Mud inrush disaster is a typical geological disaster during the construction of mountain tunnels, which may bring immense economic losses and is very harmful to the local environment. Permeation grouting is an important treatment method for mud inrush disaster, which has been wildly used in China. In this paper, a theoretical model of permeation diffusion of Bingham fluid considering gravity is presented. A set of visual permeation grouting experiment device was designed. The test results verify the new permeation diffusion model showing that the slurry is spherical diffusion, while the strip-shaped diffusion appears under the spherical diffusion. With the increase of grouting quantity, the spherical diffusion radius increases gradually. Meanwhile, both the number and radius of the stripshaped diffusion increases gradually. The regression analysis of grouting quantity of 30 typical test data shows that the degree of influence of the grouting quantity from big to small is: grouting pressure, permeability coefficient, and water-cement ratio. The statistics of the total grouting quantity and the grouting quantity of spherical diffusion indicate that the grouting quantity of strip-shaped diffusion accounted for about 50%, which shows the importance of strip-shaped diffusion in surrounding rock reinforcement. This new diffusion model has certain guiding significance for practice.

The Yonglian tunnel in China has experienced 15 instances of severe water and mud inrush disasters, resulting in a total volume of 53,000 m³ of gushing water and mud. These disasters have caused irreversible environmental damage, including hilltop collapse and soil erosion. To achieve early warning and early management of such disasters, the paper introduced the Fuzzy Comprehensive Evaluation Method into the Analytic Hierarchy Process to establish a new quantitative evaluation index system for the causal factors. As the evaluation method involves expert participation in scoring, it inherently presents certain subjective elements. To further substantiate the validity of our approach, we conducted a series of model tests. Then, the accuracy of the quantitative evaluation indexes was verified through these model tests, indicating that the quantitative evaluation system has important guiding significance for safe tunnel construction, allowing for early warning and management of potential disasters.