This study presents the classification and prediction of severity for brittle rock failure, focusing on failure behaviors and excessive determination based on damage depth. The research utilizes extensive field survey data from the Shuangjiangkou Hydropower Station and previous research findings. Based on field surveys and previous studies, four types of brittle rock failure with different failure mechanisms are classified, and then a prediction method is proposed. This method incorporates two variables, i.e. Kv (modified rock mass integrity coefficient) and GSI (geological strength index). The prediction method is applied to the first layer excavation of the powerhouse cavern of Shuangjiangkou Hydropower Station. The results show that the predicted brittle rock failure area agrees with the actual failure area, demonstrating the method's applicability. Next, it extends to investigate brittle rock failure in two locations. The first is the k0+890 m of the traffic cavern, and the second one is at K0-64 m of the main powerhouse. The criterion-based prediction indicates a severity brittle rock failure in the K0+890 m section, and a moderate brittle rock failure in the K0-64 m section, which agrees with the actual occurrence of brittle rock failure in the field. The understanding and application of the prediction method using Kv and GSI are vital for implementing a comprehensive brittle rock failure prediction process in geological engineering. To validate the adaptability of this criterion across diverse tunnel projects, a rigorous verification process using statistical findings was conducted. The assessment outcomes demonstrate high accuracy for various tunnel projects, allowing establishment of the correlations that enable valuable conclusions regarding brittle rock failure occurrence. Further validation and refinement through field and laboratory testing, as well as simulations, can broaden the contribution of this method to safer and more resilient underground construction. (c) 2024 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 license (http://creativecommons.org/licenses/by/4.0/).

Accurate prediction of rockburst proneness is one of challenges for assessing the rockburst risk and selecting effective control measures. This study aims to assess rockburst proneness by considering the energy characteristics and qualitative information during rock failure. Several representative rock types in cylindrical and cuboidal sample shapes were tested under uniaxial compression conditions and the failure progress was detected by a high-speed camera. The far-field ejection mass ratio (FEMR) was determined considering the qualitative failure information of the rock samples. The peak-strength energy impact index and the residual elastic energy index were used to quantitatively evaluate the rockburst proneness of both cylindrical and cuboidal samples. Further, the performance of these two indices was analyzed by comparing their estimates with the FEMR. The results show that the accuracy of the residual elastic energy index is significantly higher than that of the peak-strength energy impact index. The residual elastic energy index and the FEMR are in good agreement for both cylindrical and cuboidal rock materials. This is because these two indices can essentially reflect the common energy release mechanism characterized by the mass, ejection velocity, and ejection distance of rock fragments. It suggests that both the FEMR and the residual elastic energy index can be used to accurately measure the rockburst proneness of cylindrical and cuboidal samples based on uniaxial compression test. (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/).