Research On Deformation Characteristics And Reinforcement Measures Of The Weak Surrounding Rock In Banzhulin Tunnel

Lots of rail way tunnels and highway tunnels had built in China in recent years. The surrounding rock has the characteristics of poor stability and complicated deformation etc, once a tunnel is constructed in weak rock. The geologic hazards as large deformation and rheology of weak rock is always being a weakness and a problem of entire tunnel. So one of the urgent problem now is the research on deformation characteristics and reinforcement measures of the weak surrounding rock.Author studied on the weak surrounding rock of Banzhulin tunnel, analysis and sum up its deformation characteristics with the tunnel's monitoring and measuring data in construction process. And researched on the different excavation methods and mechanical effect of weak surrounding rock and lining of Banzhulin tunnel by elasto-plastic finite element method in numerical simulation. Furthermore, author demonstrated and sum up reinforcement methods and measures of the weak surrounding rock. The primary fruit is listed as follows.(1)Three-dimensional and time effect of weak rock deformation of Banzhulin tunnel's typical cross-sections' were emphases within analysis of the monitoring and measuring data. Results show the vertical convergence deformation of tunnel's arch crown are bigger than the horizontal of tunnel's side wall. As the part of Banzhulin tunnel located in the weak rock, it had a large deformation, uneven pressure at arch crown, sheared and extruded behavior and lining damaged. The surrounding rock of IV and V distinctions were going to be stability about one month after excavation, as well as the weak surrounding rock which have large deformation taking months. The surrounding rock's deformation-time curve have parabola-style and ladder-style, but its deformation-three dimensional curve have parabola-style and "厂"style. The deformation of the surrounding rock in Banzhulin tunnel has strong three-dimensional effect.(2) Results of full face method, step excavation method and single-side heading method numerical simulation show the heading and bench method is scientific and feat for the port of Banzhulin tunnel. According the results of three dimensional numerical simulation, the surrounding rock with marked convergence distribute in half diameter area away from excavation outline, and this is key area in construction process. Invert should be constructed quickly to reinforce intrados as the excavation of the heading and bench method cause stress concentration at most time. Most bolt have low axes force, all shotcreting bear compression stress and the top of side wall produce maximal compression stress and shotcreting will get crack along the lengthwise direction in the construction process. For controlling the stress condition of the top of side wall, monitoring and reshotcreting will be essential. Support units are safe and have a good state.(3)To reinforce and protect the weak surrounding rock, compared with different reinforcement methods, summarized the reinforcement measures of the weak surrounding rock of Banzhulin tunnel which have large deformation, shotcrete and rock bolt inject should be basic, no matter for the weak rock or special geologic condition stratum.