针对大断面机场下穿隧道施工中爆破法扰动围岩的技术难题，以渝昆高铁长水机场隧道为依托，提出基于悬臂掘进机法的低扰动施工路径规划与围岩损伤演化分析方法。基于FLAC3D软件构建三维数值模型，采用分块多步开挖法模拟悬臂掘进机渐进开挖过程，通过渐进释放围岩荷载，精确表征机械开挖的低扰动特性。结合现场松动圈测试与孔内光学摄像，构建数值模拟与工程实测的交叉验证机制，重点分析悬臂掘进机施工路径及Ⅲ—Ⅴ级围岩条件下位移场、应力场及塑性区的时变特性。研究表明： 1)分块多步开挖法可有效模拟悬臂掘进机渐进式开挖特性，数值模拟结果与现场测试数据吻合度高，证实了该方法的科学性及适应性。2）相比于常规掘进路径，分块掘进路径可降低Ⅴ级围岩的拱顶沉降21.7%，有效控制围岩变形。3）围岩损伤特征呈现显著等级相关性，Ⅲ、Ⅳ级围岩损伤集中于隧道轮廓附近，塑性区以拉伸破坏为主； 而Ⅴ级围岩损伤范围扩大，剪切破坏占比显著增加。
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.
