Study On The Influnce Of The Initial Support's Deficiencies On Stability Of Tunnel

Boil-shotcrete support is the short title of shotcrete support and boil support. Moreover, shotcrete, boil and monitor measurement are considered as the three great supports, it is thus clear that boil-shotcrete support is quite important during the construction process of New Austrian Tunneling Method.Load-bearing circle is consist of shotcrete, boil and wall rock, which form initial support of New Austrian Tunneling Method. During tunnel constracting process, realizing the deformation of initial support and wall rock by monitor measurement on site. When tunnel's wall rock has tend to stabilization , the secondary lining can be begun. But, during the construction process of tunnel's initial support, there are a series of problems frequently, which lead to deficiencies of initial support's quality. For example, the thickness deficiencies of shotcrete , the length deficiencies of boil. Therefor, it is necessary to study the influence of initial support's deficiencies on stability of tunnel. The main work and results of this paper are as follow:â‘ Summarize the results researched by predecessors, classify and summarize the structural deficiencies of initial support. Two of the typical deficiencies are : the thickness deficiencies of shotcrete , the length deficiencies of boil.â‘¡Simulate and analyze the tunnel under actual design parameters by numerical simulation method. We can get that when the wall rock's grades become lower, the values of arch crown subsidence and horizontal convergence become larger.â‘¢Finite element analyze the typical deficiencies of initial support by numerical simulation method,study the the influence of initial support's typical deficiencies on safety and stability of tunnel. The results can be obtained : the decrease of shotcrete layer makes peripheral displacement increases ; Axial force of bolt increases distinctly where the shotcrete layer was lost; Axial force of arch crown bolt increases when bolt length decreases.â‘£Sorte out and analyze the results of monitor measurement on site, educe conclusions and put forward proposals of further study.