Multi-Source Data Fusion and Multi-Scale Constraints for Continuous Surface-Subsurface 3D Geological Modeling

The inherent uncertainty of subsurface geological conditions remains a primary challenge in underground spatial planning and rock engineering. The rationality of engineering design is fundamentally dictated by the spatial distribution and continuity of geological structures. However, in complex environments—characterized by intense tectonic fracturing or rapid lithological transitions—traditional 2D projections often fail to capture the anisotropic nature and spatial evolutionary trends of the rock mass, leading to significant interpretative gaps. Discrepancies between predicted and encountered geology frequently stem from a 2D conceptual framework that oversimplifies the 3D connectivity of fault planes, shear zones, and joint sets. This study addresses these limitations by utilizing the Zhaishan Tunnel system in Kinmen, characterized by its granitic basement, as a research platform. By integrating UAV LiDAR, Terrestrial Laser Scanning (TLS), and SLAM technologies, we established a high-resolution 3D spatial database that bridges the gap between surface and subsurface geological data. The core research focus is the development of a workflow for continuous surface-subsurface 3D geological modeling. By incorporating surface topography, outcrop mapping, and in-situ structural measurements into a unified 3D coordinate system, the study employs multi-scale data constraints to enhance the reliability of geological interpretations. Macro-scale surface terrain data are utilized to constrain the meso-scale structural interpretations within the tunnel, ensuring that the model maintains structural consistency across different depths. The significance of this research lies in transforming geological outputs from static, post-survey records into dynamic, 3D interpretative engines. This approach allows for the visualization of discontinuity extensions in three dimensions, providing a data-driven framework for anticipating geological hazards. Ultimately, this shift ensures that geological interpretations are no longer fragmented, providing a high-integrity information base for modern underground space development and structural stability analysis.