大跨度扁坦隧道施工力学三维数值模拟及现场监测分析

3D Numerical Simulation and Field Monitoring of the Excavation of a Large-Size Flat Tunnel

以昆楚高速勤丰三车道隧道紧急停车带段为工程背景,针对其跨度大、形状扁坦的特点,在对比分析了三台阶法和临时中隔壁法优缺点的基础上,确定采用三台阶法施工。通过三维数值模型对隧道三台阶法施工过程中隧道变形、支护受力和围岩塑性区分布特征进行分析,结果表明三台阶法可以保证隧道施工安全。在隧道施工过程中对隧道变形及支护受力进行了监测,监测结果表明,围岩压力和钢拱架应力均较小,保证了施工安全。

The tunnel section in the emergency stopping zone in a three-lane Qingfeng Tunnel of Kumming-Chuxiong Expressway has large size and a flat oblong cross section. Both advantages and disadvantages of two different tunnel excavation sequences, Three-Bench Method and Temporary Central-Wall Method, were evaluated and the three-bench excavation method was selected for the tunnel excavation. The entire process of the constructionsequence was numerically simulated, and the selected construction sequence was feasible and safe. The analytical results, such as, deformation in the tunnel, stress in the supporting structures and the plastic zones in the rock mass, were compared with the construction monitoring results. The results indicated that the stress in both the rock mass and steel arch supporting structures were small and the construction sequence was safe.