大断面蚀变软岩引水隧洞施工方案适宜性研究

Comparative Study on the Suitability of Construction Scheme of Large Section Altered Soft Rock Headrace Tunnel

以甘孜硬梁包水电站超长引水隧洞工程为依托,采用三维FLAC3D数值模拟,对不同施工方法进行了对比分析,验证开挖方法的合理性。研究发现蚀变岩隧洞上半洞开挖,以拱顶沉降为主,建议加强拱顶沉降监测。塑性区最大深度在拱肩位置,成为失稳的关键部位,需确保拱肩锚杆的施工质量。根据数值模拟计算结果显示,预留核心土法塑性区厚度6 m,最大变形为55 mm,台阶法开挖塑性区厚度15 m,最大变形为102 mm。因此确定预留核心土法为合理的施工方法。

Based on the ultra-long headrace tunnel of Yingliangbao Hydropower Project in Ganzi Prefecture,the three-dimensional FLAC3D numerical simulation is carried out to compare and analyze the different construction methods,and verify the rationality of the excavation method.It is found that the arch deformation is the main factor in the excavation of the upper half of the altered rock tunnel.It is suggested to strengthen monitoring of arch deformation.The maximum depth of the plastic zone is at the spandrel position,which becomes the key position of instability,therefor,the construction quality of spandrel bolt needs to be ensured.According to the numerical simulation results,the thickness of the plastic zone of the reserved core soil method is 6 m,and the maximum deformation is 55 mm.The thickness of the plastic zone of the step excavation method is 15m,and the maximum deformation is 102 mm.Therefore,the reserved core soil method is determined to be a reasonable construction method.