Analysis And Treatment Of Structure Stability For Opening Excavation Of High Slope Shallow Buried Tunnel

In construction of highway tunnels, especially at the portals of the tunnels, the high slopes may be encountered usually. Because there are reasons of the design and location, the portals of the tunnels may be at the shallow strata and with undergone unsymmetrical pressure during excavation. In these cases, the slope may be unstable. Therefore, it is need to judge accurately the stability of the slope and taking effective treatment measures promptly. As the geological conditions are complex, it is need to study good methods to evaluate the slope stability to the portal excavation for different conditions at present.In this thesis Miaowan No.l and No.2Tunnels of Yiba(Yichang——Badong) Highway are taken as examples and analyzed by theoretical analysis and numerical simulation. Combining with the monitoring measurements in the construction site, the slope stability of shallow buried tunnels in high slope is analyzed and the treatment methods are studied. The contents are as follows.1. Based on the related references, the present methods of judgments and treatments for the slope stability are summarized.2. Based on the Sweden Strip Method which is quantitative for the slope stability judgment, a new mechanical model to evaluate the stability of high slope where the shallow buried tunnel portal is excavated has been proposed. This model has been applied in practical engineering, and the effectiveness has been shown by using finite element method.3. Numerical simulation is applied to the two different construction processes in which the construction order is different. Comparing the two schemes, it is shown that the optimum design is very important for the slope stability judgment.4. The surface displacements behind the retaining wall are analyzed and further predicted by Grey System Theory. It is shown that the treatments are effective to keep the slope stability for opening excavation of the high slope shallow buried tunnel. 5. A systematical method including the theoretical analysis, numerical simulation and monitoring measurement is applied in the analysis. It is more effective to judge the slope stability for opening excavation of the high slope shallow buried tunnel.