Study On The Technology Of Construction Of Small Spacing Tunnel Near The Existing Air Defense Tunnel

Along with the continuous development of railway construction, a large number appeared in the New Line was built beside the existing railway line project, and the increasing scale, due to the construction of double-track project by the geologic conditions and the comprehensive utilization of underground space needs. Therefore, the new tunnels near the existing tunnel due to the structural stability of the existing tunnel study have important significance and engineering applications.In this paper, Chongqing Rail Transit the first line Xiao-Jiao interval, which technology of construction of small spacing tunnel near the existing air defense tunnel as the research background.This article study that the existing air defense structure of the stability of surrounding rock, the two tunnels between the direct impact of the construction process and the middle rock pillar reinforcement.(1) The major studying is which analyzing tunnel construction process stress situation. I divided the three parts to illustrate:in a single cavity case; parallel and overlapping cavity situation; new line of existing excavation induced redistribution of internal forces. Through these three aspects analysis understand the two effects of changes in internal forces in the tunnel construction.(2) Exploiting FLAC3D software that Finite difference analysis simulate the Xiao-Jiao interval construction (6-6 section:mileage ZK1+962.029～ZK2+33.860). Simulated New Line Excavation impacting on the existing structure, the existing structure excavation impacting on the existing structure, the tunnel excavation impacting on the body of the middle rock pillar. The main construction of a new line above the existing structure and the new party line surface subsidence, both structural vault settlement and in surrounding structures supporting both internal force change; the existing structure excavation impact on the existing structure。(3) Study on the rock pillar which between the new lines and existing structures reinforcement body and blasting technique controlling. The short-distance tunnel in Xiao-Jiao interval the range of 6-6 section is used smooth blasting method. Moreover using peeling off layers by layers method carried out blasting process, which reducing disturbance to the surrounding rock. But the middle rock pillar will continue to be subject to greater disturbance, therefore, on the middle rock pillar reinforcement body is more important, the construction of this section mainly using the counter-pulled bolts grouting carried out rock pillar reinforcement, and use of the FLAC3D analysis software analyze the mutual influence which the new line excavation causing between the middle rock pillar and the existing structure after the middle rock pillar reinforcement.