山岭隧道软弱围岩工程地质特性及施工对策

Engineering Geological Properties of Soft Surrounding Rocks of Mountain-crossing Tunnels and Construction Countermeasures

如何在软弱围岩地质条件下安全快速地修建长大隧道是当前隧道工程界面临的重要课题之一,尤其是当隧道穿越高地应力软弱围岩时,常常形成大变形等地质灾害,严重影响施工安全和进度。通过对软弱围岩工程地质特性、软岩隧道变形机制及变形控制基本理念进行分析,并结合相关工程实例提出软岩隧道支护结构安全稳定性评判标准及施工应采取的相应对策。认为:1)软弱围岩隧道由于支护参数、施工方法选择不当,支护结构强度和刚度不足以抵抗较高的围岩压力时,往往会出现结构大变形和破坏;2)软岩地段初期支护承受施工期间全部荷载,二次衬砌需承受后期围岩流变产生的荷载,软岩隧道衬砌应通过增设钢筋、加大厚度等方式增加结构强度;3)超前支护与加固技术可提高围岩的自承能力并减小作用在支护结构上的荷载,且应当成为当前软弱围岩隧道施工技术研究的发展方向;4)在高地应力山岭隧道方面,应进一步开展施工阶段地应力测试,以利于针对性地选择施工方法和支护参数。

Safe and rapid construction of tunnels in soft surrounding rocks becomes more and more important.Especially when tunneling through soft surrounding rocks with high ground stress,serious deformation may occur,which may jeopardize the construction safety and the construction progress.In this paper,the engineering geological properties of soft surrounding rocks,the deformation mechanisms of tunnels in soft surrounding rocks and the basic deformation control concepts are analyzed,and the criteria for the safety and stability of the support structures of tunnels in soft surrounding rocks and the construction countermeasures are proposed.Conclusions drawn are as follows：1 ）Due to the improper support parameters and construction methods adopted,the strength and rigidity of the support structure cannot resist the huge surrounding rock pressure and therefore serious deformation and failure may occur;2 ）In soft surrounding rock section,the primary support takes all the loads during construction,the secondary lining needs to take the loads caused by the deformation of the surrounding rocks in the later stage,and the lining of the tunnel in soft surrounding rocks should be strengthened by means of adding steel bars and increasing the lining thickness.3）Advance support and reinforcement can improve the self-support capacity of the surrounding rocks and can reduce the load acting on the support structure, therefore the advance support and reinforcement should be the focus of studies on construction technologies of tunnels in soft surrounding rocks;4）For mountain-crossing tunnels in high ground stress area,ground stress measurement should be further implemented so as to select proper construction methods and support parameters.