某水工隧洞洞口段围岩稳定性监测实践

Monitoring Practice of the Stability of Surrounding Rock at the Portal Section of Some Hydraulic Tunnel

以某水工隧道洞口段工程为依托,在分析工程特点和周边环境的基础上,确定以地表沉降、净空收敛、拱顶下沉和锚杆轴力为监控量测项目的监测方案,并结合监测数据对隧道洞口段的围岩稳定性进行研究分析。结果表明:净空收敛、拱顶下沉的变形趋势接近一致,在下台阶及底基层的开挖过程中整体变化量为70%~90%;洞身开挖对地表沉降影响范围是洞径的5倍。监控量测方案能准确反映隧道洞口段施工过程中的围岩稳定状态,可以满足施工安全的需要,对类似围岩稳定监控具有一定的参考价值。

Based on the analysis of the engineering characteristics&surrounding environment of a certain hydraulic tunnel entrance section,a monitoring plan is determined to monitor&measure surface settlement,clearance convergence,arch crown settlement,and anchor rod axial force.The stability of the surrounding rock in the tunnel entrance section is studied&analyzed using monitoring data.The results show that the deformation trend of clearance convergence&arch crown settlement is close to the same,with an overall variation of 70%to 90%during the excavation process of the lower steps&subbase;the impact range of tunnel excavation on surface settlement is 5 times that of the tunnel diameter.The monitoring&measurement plan can accurately reflect the stable state of surrounding rock during the construction process of the tunnel entrance section,and can meet the needs of construction safety.It has certain reference value for similar surrounding rock stability monitoring.