Abstract: To ensure the safe passage of deep-buried tunnels through sections characterized by high-pressure water-rich karst caves, we investigated into the water inrush mechanism of the tunnel and determined the minimum safe thickness of waterproof rock mass. Based on the catastrophe theory, the Rubinett equation, and engineering experiences, we derived a calculation formula for the minimum safe thickness and established a water inrush criterion. We also scrutinized the influence of pertinent factors on the minimum safe thickness of the tunnel sidewall’s waterproof rock mass. Results indicate a positive correlation between the minimum safe thickness of the waterproof rock mass (H_min) and the mechanical parameters of surrounding rock, including elastic modulus (E) and internal friction angle (φ), while a negative correlation with the water pressure within the karst cave (q_w), the span of the rock beam (L), and the burial depth of tunnel (h). The influence of each factor on H_min ranks in an order of h, φ, E, L, and q_w from greatest to least, with h and φ exhibiting similar degrees of influence. Moreover, when E exceeds 3 GPa, the change in H_min tends to be stable, akin to the influence of L. Finite element simulations and empirical examples align with theoretical calculations, confirming the accuracy and applicability of the derived H_min theoretical calculation formula and the water inrush criterion. This synthesis of theoretical and empirical evidence offers guidance for relevant engineering endeavors.

Key words: deep-buried karst tunnel, water-rich karst cave, minimum safe thickness, catastrophe theory, criterion of water inrush