The mechanical behavior of flexible pipes buried in sandy soils is significantly influenced by the dilatancy of sand—a critical factor in pipe–soil interaction that governs load transfer mechanisms and soil deformation behavior. This study investigates the role of dilatancy in soil behavior and pipe deformation under. This paper examines the behavior of backfill material, specifically sand, in both elastic and plastic states, and explores how dilation influences pipe load and deformation. A computational analysis integrating traditional methods, such as Iowa’s equation, with stress-dilatancy theory and critical state soil mechanics is presented. The results highlight the importance of accounting for dilatancy in design models and suggest future research directions in pipeline–soil interaction.