Study on Advanced Support and Anchor Directional Prerein for Cement of Layered Soft Rock Tunnel

To explore the directional pre-reinforcement method adapted to the bedding characteristics of large deformation tunnel, relying on Jiumian Highway large deformation tunnels, the parameters of surrounding rock were determined by rock test. The effect of directional reinforcement method was verified by adjusting the angle of bolt and advanced support and the spacing of small pipe under different large deformation grades and horizontal and longitudinal bedding angles in numerical simulation. Tunnel deformation in three large deformation levels field test section is significantly improved, which verifies the applicability of the method. The results show that: (1) The compressive stress in support structure is caused by the surrounding rock deformation and extrusion, bolt and the advanced support optimization affect the bolt and small pipe stress, and then change the support tension. The effect of bolt and small pipe optimization increases with the increase of large deformation grade. (2) Under plane bedding, the anchor rod angle directional reinforcement has a significant effect. Advanced directional reinforcement can be considered for strong large deformation when double-layered small pipes are used. Different bedding angles have different sensitivities to bolt and advance support optimization. (3) When the longitudinal stratification is inclined downward, insertion angle was optimized by increasing the angle between small catheter and longitudinal bedding; When the longitudinal bedding is inclined upwards, the turning point of surrounding rock deformation rate with the decrease of small pipe spacing is found to determine the optimal spacing. The optimal spacing decreases with the increase of large deformation grade and the longitudinal bedding angle.