Abstract: This paper presents a comparative analysis of foundation design schemes and corresponding cost implications across different design stages for the Shantou Detention Center service-facility project. In the preliminary design stage, a composite foundation scheme was adopted, in which cement-mixed columns were used for localized ground improvement, followed by a shallow-foundation system. During the construction-drawing stage, however, adjustments to the building layout resulted in changes to the underlying geological conditions, necessitating a redesign to a percussive bored cast-in-place pile foundation. The study highlights that shifts in building location can alter subsurface conditions, requiring timely analytical reassessment and modification of the foundation system. Given the influence of multiple factors—including government management requirements, evolving user needs, and actual construction constraints—engineering technical conditions often change over the course of a project. Project management should therefore be based on real-time engineering conditions rather than rigidly adhering to the principle that later-stage design costs must not exceed earlier-stage budget limits. The findings provide a useful reference for similar engineering projects.

Key words: Ground Improvement, Cement Mixed Soil Column, Composite Foundation, Shallow Foundation, Percussive Bored Cast-In-Place Piles, Post-Grouted Pile Foundations