Research On The Optimized Design Of The Excavation-Mode And The Supporting-Scheme On The Highway Tunnel Of Lxw Project

Based on the finite element method theory, the process of the excavation and support of the highway tunnel of LXW project is simulated by the program system FINAL introduced from Austria. The mechanical parameters of the surrounding rockmass are established by Hoek-Brown criterion. In addition, the disturbing coefficient of surrounding rock which reflects the influence of excavation and explosion on rockmass is settled by observing the undulant surface of rockmass after excavation and explosion. Then, three typical sections of tunnel are calculated and the feasibility of the original design scheme is evaluated. Finally, based on the author's experience, the New Austrian Tunneling Method (NATM) is applied to optimizing the existing supporting scheme and the occasion of supporting system and evaluating the effect of pre-supporting and post-supporting.The deformation of surrounding rockmass and the area of plastic region when adopting the optimized support scheme have little difference with original resultswhen adopting the original support scheme, so the surrounding rocks are safe. When accepting the optimized support scheme, the thickness of lining concrete has been minished remarkably. The thickness of lining of K1+115 section has been shortened from 1.0 m to 0.6 m and the thickness of lining of K1+010 section has been shortened from 0.6 m to 0.4m. Furthermore the concrete lining and bolts play an important role in withstanding the external loads. From the above, we can draw a conclusion that the optimized support system is reasonable and reliable.