# Voxel-Based Digital Twin Framework for Earthwork Construction
## 4 Implementation of the Proposed System  
This study used excavation sites as examples to verify the developed framework and system capabilities for earthwork construction. The system architecture is shown in Figure 7. First, it collects all related information, including surface terrain data, subsurface information, design BIM models, equipment data, and scans collected during the construction stage, to represent the current state of information. All these data are converted into a virtual platform in the next phase to create the earthwork digital replica, which can update the digital models when new data from the physical twin is available. The as-is condition data are converted into a graphical simulation environment for model-equipment interaction. Moreover, the as-planned and as-built data are continuously compared for progress monitoring, facilitating practitioners with visual and quantitative insights into progress.  
The system is implemented using commercial tools such as Autodesk Civil 3D, Rhino 3D, and Unity 3D. For instance, the ground, geotechnical model, and design model are developed using Autodesk Civil 3D 2023, while Rhino 3D version 8 is used for the design voxelization and integration of all models to achieve the as-planned model. The point cloud data achieved during the construction stage, after preprocessing in CloudCompare, is converted into a TIN surface in Autodesk Civil 3D, representing the current state of construction, and later integrated with the as-planned model in Rhino 3D. The as-planned model is updated accordingly, and progress is visualized and quantified inside Rhino 3D. Meanwhile, the as-planned model in the preconstruction stage or as-is condition  
Figure 7: Demonstration steps of the proposed system.  
information during any construction is linked with Unity 3D for graphical simulation and model-equipment interaction. Also, the C# scripts are designed within Unity 3D for model-equipment interaction. All these models--adopted from the physical twin through data acquisition techniques--are processed, virtualized, simulated, analyzed, and updated in near-real time whenever new data is available.  
Considering the implementation scenarios of the proposed digital twin system, two different case studies were selected. A building pad excavation project was used for the implementation of the graphical simulation environment using the digital twin data. Moreover, a trench excavation site was used to implement progress monitoring. However, the study framework is general and can be applied to all earthwork cases. The selected case studies, a building pad and trench, represent two of the most commonly encountered earthwork conditions in infrastructure and site development projects. The building pad scenario is typical of large-scale cut-and-fill operations requiring broad volumetric balancing and ground preparation for structural foundations. On the other hand, the trench excavation is representative of narrower and linear excavations frequently used for utility installations or road excavation, making it suitable for assessing detailed boundary conditions and model-equipment interaction at a fine resolution. These two case studies together offer balanced and realistic representations of earthwork conditions that span different operational requirements and geometric constraints.