超大跨公路隧道洞口浅埋偏压处治方案研究

A Study on Treatment Scheme of Shallow Buried Deviation at Tunnel Entrance of Super-large Highway Tunnel

超大跨公路隧道浅埋偏压洞口段围岩软弱破碎,进出洞施工时开挖扰动大,围岩应力及围岩变形具有突发性、变化快的特点,易造成隧道塌陷破坏,导致安全事故。为确保隧道洞口浅埋偏压段围岩的稳定性和安全性,结合边坡工程的处治经验,采用微型桩群桩和地表钢花管注浆支护体系加固洞口的滑塌体,提高围岩强度,减小地表的不均匀沉降,在出洞时施作护拱反压回填并设置偏压挡墙平衡偏压力。本文以圆墩隧道深圳龙岗端洞口为例提出上述支护体系,并对该支护体系进行了受力分析,通过数值模拟结合现场监测结果找到相关规律,证明该加固系统可有效改善隧道浅埋偏压情况,为后续大跨度隧道洞口加固提供一定的参考价值。

The surrounding rock of shallow buried biased section of super long-span highway tunnel is weak and broken.During the construction of tunnel entrance and exit,the excavation disturbance is large.The stress and deformation of surrounding rock are characterized by sudden and rapid change,which is easy to cause tunnel collapse and safety accidents.In order to ensure the stability and safety of shallow buried biased section of tunnel entrance,combined with the treatment experience of slope engineering,the sliding body of tunnel entrance was reinforced by the support system of micro pile group pile and surface steel flower pipe grouting,with improving the strength of surrounding rock and reducing the uneven settlement of the surface.When exiting the tunnel,the arch back pressure backfill was applied and the biased retaining wall was set to balance the biased pressure.Taking the entrance of Shenzhen Longgang end of Yuandun tunnel as an example,the above support system was adopted and the force analysis of the support system was carried out.Through numerical simulation combined with the field monitoring results,the relevant laws were found.It is proved that the reinforcement system can effectively improve the shallow buried bias pressure of the tunnel.