The accurate selection of rock mass mechanical parameters is crucial for the support design of underground caverns and the evaluation of their overall stability. Longyou Grottoes, known as the "Ninth Wonder of the World," have suffered extensive damage in some caverns due to weathering, aqueous solution erosion, human activities, and other factors. After a critical review of the deficiencies in the Hoek–Brown strength criterion and its existing modifications, this study introduces correction coefficients (Km) and (Ks) that consider both the degree of rock mass disturbance and the nonlinearity of the Hoek–Brown strength criterion. A more reasonable method for determining the empirical parameters mb and s is proposed, and an improved formula for the Hoek–Brown strength criterion is thereby derived. Based on this improved empirical formula of the Hoek–Brown strength criterion, more reasonable rock mass mechanical parameters for the ancient cavern group are obtained. Additionally, a numerical model of the Cuiguangyan ancient cavern group is established using the "RHINO-GRIDDLE-FLAC3D" combined approach, and the strength reduction method is employed to predict and analyze the failure characteristics of the ancient cavern group. The research results are as follows: (1) The corrected Km and Ks are characterized by the integrity coefficient Kv, which not only reflects the degree of rock mass disturbance but also conforms to the nonlinearity of the Hoek–Brown strength criterion, thus overcoming the limitations of previous improved formulas. (2) Using the strength reduction method, it is found that the failure process of the ancient cavern group can be roughly divided into three stages: When the reduction factor ranges from 1.0 to 1.5, the vertical displacement and stress of the rock mass exhibit an approximately linear relationship with the reduction factor. When the reduction factor is between 1.75 and 2.25, a large number of new fractures or cracks appear inside the rock mass; at this stage, the plastic zone gradually transforms into a loosened zone, the entire cavern is in a critically unstable state, and the vertical displacement and stress of the rock mass show a significant nonlinear and rapid growth trend. When the reduction factor is in the range of 2.25 to 3.5, the internal fractures of the rock mass further expand, the scope of the loosened zone continues to increase, the bearing capacity of the rock mass reaches its limit, and large-scale collapse occurs. (3) FLAC3D numerical simulation reveals that the failure of the ancient cavern group first occurs in the fish-tail pillars, mainly in the form of punching shear and inward folding failure; followed by the vault and arch foot, which are mostly subject to sliding shear failure. The research results provide a theoretical basis for the protection of underground caverns and stone cultural relics.

Mechanical Characterization and Damage Prediction of Rock Masses in the Cuiguangyan Ancient Cave Group

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发表日期：

2026年1月21日

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Yiwen Liang,
Jianping Fang,
Yong Wen,
Xiaodong Zhang,
Yongbing Liu

摘要

The accurate selection of rock mass mechanical parameters is crucial for the support design of underground caverns and the evaluation of their overall stability. Longyou Grottoes, known as the "Ninth Wonder of the World," have suffered extensive damage in some caverns due to weathering, aqueous solution erosion, human activities, and other factors. After a critical review of the deficiencies in the Hoek–Brown strength criterion and its existing modifications, this study introduces correction coefficients (K_m) and (K_s) that consider both the degree of rock mass disturbance and the nonlinearity of the Hoek–Brown strength criterion. A more reasonable method for determining the empirical parameters m_b and s is proposed, and an improved formula for the Hoek–Brown strength criterion is thereby derived. Based on this improved empirical formula of the Hoek–Brown strength criterion, more reasonable rock mass mechanical parameters for the ancient cavern group are obtained. Additionally, a numerical model of the Cuiguangyan ancient cavern group is established using the "RHINO-GRIDDLE-FLAC3D" combined approach, and the strength reduction method is employed to predict and analyze the failure characteristics of the ancient cavern group. The research results are as follows: (1) The corrected K_m and K_s are characterized by the integrity coefficient K_v, which not only reflects the degree of rock mass disturbance but also conforms to the nonlinearity of the Hoek–Brown strength criterion, thus overcoming the limitations of previous improved formulas. (2) Using the strength reduction method, it is found that the failure process of the ancient cavern group can be roughly divided into three stages: When the reduction factor ranges from 1.0 to 1.5, the vertical displacement and stress of the rock mass exhibit an approximately linear relationship with the reduction factor. When the reduction factor is between 1.75 and 2.25, a large number of new fractures or cracks appear inside the rock mass; at this stage, the plastic zone gradually transforms into a loosened zone, the entire cavern is in a critically unstable state, and the vertical displacement and stress of the rock mass show a significant nonlinear and rapid growth trend. When the reduction factor is in the range of 2.25 to 3.5, the internal fractures of the rock mass further expand, the scope of the loosened zone continues to increase, the bearing capacity of the rock mass reaches its limit, and large-scale collapse occurs. (3) FLAC3D numerical simulation reveals that the failure of the ancient cavern group first occurs in the fish-tail pillars, mainly in the form of punching shear and inward folding failure; followed by the vault and arch foot, which are mostly subject to sliding shear failure. The research results provide a theoretical basis for the protection of underground caverns and stone cultural relics.