高地应力千枚岩隧道支护体系试验研究

成兰铁路茂县隧道穿越龙门山活动断裂带,地层以千枚岩为主,围岩破碎、软弱、强度低,且存在高地应力。在茂县隧道1号斜井施工过程中,遇到了围岩大变形、喷射混凝土开裂、钢拱架扭曲等现象。为了解决这一技术难题,在施工现场将斜井按正洞施作,设置4种不同的支护体系试验段,并对围岩变形、围岩与初支接触压力、钢拱架应力进行监测分析,得出以下结论:I20工字钢刚度低,不能有效地抵抗围岩前期变形,使围岩的变形进入塑性流动阶段;H175型钢刚度大,与3 m长短锚杆相结合能主动控制围岩的变形,能有效地控制围岩前期变形,8 m长的锚杆能被动控制围岩变形,能有效地抑制围岩塑性区的扩大;以H175钢拱架+3 m锚杆+8 m锚杆+喷射混凝土+超前注浆小导管为主的初期支护体系对茂县隧道高地应力千枚岩大变形的控制有较好的效果,可为后期茂县隧道正洞的施作提供指导。

Experimental Research on Support System of High Geostress Phyllite Tunnel

The Maoxian Tunnel of Chenglan Railway passes through the Longmenshan active fault zone. The stratum is mainly phyllite which is fractured, weak, low in strength and of high in-situ stress. During the construction of No. 1 inclined shaft, large deformation of surrounding rock, cracking of shotcrete and distortion of steel arch frame were encountered. In order to solve this technical problem, the inclined shaft is constructed according to the main tunnel in the construction site, and four different supporting system test sections are set up. The deformation of surrounding rock, contact pressure between surrounding rock and initial support, and stress of steel arch are monitored and analyzed. The following conclusions are drawn: I20 I-steel has low stiffness and can not resist the pre-deformation of surrounding rock, which makes the deformation of surrounding rock enter the plastic flow stage; H175 steel has high stiffness and can actively control the deformation of surrounding rock by combining with 3 m long and short bolts, which can effectively control the pre-deformation of surrounding rock, and 8 m long bolts can dynamically control the deformation of surrounding rock and effectively restrain the expansion of plastic zone; The initial support system mainly consisting of H175 steel arch frame and 3 m bolt and 8 m bolt and shotcrete and advance grouting duct has a good effect on controlling the large deformation of high geostress phyllite in Maoxian Tunnel and can provide guidance for the construction of the main tunnel in Maoxian.