To address the problem of complex and unobservable internal crack propagation within surface rock fissures sealed by freezing in alpine regions, this paper derives calculation formulas for the gas pressure inside the crack (GPIF) after freezing, the plastic zone around the crack, the stress intensity factor (SIF) at the crack tip, the crack initiation angle, and the crack initiation stress under the assumption of small-scale yielding, based on complex variable function theory and elastoplastic fracture mechanics theory, while analyzing the influences of key parameters freezing temperature \(T_i\) , ratio of gas volume to crack volume (RGVC) sa, and crack geometry on crack initiation characteristics. The results indicate that a minimum ice penetration depth (lmin) exists within the crack, and only when the length of the internal ice body exceeds lmin does it significantly compress the remaining gas to cause a substantial pressure increase; the post-freezing GPIF increases markedly only when \(s_a < 0.5\) , where a smaller RGVC, lower temperature, and shorter crack length yield a larger SIF with significant effects; when \(s_a > 0.5\) , GPIF changes negligibly impact fracture behavior, GPIF can reach up to 6 MPa when \(s_a = 0.1\) . The plastic zone size at the crack tip decreases with increasing \(s_a\) and major axis length \(a\) but increases with decreasing \(T_i\) ; the crack initiation angle ( \(\theta _0\) ) rotates counterclockwise as \(s_a\) increases, \(T_i\) decreases, and \(a\) increases, with the most pronounced variation occurring with freezing temperature changes.
