# Digital Twin-Driven Stability Optimization Framework for Large Underground Caverns
## 2 Digital Twin Framework for Real-Time Monitoring and Optimization of Underground Caverns
### Digital Twin Modules  
Figure 2 shows the digital twin modules applied in the proposed real-time monitoring of convergence and stability optimization of underground caverns. These features and functions in the virtual and real worlds are necessary to simulate and replicate the behavior in the real world. Figure 1: Five-dimensional digital twin framework. Figure 2: Digital twin modules applied in optimization. The structure DT simulates the location, geometry, and design layout with all the salient features of an underground cavern. The geometric design and location are based on the virtual iterative numerical analysis. It assists the guide for real structure construction for the desired underground cavern facility and corrects itself with feedback from the physical identities during construction. The geology DT replicates detailed geological information and records its physical attributes. It provides structural geological information including rock type, Q-value, bedding planes, dip angle, dip direction, joint set, infilling, and discontinuity spacing. The geological information is updated throughout the construction process. It begins with borehole data, where the geological model is developed by interpolation, and later, during construction, geological information is updated with feedback. This information from this module influences stress distribution, deformation behavior, failure mechanisms, and support system design, enabling accurate predictive modeling and real-time adjustments for enhanced structural stability. The recorded information is the key to optimizing the convergence of an underground structure to enhance real-time monitoring, enabling proactive adjustments for stability and efficiency. The material DT simulates the records of the actual rock mass properties integrated into the geological model and replicates the mechanical behavior and structural response of the rock. This information is gathered through an extensive laboratory testing program to have the material properties of natural intact rock and rock mass parameters. The values were obtained from tests conducted in the laboratory on small specimens of rock. They must be adjusted to full-scale conditions to represent the overall rock mass conditions. This module plays a crucial role in realistic deformation modeling, predictive accuracy, and adaptive stability control in digital twins by defining the mechanical behavior of rock. The behavior DT is a set of simulation models used to evaluate and simulate the rock's response to all kinds of excavation activities and rock support systems. FEM analysis is used to estimate stresses and deformations. In the DT module, convergence simulation models are developed based on pre-excavation information in the initial design phase. During the excavation phase, more detailed simulation models are updated on actual excavation, and actual convergence information and feedback are provided to the DT system for the optimization process. The feedback during excavation explains the changing states of stress while excavating the parts as the excavation is deepened or different sections of underground space are excavated. The performance DT provides analysis and duplicates the performance of the rock support system to replicate the excavation stress in a virtual environment. Stress analysis is carried out in the design stage to design the rock to keep the convergence and deformation within the design limit. The sequence of support installation is also matched with the sequence of excavation to provide adequate support without the risk of overstressing the support elements. During construction, performance is analyzed for additional support measures based on the actual condition and feedback from the behavior DT module. The real-environment DT simulates the whole construction process and its elements. It not only replicates the real external environment of the geometric data with construction sequences but also integrates the instrumentation installation plans.