In general, modern construction projects are characterized by large construction scale, high construction difficulty, and complex project management and data information analysis. Hence, various technologies should be fused and integrated to comprehensively and effectively manage the project construction. In this paper, a multi-source heterogeneous data fusion technology, which combined building information modelling (BIM), geographic information system (GIS), and Internet of Things (IoT) (BIM + GIS + IoT Multi-Source Heterogenous Data Fusion), was systematically explored to achieve a total factor, data sensing, and heterogeneous fusion concept. Then, the BIM + GIS scene-based 3D modelling technology was discussed from three aspects: total factor information 3D modelling, model tiled loading, and ultra-large model lightweight processing. With a tunnel construction project combined, a tunnels Internet-based construction management platform was developed on the basis of BIM + GIS + IoT multi-source heterogeneous production data fusion, thereby realizing the organic integration of virtual model information and total factor production information. Furthermore, the platform provided the capability of monitoring core indexes such as gas, geology, personnel, and progress involved in the tunnel construction, which facilitated the dynamic visual management of the construction process and enhanced management efficiency.

In view of tunnel engineering characteristics, such as "high ground stress, high gas concentration, many fault-fracture zones/unfavorable geological conditions/groundwater corrosiveness types and large buried depth," research on key tunnel digital construction technologies was performed to integrate engineering construction, geological investigation report and geographic information 3D models into 3D visual data information. In the research, large BIM models are lightened with the mass cutting method based on the combination of BIM and GIS of the Cesium engine. A heterogeneous model integration method is proposed to convert BIM into FBX format. Then FBX is converted into 3DTiles standard format suitable for Cesium engine, thereby combining BIM and GIS technologies. In the end, a B/S architecture-based case is demonstrated, which solves the tunnel safety warning problem by realizing a visual tunnel safety warning. Site data is loaded in the full element 3D model in a real-time manner with the combination of Cesium engine and tile & lightweight technologies to achieve back-end "data middle platform" integrated operation and 1:1 mapping of front-end "digital construction site" and "real construction site," which has reference value to the application of BIM + GIS technologies in the railway tunnel industry.