浅埋连拱隧道施工动态响应特征研究

以实际工程为依托,针对浅埋连拱隧道暗挖施工稳定性问题,研究了隧道开挖过程中围岩、支护结构、中隔墙等结构的应力分布情况以及地表沉降等指标的动态响应特征。结果表明,中导洞开挖过程中,上台阶开挖对围岩应力影响较明显; 隧道施工完成后中隔墙上最大应力达7.03 MPa,侧洞拱腰及拱顶部位存在应力集中,大小为0.7~1.55 MPa; 侧洞靠近中导洞的上台阶初支结构拉应力达1.67 MPa,侧洞远离中导洞的上台阶初支结构压应力达4.48 MPa; 侧洞靠近中导洞侧台阶开挖时中隔墙应力增幅明显,掌子面远离监测面超20 m后施工对中隔墙无影响; 地表沉降最大部位位于隧道轴线处,沉降最大值为7.20 mm,沉降区域半径约25 m。

Dynamic Response Characteristics of Ground in Construction of Shallow-Buried Double-Arch Tunnel

In view of the stability problem caused by  construction of shallow-buried double-arch tunnel in an actual project, the stress distribution of surrounding rock, supporting structure, partition wall and the dynamic response characteristics such as ground subsidence during  underground excavation were studied. During the excavation of the middle pilot tunnel, the excavation of upper step brought obvious influence to the stress of surrounding rock. After the completion of tunnel construction, the maximum stress on the partition wall reached 7.03 MPa, and there was stress concentration at the waist and vault of the side tunnel, ranging from 0.7 MPa to 1.55 MPa. The tensile stress of the initial support structure of the upper step near the middle pilot tunnel was 1.67 MPa, and the compressive stress of the initial support structure of the upper step far away from the middle pilot tunnel was 4.48 MPa. When the side tunnel was close to the side step of the middle pilot tunnel, the stress of the partition wall increased obviously, but the construction had no influence on the partition wall if the working face was more than 20 m away from the monitoring face. The position located at the axis of the tunnel appeared to have maximum ground subsidence, up to 7.20 mm, with the radius of subsidence area of around 25 m.