浅埋大断面隧道过破碎带开挖支护方案对比研究——以青岛地铁6号线创智谷站为例

Comparative Analysis of Excavation and Support Schemes for Shallow-Buried Large Cross-Section Tunnels Crossing Fracture Zones:a Case Study of Chuangzhigu Station on Qingdao Metro Line 6

为避免过破碎带时发生拱部大变形、地面坍塌等问题,设计以预应力锚杆-分部台阶法为核心的过破碎带开挖支护体系,通过构建数值模型与中空注浆锚杆-CD法进行对比,并开展现场应用进行实践验证。研究结果表明:1)预应力锚杆-分部台阶法施工方案对围岩变形的控制效果优异,从模拟结果来看,围岩在拱顶沉降量、水平方向位移、开挖扰动范围均具有显著优势,在拱部贯通后,分部台阶法与CD法最终变形量分别稳定在6.8 mm和11.5 mm。2)从主动支护现场监测结果来看,拱顶的沉降量主要集中在(1)导洞开挖期间,演化过程可划分为加速、发展与稳定3个阶段。3)格栅钢架应力以受压为主,拱顶应力值大于拱腰、拱脚,最大达90 MPa;锚杆轴力随隧道的开挖经历了预应力损失、波动及保持稳定3个演化阶段,在稳定后变化量不超过0.1 kN/d。

To avoid arch large deformation and ground collapse when tunneling through fracture zones,an excavation support system of the prestressed anchor bolt and bench method is designed for tunnels crossing fracture zones.The system is numerically modeled and compared with the hollow grouting anchor bolt and the central diaphragm(CD)method,and field tests are performed.The results reveal the following:(1) The prestressed anchor bolt and bench method have an excellent control effect on the surrounding rock deformation;simulation results show that the controlling effect of crown settlement,horizontal displacement,and excavation disturbance range of the surrounding rock in the recommended methods is superior.After arch penetration,the final surrounding rock deformations using the bench method and the CD method are stable at 6.8 mm and 11.5 mm,respectively.(2) The active support site monitoring results indicate that the settlement of the crown is mainly concentrated during the excavation of guide hole No.1,and the evolution process can be divided into acceleration,development,and stability stages.(3) The grating steel frame′s stress is primarily compressive,with the crown stress exceeding 90 MPa;the axial force of the anchor bolt evolves through three stages with tunnel excavation:prestress loss,fluctuation,and stability,with the change not exceeding 0.1kN/d after stabilization.