高地应力大变形隧道支护系统的试验研究

In-situ study of reinforcement systems for tunnels under high geo-stress and large deformation

乌鞘岭隧道穿越由多条断层组成的挤压构造带,存在较高的地应力,而且,岭脊段穿越的板岩夹千枚岩地层,围岩破碎,强度极低,施工初期出现了罕见的初期支护大变形,喷射混凝土严重开裂、破损,型钢钢架扭曲变形,部分出现折断,严重影响了施工安全与工程进度。为解决高地应力、大变形隧道工程的稳定控制技术难题,在工程现场设置了4种不同的支护参数工程试验段,实施了隧道表面位移与结构内力监测,以围岩与支护结构变形为主要评价指标进行了对比分析,研究结果表明:1)隧道拱脚与拱腰处局部大变形和偏压作用是隧道初期支护结构的扭曲与破坏的主要原因;2)柔性预应力锚索可取代临时横向支撑,初期支护H175钢拱架优于常用的I20钢拱架;3)以H175钢拱架+柔性预应力锚索+钢纤维喷射混凝土为结构组成的初期支护系统,能够较好地控制乌鞘岭隧道高地应力软弱围岩大变形。

The Wushaoling tunnel passes through a squeezing tectonic region involving several faults.Due to the high geo-stresses,the phyllite-containing slate at the mountain ridge is fractured and extremely low in strength.At the beginning of the construction,the primary reinforcement system underwent large deformation,resulting in serious distortion,cracks and damages to the shotcrete and the shape-steel arches.Four trial sections with different reinforcement parameters were installed at the site,and evaluation based on the construction monitoring information is made about the deformation of the surrounding rock mass and the reinforcement structures.The in-site study indicated that failure of the primary reinforcement structure resulted from the large deformation of the tunnel spring and the wall as well as the side earth pressure;the flexible prestressed anchor could replace the temporary strut;the H175-shape steel arch was a better primary support structure than the I20-shape steel arch;the primary reinforcement system composed of the H175-shape steel support,the flexible prestressed anchor and the steel fiber reinforced concrete was effective for control of the large deformation of the tunnel.