新乌鞘岭隧道岭脊段高地应力软岩大变形控制技术

Solution of Large Deformation Control for Soft Rock under High Geostress in Ridge Section of New Wushaoling Tunnel

针对新乌鞘岭隧道岭脊段高地应力软岩变形问题,采用加强初支、铣挖法施工在软岩大变形方面取得了良好的效果。通过调整仰拱曲率、加大变形预留量、加强初期支护、超前预加固等设计支护措施,结合铣挖法开挖可有效减少对周边围岩的扰动,有效控制软岩塑性区的发展。研究表明:相比钻爆法,采用铣挖法开挖易于控制超欠挖,并大幅度降低对围岩的扰动。轮廓平均线性超挖由37 cm缩减至17 cm,超挖率由121%缩减至61%,喷射混凝土与岩面密贴性好,有利于提升围岩自承能力和初期支护的承载能力,可有效改善变形控制效果,提高软岩施工的进度及安全性,可作为高地应力软岩大变形控制的有效方法。

In order to address the challenges posed by high geostress-induced deformation in the ridge section of the New Wushaoling Tunnel,a solution of reinforcing primary support and milling excavation measures has been implemented,resulting in the successful control of significant soft rock deformation.In addition to design and primary support measures,such as adjusted invert curvature,increased deformation allowance,reinforced primary support,and advanced pre-reinforcement,a milling excavation method was also employed to effectively minimize disturbance to the surrounding rock and control the development of the plastic zone dominated by soft rock.The study shows that the milling excavation method offers advantages over the traditional drilling-and-blasting method,facilitating easier control of over-excavation and under-excavation while significantly reducing disturbance to the surrounding rock.Specifically,the average linear over-excavation in the contour decreased from 37 cm to 17 cm,and the overbreak rate decreased from 121%to 61%.Moreover,the proposed method achieved good adhesion between the shotcrete and rock surface,enhancing the self-supporting capacity of the surrounding rock and the supporting capacity of the primary support system.Overall,this control solution demonstrates improved deformation control,progress management,and construction safety in soft rock environments with high geostress conditions,thus making it an effective approach for managing large deformations in such geological settings.