米拉山隧道软弱围岩大变形施工防控技术

Prevention and Control Technology for Large Deformation While Constructing Mira Mountain Tunnel with Weak Rock

米拉山特长隧道位于西藏高海拔高寒地区,空气稀薄、气压低、自然条件和地质条件恶劣,且面临着围岩变形失稳、突泥、涌水、施工通风等诸多工程技术难题,是国道318线林拉公路工程工布江达至墨竹工卡段改造的重点控制性工程;米拉山隧道在软岩大变形段施工中出现了坍塌、大变形、初支开裂、掌子面失稳等多种病害问题;结合工程实践,全面总结了针对这些病害的处理措施,在此基础上,从隧址区周边踏勘、加强超前地质预报、监控量测、增大预留变形量、初期支护设计、预控制掌子面变形坍塌、预控制中下台阶落底开挖变形坍塌、软弱围岩内支撑施工方法和地表加固等方面,系统提出了软弱围岩施工大变形预防控制措施,为类似工程的施工提供了经验。

The Mira mountain long tunnel is located at high altitude and cold area in Tibet.The air is thin,the pressure is low,the natural conditions and geological conditions are bad,and it is faced with many engineering technical problems such as deformation and instability of surrounding rock,mud inrush,water gushing and construction ventilation.It is the key control project of the transformation of the 318Linzhi-Lasa highway project from Gongbo'gyamda to Maizhokunggar.In the construction of the Mira mountain tunnel,many diseases such as collapse,large deformation,initial branch cracking,and the instability of the tunnel face appeared in the large deformation section of the weak surrounding rock.Combined with the engineering practice,the measures to deal with these diseases were summarized.On this basis,the prevention and control measures for large deformation of soft rock were pat forward through reconnaissance of the tunnel site,strengthening the geological forecast,monitoring surveying,increasing the reservation deformation,design of primary support,advance control of deformation of tunnel face,advance control of deformation and collapse of middle and under bench excavation,internal bracing construction method of soft rock,surface reinforcement and other methods,which could provide experience for the construction of similar projects.