Analysis Of Pre-reinforcing Technique For Tunnel Outlet In Area Of Shallow Metamorphic Loosen Rocks

In recent years, with the rapid development of China's national economy, highway construction has become the mainstream of China's road construction. However, qualification of highway is highly required, and need to overcome the influence of topographic height difference, digging tunnels in the mountains becomes an inevitable choice. With the influence of engineering geology, hydrogeology, human activities and many other factors, tunnel portals are usually shallowed and in partial pressure, rocks in tunnel portals tend to be poor characteristics and usually are hydrostratigraphic units. They are easily to be influenced by surface water, groundwater and rainfall. So it is very important to ensure the security of tunnel starting course of the hole tunnel construction.In order to study the deformation characteristics of tunnel and slope above tunnel entrance and give out the suitable per-reinforcements, this paper set in tunnels along the Xiarong line, Shuidu highway. Though topographic and geologic conditions stats of the tunnels, monitoring and measuring of typical tunnel portals'work progress, simulation and analysis of deformation characteristics and the suitable pre-reinforcements, the selection principles of pre-reinforcements are given out, which can provide reference for design of tunnel portals.In this paper, main tasks are as follows:â‘ Based on surrounding rock classification, slope gradient, transversal gradient, buried depth and Though topographic and geologic conditions stats of the tunnels along Xiarong line Shuidu highway are counted, then tunnel portals are divided into several types.â‘¡Based on the above classification and relevant engineering and research results, the things of different tunnel portal types need to focus on are pointed out. Thus the model is established. With the application of calculating software FLAC3D, the deformation characteristics of different tunnel portal types is analyzed, and the situations that needed pre-reinforcements are pointed out.â‘¢With the application of calculating software FLAC3D, the situations with pre-reinforcements are simulated. Then the pre-reinforcements selection principles in different conditions are given out with the effect comparative analysis among different pre-reinforcements and non-pre-reinforcements of tunnel portals.â‘£Though the analysis of typical engineering projects such as the left tube of Laozhai tunnel portal, the left tube of Ruipo tunnel portal, the left tube of Shangzhai tunnel portal and the right tube of Ruipo tunnel portal, results of simulation are verified and supplemented.