Study On Tunnel Extension Technology

With the development of economy and traffic,the phenomenon of tunnel traffic jam becomes more and more serious.The expansion of existing tunnel has become one of the main methods of urban construction and development.In this paper,on the basis of summarizing the predecessors' research results,in the chengdu-chongqing high-speed liangshan-song at the engineering background of a tunnel,with the help of a finite difference numerical software FLAC3D5.0,for both the tunnel under the influence of seepage condition expansion method and different ways of expanding to dig for the influence of groundwater environment and protection,useful Suggestions are put forward.The main research work of this paper is as follows:?combined with the completed tunnel expansion project and the tunnel expansion project in the planning,the existing tunnel expansion methods are classified into four categories: in-situ expansion,small net distance expansion,in-situ expansion and small net distance expansion,combined expansion,double-arch tunnel expansion.The advantages and disadvantages of various expansion and excavation methods are analyzed.?Based on the chengdu-chongqing expressway middle liangshan-songjiagou no.1tunnel project,the paper compares and analyzes various expansion methods,and puts forward the most reasonable expansion method of "small net distance expansion +in-situ expansion".?Numerical method is used to analyze different excavation methods(deformation CRD method,three-step method and layer peeling method)for in-situ expansion under the influence of seepage,and the response and seepage change of surrounding rock and support of the tunnel under the three excavation methods are discussed.? In addition,in view of the shallow buried bias tunnel expansion of different ways,using flac3d5.0 on the surface of the tunnel settlement,surrounding rock stress and deformation,seepage effect of the change of analysis,discussed the characteristics and applicability of different expansion methods.?It analyzes the difference of surface settlement,vault displacement,plastic zone etc.of the tunnel under different seepage conditions in the expansion process of the tunnel;The effects of grouting thickness and different grouting effects on pore water pressure of surrounding rock are analyzed.