearing capacity of the pile foundations. The test results showed close agreement with the predictions, confirming the feasibility of the modified model. Its computation program was concise and involved only a limited number of soil index and mechanical properties, making this method easy to apply in engineering practice.</p>