Calculation Method Of Surrounding Rock Pressure And Stress Analysis Of Excavation For Shallow Highway Tunnel

China is a mountainous and hilly country, with China's economic development, the transport of mountainous areas develops quickly, more and more mountain road tunnels have been constructed. In recent years there have been several large natural disasters in China, such as WenChuan earthquake, YuShu earthquake, highway tunnels are also damaged seriously. The surrounding rock of shallow tunnels usually has lower strength, it's difficult to form a natural arch in the excavation, so shallow tunnels are unstable. The calculation of shallow tunnels are different from the deep tunnels, the main theories are the soil column method, the Tai Shaji theory, and the method in the design of road tunnel. It's easy to produce the sliding surface, and has plastic deformation in the process of shallow tunnel's excavation, so the stress analysis is particularly important.The main work of this paper is as following:1. It establishs the finite difference calculation model using the FLAC3D software, According to the geological condition of Zhaojiagou tunnel. It includes four models of different depth, it uses static analysis, and has the comparative analysis for the plastic zone of the model, gets the results that the vault and arch are determined to the most susceptible to tension and shear failure.2. It has the analysis and comparison of each model's vertical stress and shear stress in the excavation. The end of the main arch and vault are tension failure, the lumbar arch is compressive failure. The hence and the foot of arch are likely occur shear failure. Greater depth, the greater the stress.3. It has the analysis and comparison of each model's vertical displacement in the excavation, it gets the crown settlement ,the dome displacement increased, the greater the depth, the greater the displacement. It's monitors the stress and the vertical displacement of several feature point. The stress of lining and the support structure anchor were summarized in the excavation. Because of the modeling constraints of FLAC3D, this paper established a model of different tunnel widths.In summary, by the analysis of the force and deformation to different models in the process of excavation, there is a deeper understanding about the failure modes and the effection to the stress and deformation in different depth. It provide a reference to the design and construction of highway tunnels.