Research on the Influencing mechanisms of ice-filled fissures on the failure processes of tunnel specimens

• Fracture characteristics of fissure ice filling states on rock mass are analyzed. • The strength of fissured rock mass is significantly improved by ice filling. • Ice weakens the compressive degree through the “stress redistribution-weakening” effect. • Higher energy input is required for the failure of ice-filled fissure specimens. In cold-region tunnel engineering construction, the degradation mechanism of tunnel surrounding rock caused by rock fracture ice remains unclear. Existing studies primarily focus on fissured rock masses at normal temperature, which lack an understanding of the damage evolution laws of ice-filled fissures under complex stress conditions. In view of this, fissured tunnel specimens at various angles (0° − 90°) are prepared by employing sand 3D printing technology. Uniaxial compression tests are performed, combined with PFC2D numerical simulation, to systematically analyze the effects of fissure filling states (ice-filled/non-filled) on rock mass strength, crack propagation, and energy evolution. The results reveal that the peak loads of ice-filled fissure specimens are significantly greater than those of non-filled specimens. The ice inhibits stress concentration at fissure tips, causing the tunnel structure to be damaged preferentially. Compared with non-filled fissure specimens, ice-filled specimens require higher external energy input during loading, and after entering the failure stage, the elastic strain energy shows a declining trend, whereas the dissipated energy experiences a sharp increase. For the first time, 3D printing tests combined with numerical simulations have confirmed that ice-filled can weaken the stress field around fissures, promoting the tunnel to become a region where cracks tend to form. In contrast, non-filled fissures dominate the rupture process due to tip stress concentration. This study provides experimental evidence and theoretical support for the stability analysis of tunnel surrounding rock in cold regions.