Study On Control Technology Of Schistose Basalt Tunnel Under Large Deformation

In this paper,based on the background of the schistose basalt section of Zhongyi Tunnel,the field test and numerical simulation technology are used to explore the influence characteristics,deformation distribution law and deformation control measures of schistose basalt section.The main conclusions are as follows:(1)The ground stress,support strength and surrounding rock grade of Zhongyi Tunnel are important factors that affect the deformation of surrounding rock.When the ground stress increases,the deformation law of tunnel surrounding rock is that the deformation increases with similar amplitude.When the strength of tunnel support and surrounding rock is enhanced,the deformation law of tunnel surrounding rock is that the deformation amount decreases to a certain extent.The influence of excavation deformation on the surrounding rock range beyond 7 times of tunnel diameter is weak.(2)The deformation characteristics of the schistose basalt tunnel are characterized by fast deformation rate,large accumulated deformation and long creep time.Its disaster prominent part is the side wall of lining.The deformation mechanism is mainly extrusion deformation under the action of extremely high surrounding rock pressure,which is the result of interaction between swell and shear slip of surrounding rock.(3)Aiming at the large deformation of schistose basalt in the main section of Zhongyi Tunnel,three large deformation control schemes are designed,and numerical simulation and field test are carried out for each scheme.Finally,the scheme of large deformation type II & surrounding rock reinforcement is selected.Through the comprehensive measures of increasing the section curvature,accelerating the closed-loop time and increasing the support and surrounding rock strength,the large deformation of the surrounding rock is successfully controlled,and the probability of replacing the arch in the section with large deformation is reduced to 0%.The results show that the main controlling factors of the large deformation of the tunnel are the curvature of the section,the time of the closed-loop and the strength of the support.(4)Aiming at the large deformation of broken schistosity basalt in the horizontal guide section of Zhongyi Tunnel,four control schemes are designed,and numerical simulation and field test are carried out for each scheme.Finally,the scheme of single-layer initial support & h175 reinforced steel arch & additional i18 reinforced arch & excavation of invert and lower bench respectively is selected,which successfully controlled the large deformation of surrounding rock and reduced the arch replacement rate to 0%.The results show that the main controlling factors of the large deformation of the tunnel are the support strength and the strength of the surrounding rock of the side wall.