Abstract: Blasting excavation of large cross-section tunnels beneath airports causes significant disturbance to surrounding rock masses. This study focuses on the Changshui Airport tunnel, part of the Chongqing-Kunming high-speed railway, and proposes a low-disturbance path planning and damage evolution method based on cantilever roadheader excavation. A three-dimensional numerical model is developed using FLAC3D to simulate progressive excavation via a segmented multistep method, which incrementally releases rock stress and captures the low-disturbance characteristics of mechanical excavation. Field validation is conducted using loosened zone tests and borehole optical imaging, establishing a cross-validation system between simulations and measurements. Time-dependent behaviors of displacement, stress, and plastic zones are analyzed for Grade Ⅲ to Ⅴ surrounding rock during excavation. The main findings are: (1) The segmented multistep method effectively simulates roadheader excavation, and numerical results align well with field observations, validating the approach′s scientific basis and adaptability. (2) Compared with conventional excavation, the segmented method reduces crown settlement by 21.7% in Grade Ⅴ rock, indicating superior deformation control. (3) Damage exhibits clear grade dependence, in Grades Ⅲ and Ⅳ, tensile-dominated plastic zones concentrate near tunnel boundaries; in Grade Ⅴ, damage is more extensive and governed by shear failure.

Key words: cantilever roadheader, tunnel crosses beneath airport, surrounding rock damage, loose zone test, numerical simulation, path planning