# 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 Methodology
The accuracy of this optimization process is ensured through a continuous verification process that integrates real-time monitoring data from installed sensors with the virtual model. During construction, the measured deformations are constantly compared against FEM/FDM predictions through the digital twin framework. As excavation progresses and new geological data become available, the system automatically evaluates whether actual convergence remains within the predefined trigger levels (Section 2.5). When thresholds are approached or exceeded, the DT initiates the iterative recalibration of support parameters--including bolt spacing, shotcrete thickness, and anchor configurations--to maintain structural safety. Based on structural geology, rock support design and excavation stages are virtually analyzed to understand the deformation behavior and long-term stability. In the rock support design virtual simulation, the type of rock support, dimensions, material, the thickness of shotcrete, and the angle and pattern of rock anchors are finalized based on simulation results, providing better stability. This process creates a closed feedback loop where field measurements continuously validate and refine the virtual model, ensuring that the digital twin remains an accurate representation of physical conditions throughout the project lifecycle. This step also reviews and verifies the location and geometric design layout, and if any necessary modifications are required, the feedback is input back into Step 2. During construction, as-built information is provided to re-evaluate the structure's stability and deformation behavior. If any necessary action needs to be taken to redesign the rock support, it provides the rock support design update. After excavation and rock support or in the operation phase, the sensors provide real-time feedback on the actual deformation behavior of the underground facility. This feedback is compared with the virtual design, simulations are corrected in accordance with the real deformation, and rock support is re-evaluated. _Step 4:_ BIM-based detailed design and construction simulation provide detailed digital geometric and semantic descriptions of construction details, along with virtual construction sequences. This step facilitates effective information storage, meaningful data sharing, and collaborative design for multiple experts from different domains in complex and huge underground complexes. The parametric geometric model provides a detailed design visualization of geometric data of all the components in a three-dimensional space. It provides the detailed information of excavation, rock support, and monitoring instrumentation detailed design. It includes excavation geometry, phased excavation plans, and geotechnical data. The rock support design specifies systems like rock bolts, shotcrete, and steel ribs, integrated with stress analysis and material properties. Monitoring instrumentation plans detail device locations. _Step 5:_ After the detailed design is completed, the actual construction of the underground cavern is commenced in the physical world based on all the current information from the virtual world. In the actual construction process, the excavation commences with the widening of the pilot tunnel constructed for the feasibility study in Step 1, which is later widened to achieve the full width of the crown. The rock mass information is collected and mapped on geological sheets to prepare as-built geological details as excavation progresses. The excavation should be carried out in benches to ensure safety, stability, and the efficient management of the construction process. Excavating in benches allows for the controlled removal of material in stages, reducing the risk of collapse by maintaining the stability of the surrounding rock. This method also provided better access for installing rock support systems.