Influence of Underground Excavation Expansion on Surrounding Rock Characteristics at Intersection of Ventilation Shaft and Tunnel: A Case Study

Existing railways can no longer meet transportation requirements, and it is an urgent need to expand old tunnels. However, the existence of ventilations shaft makes expansions face greater risks. This study analyzed tangential stress change trend during expansion process through field monitoring, numerical simulation was used analyze changes in displacement under different depths width–span ratios. The results show that as one approaches tunnel face, arch foot side wall J-2 J-3 sections gradually increased, J-1 section decreased. distance expansion’s influence on about 0.91 1.45 times span. largest value vertical had a linear relationship with depth, horizontal quadratic depth. Changes ratio only impact ventilation section. These provide reference for similar situ projects.