Design and Validation of an Integrated CAD-to-5D BIM Process for Underground Utilities

Underground utility projects still rely on 2D drawings, which fragments geometry, process, and cost information and raises the barrier to BIM adoption. There is a need for a practical method that preserves existing CAD workflows while achieving integrated, higher-dimensional management. This study proposes a unified framework that converts 2D CAD into 3D BIM and automatically combines work and cost information to produce 5D outputs in a single, interoperable model. The approach aims to maintain data continuity from design to construction, reduce manual modeling effort, and lower adoption costs. A prototype system and viewer were developed to validate the end-to-end flow and to confirm that geometry, schedule, and cost can be reviewed together. The framework offers a feasible path for digital transformation in underground utilities and can be extended toward 6D and 7D for performance and operations management.