Tunnel is a construction built underground, underwater or in the mountain by laying railway or highway to let motor vehicles passing through. Based on the site selection, tunnel is divided into mountain tunnel, submerged tunnel and city tunnel. Because of the specificity of its location, exploration and digging must based on the surrounding terrain, geology and distribution of underwater. To ensure road traffic more smooth, we should reinforce and advance pre-support the tunnel when construction.
At present, many supporting methods have great effect in good geological conditions, while in soft and complex conditions, such as crushing, high ground stress in tunnels with great deformation, the challenge for these supporting method is quite big. So soil nail at home and abroad is moving to the effect of improving anchoring force, efficiency of support and expanding application range. It is believed that developing soil nail with plenty properties is an effect way to control high stress and big deformation, which is also the direction of soil nail’s development.
Before tunnel construction, analogous calculation and analysis should be carried out, such as geological conditions, choice of parameters, digital simulation, supporting effect, displacement control analysis, stability of surrounding rocks, etc.
The steps of installing soil nail are as follow: drill holes, insert soil nail, grout slurry and lock steel arch.
During the construction of railway tunnel, soil nail has reaction with surrounding rocks, which depended not only on terrain conditions, but also on soil nail’s support effect.
In weak conditions, soil nail has better reinforcement effect. It can change the mechanical property of surrounding rocks, enhance self-supporting capacity, reduce deformation of surrounding rocks and then keep tunnel’s stability.