Analysis Of Stability And Study On Prevention Projects Of Slope On Tunnel Entrance At Yangpoli

When the tunnel is located in a bad geological body, collapse, unsymmetrical pressure and landslide are geological diasters which are often confronted in tunnel construction. Because the diseases are located in the portal section, normal construction would be diffcult, the construction costs would increase and the construction time would be delayed. In recent years, this type of diasters has been becoming more prevalent with the standards of highway, railway getting higher and the length and number of tunnel increasing. The project in tunnel entrance not noly belongs to the scope of the tunnel project, but also is closely related to the slope engineering, and its stability depends on the interaction of the slope and the tunnel. Therefore, the mechanism of interaction of the tunnel entrance slope and the tunnel has been of great concern for engineers and researchers.Taking the part of Wudu to Guanzigou of Lanzhou to Haikou highway as an engineering background, on the basis of qualitative analysis, the mechanism of interaction of the tunnel entrance slope and the tunnel in tunnel construction have been researched by using FLAC3D. The key research topics include the following aspects:1. The factors which affect the stability of slope on tunnel entrance and failue model of slope on tunnel entrance are analyzed with the method of engineering geological analysis. The factors which affect the stability of slope on tunnel entrance are summarized, and on this base, the causes of the slope disease were analyzed.2. The deformation and stress of the slope and the tunnel under natural condition were analyzed in the tunneling. By analyzing the changes of stress and deformation of the slope and tunnel, the deformation and the stress would be accumulated to a large extent. Final, this program is considered infeasible.3. When the tunnel is located in the poor geological body, slope disaster caused by tunnel lining crack has the following circular rule:the surrounding rock relax after the tunnel excavation, then slope slide and act on the tunnel lining, slope and tunnel interacct eachother to balance.4. By taking the measuers of prestressed anchor framework, the framework of micro-piles and the surrounding rock grouting, the deformation of the slope and tunnel are controled significantly in tunneling. Through analysis of the stress and deformation, the necessity of "slope reinforcement first, excavation in the second" is verified.5. On the basis of the calculation and analysis, a contrastive suggestion is posed. The conclusion comes by comparing with the original program, which is the nearby part of the top portal slope should be the focus of reinforcement.