# Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics
## 2 An Overview of Published Articles
Additionally, the calibration procedure of the models based on laboratory tests is described. An application example is provided to demonstrate the effectiveness of bonded-block models in analyzing underground excavation problems. The example utilizes a simple bonded-block model comprising rigid blocks and a bilinear softening contact model. The simulation results illustrate the model's ability to accurately reproduce observed failure modes, including block fractures. Overall, the paper highlights the potential of bonded-block models as a powerful tool in the numerical simulation of rock failure processes. \"Analysis of Deformations of the Tunnel Excavation Face via Simplified Calculation Methods\" by [PERSON] and [PERSON] (contribution 7) focuses on ensuring the stability of the excavation face during tunnel construction, which is essential for ensuring the safety of workers and the progress of the project. This study utilizes simplified numerical calculation methods and analytical techniques to analyze the stability conditions of the tunneling face, particularly focusing on the extrusion of the face as an indicator of the mechanical behavior of the rock ahead. One notable aspect is the comparison between the numerical method and the hemispherical method, demonstrating the reliability of the latter for such analyses. By conducting an extensive parametric analysis, considering various geometric and geomechanical parameters typical of tunnel excavation in weak rock, this study determines the extent of face extrusion and its dependence on these parameters. Moreover, comparing the extrusion values obtained from calculations with established limit values from the scientific literature enables a rapid assessment of face stability. Additionally, a specific investigation of the role of pressure applied to the face provides insights into defining the intensity of main stabilization systems, such as TBM (Tunnel Boring Machine) thrust and longitudinal fiberglass bolts, to prevent face collapse. Overall, this study contributes to enhancing our understanding of the mechanical behavior of tunnel faces in weak rock conditions and provides insights for optimizing stability assessments and implementing appropriate stabilization measures during tunnel excavation projects. \"Numerical Modeling and Back-Analysis Approach on a Monitored Underground Cavern for the Extraction of Marble for Ornamental Uses\" by [PERSON] et al. ((contribution 8) focuses on the significance of the Cava Madre of Candoglia, an underground rock cavern in northwest Italy, which is renowned for its historical importance and as a source of marble used in the ongoing renovation of the Milan Cathedral. As the cavern expanded over time, significant horizontal stresses necessitated the construction of robust support structures to stabilize the side walls. To ensure ongoing safety and stability, a sophisticated monitoring system is employed. To enhance the reliability of geomechanical characterization and the numerical model used to analyze stress and strain behavior within the cavern, the researchers developed a back-analysis approach. This involved calibrating two key geomechanical parameters: the elastic modulus of the marble at the problem scale and the lateral thrust coefficient at rest (k0), which had significant uncertainty. By refining these parameters through back-analysis, the accuracy of the numerical model was improved, leading to a more precise understanding of the cavern's behavior. The refined numerical model facilitated a comprehensive examination of the support and stabilization structures within the cavern's walls. This analysis enabled the verification of the effectiveness of these structures and informed careful planning for future mining activities to continue extracting marble from the existing bench. By leveraging insights gained from the back-analysis and numerical modeling, the project can proceed with confidence, ensuring the sustainable exploitation of the valuable marble resource while prioritizing safety and stability.