Tunnel projects within Karst landscapes are frequently plagued by the unpredictable occurrence of water inrush disasters. Detecting and predicting the emergence of fissure-type water inrushes pose substantial difficulties and convey a high disaster risk. In order to shed light on the mechanisms behind fissure-type Karst water inrushes and delineate potential early warning indicators, grounded in the "fluid-solid-damage" coupling model, both the causative mechanisms and threshold conditions that precipitate fissure-type Karst water inrushes were investigated. By rigorously deriving formulas and conducting comprehensive multi-field coupled numerical analyses, key conclusions are reached as follow. A robust "fluid-solid-damage" coupled mathematical model has been effectively formulated. This model provides a detailed illustration of the disaster mechanisms associated with fissure-type Karst water inrushes, and its feasibility and rationality have been empirically confirmed. The displacement evolution of tunnel vault surrounding rock under different pressure conditions is analyzed which demonstrates a strong correlation between fissure-type Karst water inrushes and increased water pressure within the water-rich solution cavities. Upon assessing the characteristics of the surrounding rock under critical water inrush conditions, a triphasic evolution model characterized by "slow growth-rapid growth-displacement runaway" phases specifically for fissure-type Karst water inrush events has been postulated.