Analytical model for tunnel face stability considering zonal weakening effect of rock mass parameters

Blasting excavation causes significant engineering disturbance and stress redistribution in the surrounding rock, leading to unavoidable strength loss, which negatively impacts the rock tunnel face stability. This study accounts for the weakening effects of rock strength parameters and their distance relationship with the blast location, introducing a weakening factor to quantify the degree of rock parameter degradation at different locations caused by blasting. By integrating the weakening factor with the Hoek–Brown criterion and employing an advanced three-dimensional spatial discretization technique alongside the limit analysis method, a tunnel face stability analysis model encompassing varying degrees of rock mass degradation is constructed. Then, incorporating the effects of continuous blasting, a stability analysis model of the tunnel face under multiple excavation steps is further developed. The main factors influencing the tunnel face stability, such as rock mass quality, high/weak disturbance degree, partition ranges, excavation steps, and tunnel depth, are analyzed, and the collapse areas simulated are visually presented. The results provide a reliable basis for the stability assessment and support control of the rock tunnel face.