Surrounding rock deterioration and large deformation have always been a significant difficulty in designing and constructing tunnels in soft rock. The key lies in real-time perception and quantitative assessment of the damaged area around the tunnel. An in situ microseismic (MS) monitoring system is established in the plateau soft tock tunnel. This technique facilitates spatiotemporal monitoring of the rock mass's fracturing expansion and squeezing deformation, which agree well with field convergence deformation results. The formation mechanisms of progressive failure evolution of soft rock tunnels were discussed and analyzed with MS data and numerical results. The results demonstrate that: (1) Localized stress concentration and layered rock result in significant asymmetry in micro-fractures propagation in the tunnel radial section. As excavation continues, the fracture extension area extends into the deep surrounding rockmass on the east side affected by the weak bedding; (2) Tunnel excavation and longterm deformation can induce tensile shear action on the rock mass, vertical tension fractures (account for 45%) exist in deep rockmass, which play a crucial role in controlling the macroscopic failure of surrounding rock; and (3) Based on the radiated MS energy, a three-dimensional model was created to visualize the damage zone of the tunnel surrounding rock. The model depicted varying degrees of damage, and three high damage zones were identified. Generally, the depth of high damage zone ranged from 4 m to 12 m. This study may be a valuable reference for the warning and controlling of large deformations in similar projects. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

To investigate the long-term stability of deep rocks, a three-dimensional (3D) time-dependent model that accounts for excavation-induced damage and complex stress state is developed. This model comprises three main components: a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state, a quantitative relationship between critical irreversible deformation and complex stress state, and evolution characteristics of strength parameters. The proposed model is implemented in a self-developed numerical code, i.e. CASRock. The reliability of the model is validated through experiments. It is indicated that the time-dependent fracturing potential index (xTFPI) at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage. The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress, thereby highlighting the 3D stress-dependent characteristic of the model. Finally, the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Excavation-induced disturbances in deep tunnels will lead to deterioration of rock properties and formation of excavation damaged zone (EDZ). This excavation damage effect may affect the potential rockburst pit depth. Taking two diversion tunnels of Jinping II hydropower station for example, the relationship between rockburst pit depth and excavation damage effect is first surveyed. The results indicate that the rockburst pit depth in tunnels with severe damage to rock masses is relatively large. Subsequently, the excavation-induced damage effect is characterized by disturbance factor D based on the Hoek-Brown criterion and wave velocity method. It is found that the EDZ could be further divided into a high-damage zone (HDZ) with D 1/4 1 and weak-damage zone (WDZ), and D decays from one to zero linearly. For this, a quantitative evaluation method for potential rockburst pit depth is established by presenting a three-element rockburst criterion considering rock strength, geostress and disturbance factor. The evaluation results obtained by this method match well with actual observations. In addition, the weakening of rock mass strength promotes the formation and expansion of potential rockburst pits. The potential rockburst pit depth is positively correlated with HDZ and WDZ depths, and the HDZ depth has a significant contribution to the potential rockburst pit depth. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Excavation of underground caverns, such as mountain tunnels and energy-storage caverns, may cause the damages to the surrounding rock as a result of the stress redistribution. In this influenced zone, new cracks and discontinuities are created or propagate in the rock mass. Therefore, it is effective to measure and evaluate the acoustic emission (AE) events generated by the rocks, which is a small elastic vibration, and permeability change. The authors have developed a long -term measurement device that incorporates an optical AE (O-AE) sensor, an optical pore pressure sensor, and an optical temperature sensor in a single multi -optical measurement probe (MOP). Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high -level radioactive waste (HLW) deep geological disposal technology. In a high -level radioactive disposal project, one of the challenges is the development of methods for long -term monitoring of rock mass behavior. Therefore, in January 2014, the long -term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center. The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation. In addition, hydraulic conductivity increased by 2-4 orders of magnitude. Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures. Based on this, a conceptual model is developed to represent the excavation damaged zone (EDZ), which contributes to the safe geological disposal of radioactive waste. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

In order to evaluate the performance of deep geological disposal of radioactive waste, an underground research laboratory (URL) was constructed by Andra in the Callovo-Oxfordian (COx) claystone formation at the Meuse/Haute-Marne (MHM). The construction of URL induced the excavation damage of host formations, and the ventilation in the galleries desaturated the host formation close to the gallery wall. Moreover, it is expected that the mechanical behaviour of COx claystone is time -dependent. This study presents a constitutive model developed to describe the viscoplastic behaviour of unsaturated and damaged COx claystone. In this model, the unsaturation effect is considered by adopting the Bishop effective stress and the van Genuchten (VG) water retention model. In terms of the viscoplastic behaviour, the nonstationary flow surface (NSFS) theory for unsaturated soils is used with consideration of the coupled effects of strain rate and suction on the yield stress. A progressive hardening law is adopted. Meanwhile, a non -associated flow rule is used, which is similar to that in Barcelona basic model (BBM). In addition, to describe the damage effect induced by suction change and viscoplastic loading, a damage function is defined based on the crack volume proportion. This damage function contains two variables: unsaturated effective stress and viscoplastic volumetric strain, with the related parameters determined based on the mercury intrusion porosimetry (MIP) tests. For the model validation, different tests on COx claystone under different loading paths are simulated. Comparisons between experimental and simulated results indicated that the present model is able to well describe the viscoplastic behaviour of damaged COx claystone, including swelling/shrinkage, triaxial extension and compression, and triaxial creep. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).