A quantitative risk assessment method for tunnel water inrush disasters is developed to enhance safety risk prevention capabilities under the influence of water-bearing structures. Addressing the water inrush risks induced by the coupling effects of water-bearing structure spatial positioning and surrounding rock disturbance, an integrated evaluation methodology combining geological detection and mechanical analysis is proposed. The methodology comprises three core components: First, the transient electromagnetic method is employed for advanced water detection to accurately identify the three-dimensional spatial distribution of water-bearing structures. Second, graphical analysis is applied to partition the surrounding rock disturbance into failure zone D_f, stress-disturbed elastic zone D_e, and natural stress zone, establishing a spatial superposition risk assessment model between water-bearing structures and disturbance zones. Finally, for medium or high-risk scenarios, a danger coefficient K_c calculation formula constrained by force equilibrium is derived to dynamically adjust risk levels. Engineering validation demonstrates: When a water-bearing structure in a tunnel case was 9.00 m from the tunnel wall, combined with disturbance boundary values of D_f = 2.40 m and D_e = 12.65 m, the initial risk assessment identified medium risk. After recalculating K_c = 0.87, which is less than 1.00, the risk level was upgraded to high, consistent with subsequent actual water inrush incidents. Two key achievements are summarized as follows: a dual-level risk assessment framework of “preliminary determination-quantitative recheck” is established, achieving the transition from qualitative to quantitative risk grading, and the defined boundary values of the disturbance zone can provide a scientific basis for the minimum safe distance in advanced geological detection. The research outcomes form a complete technical system covering the entire process of “detection-analysis-evaluation-prevention” for tunnel water inrush risks, substantially improving assessment accuracy and offering innovative solutions for safe tunnel construction in complex geological conditions.