杉阳隧道软岩大变形控制方法及结构力学特性研究

Study on Large Deformation Control Method and Structural Mechanical Characteristics of Shanyang Tunnel in Soft Rocks

为有效控制大瑞铁路杉阳隧道薄层状破碎页岩段软岩大变形,提出帷幕注浆、超前中管棚和超前探水泄压孔的围岩预加固措施配合三台阶机械法开挖的施工方法。通过增加边墙开挖曲率将马蹄形开挖断面优化至蛋形断面,预留变形量由10 cm增加至50 cm,初期支护结构由间距1 m的I25单层钢拱架调整为间距0.6 m的双层HW175钢拱架等一系列措施解决了现场钢拱架扭曲、断面侵限等难题。通过现场支护结构受力监测,双层初期支护的部分钢拱架受力超过其屈服强度,原因主要为支护结构受力过大,未充分释放围岩荷载。建议释放一部分围岩压力后再施作第二层初期支护。

In order to effectively control the large deformation of soft rock in the thin-bedded broken shale section in the Shanyang Tunnel on Dali-Ruili Railway,a construction method has been proposed that is comprised of surrounding rock pre-reinforcement by curtain grouting,advance middle pipe umbrella and advance water exploring and pressure relief holes and the three-bench mechanical excavation.The side wall excavation curvature is increased to change the U-shaped excavation section to egg-shaped excavation section,the deformation allowance increases from 10 cm to 50 cm,and the initial support structure changes from the I25 single-layer steel rib with 1 m spacing to the double-layer HW175 steel rib with 0.6 m spacing.All these measures have solved the challenging problems such as steel rib distortion and cross section intrusion.According to force monitoring on the support structure on site,the forces on some of the steel ribs of double-layer initial support exceed their yield strength,mainly because the support structure sustains excessive force while the surrounding rock load is not adequately released.It is recommended to release a part of the surrounding rock pressure before construction of the second layer of initial support.