Research On The Application Of The Construction Technology Of The First Double Arch Tunnel

With the rapid progress of urbanization in our country,population density is growing especially in large city,traffic congestion has become one problems of the growing concerns and needs to be solved.Because of the features of fast, punctual and environmentally friendly, Metro become an important measure to solve the city traffic congestion. The urban rail construction project in our country, Shallow Excavation Method has been considerable development and application. In recent years, with the development of subway construction, more and more projects will encounter tunnels stop line and subway gateway construction. Tunnel parking line hasthe features of large, high risk and high cost, often using the current diversity of large cross section construction method, and the large section of the general construction with double side drift method, the CRD method, the side holes and other methods of construction. Compared with the large cross section multi-center construction methods, tunnel stop line as well as access line using arch tunnel is more appropriate. Currentlyarch highway tunnel often constructwith 3-heading excavation method and CRD Method, two city metro arched tunnel oftenconstructwith CRD Method. But both 3-heading excavation methodor CRD Method, there are long construction period, more process, high cost and low waterproof effect and other issues, the early support double-arch tunnel construction method as a substitute for the first two ways should come into being.This article combines the subway station excavation construction of Line 16 Wanping section, analysis of the applicability of the construction process early support double-arch tunnel. This article mainly analysis technical suitability by two aspects. On the one hand from the theoretical level, through numerical simulation, analysis the difference between double-arch construction method and the traditional construction method. It demonstrated the feasibility of the theory of double-arch tunnel consrtuction. On the other hand from the security level, the perspective of the construction site, excavatedepthlythe key point of affecting construction site safety of double-arch tunnel-the formation pre-grouting. Combining research and analysis Beijing poor geological, determine reinforcement difficulties and problems of the poor strata further of the characteristics and engineering properties. This aricle then focuses on the double-arch tunnel construction, grouting materials and processes for different adverse geology. From a security point of view to further improve the safety and reliability of double-arch tunnel construction method in Beijing area. The main results are as follows:First,stutythe theoretical analysis. By numerical analysis mechanical behavior of double-arch tunnel excavation and traditions common large-span construction method, application MIDAS-GTS, FLAC 3D, simulation analysis three-dimensional numerical, the following conclusions:1. Though the simulation analysis, construction site scheme adopted is reasonable and feasible;2. From the results of the simulation, the maximum deformation position generally occurs at the top and bottom of the separator and the tunnel.Second, the double-arch tunnel construction pre-reinforcing. Analysis the common special strata in Beijing, formation of the following conclusions:1. Determine the fine sand, sand, water bladders, and other types of cavity formation is Beijing Tunnels common adverse geologynow.2. Analyzed HPGM-fine cement slurry injection of fine sand grouting effect. Concidering through improved microfine cement slurry injection can penetrate reinforced fine sand, sodium silicate solution to the slurry injection intensity difference as well as ordinary cement slurry injection can not penetrate, and the problem of underground sand grouting consolidation provides new ideas and direction.