Study On The Construction Technology And Stability Of The Portal Section Of The Tunnel With Shallow And Bias Pressure Soft Surrounding Rock

In the process of tunnel construction in mountainous areas,due to the existence of shallow burial,bias and other adverse geological conditions,it is very easy to cause engineering accidents such as large deformation and collapse of the tunnel,which not only causes the loss of people’s lives and property,but also greatly affects the construction safety of the whole tunnel.So this article in guizhou is swan point xi highway tunnel as the backing,the theoretical summary,numerical simulation and field monitoring measurement method,in view of the shallow bias tunnel in weak rock hole construction technology in the process of the excavation and the stability of the tunnel are studied,the main research contents and research results are as follows:(1)This paper systematically analyzes the geological characteristics of shallow buried biased soft surrounding rock tunnel and the influence of adverse geological conditions on the construction of the opening section,and summarizes the means and measures to eliminate the bias effect of the opening section,the excavation method of the tunnel,the supporting method in the tunnel and its applicable characteristics.(2)combined with the actual engineering situation,based on the continuum of stratigraphic structure method,double wall pilot tunnel were analyzed by using numerical simulation method,CRD method,reserve ring core method and CD method in different construction methods of tunnel surrounding rock displacement and stress of the surrounding rock stress and the initial supporting structure,and considering the tunnel construction safety,construction difficulty,construction period and construction of economy and so on various aspects of difference,concluded four construction technique can satisfy the requirements of the tunnel construction safety,but reserve ring core method on the construction difficulty,construction period,construction economy have more advantages;The best excavation method for the shallow buried bias section of swan cave tunnel hole is the ring-reserved core earth method.(3)based on the annular core reserved excavation method,using numerical simulation software,MIDAS/GTS for the shallow bias tunnel in weak rock stability influence factors are discussed,by adjusting the left and right hole excavation sequence constraints as well as the left and right hole spacing,further analysis of the displacement of surrounding rock during the process of tunnel construction,stress state of surrounding rock and the characteristics of stressed deformation of retaining structure in the early,get the swan hole tunnel in annular reserved core construction method and the most reasonable excavation process constraints spacing.(4)combined with field monitor measuring the vault sink hole section,peripheral convergence,and the surface subsidence data,it is concluded that shallow bias tunnel in weak rock displacement of surrounding rock during the construction of the changing rule of the curve,and compared with the results of numerical simulation analysis,validate the hole section ring reserved core excavation scheme of rationality and accuracy of the method,and to provide effective technical support for the similar projects.