Impact Study Of The Existing Civil Defense Tunnel Influenced By The Excavation Of The Newly-built Tunnel

As China’s economy develops rapidly, more and more money has been spent ontransport facilities and constructions by our country. However, the traffic congestionphenomenon is increasingly severe because of the surge of city mobiles and buildingconstructions. So, the effective utilization of urban underground space becomes animportant trend of the future city development. Due to the confinements ofunderground buildings, geological conditions and route choices, the construction ofthe new tunnel may exert negative influences upon the existing architectures whenthey are very close to each other. Thus, how to reduce the negative impacts of the newtunnel excavation on the existing architectures and of the surface subsidence is asignificant research topic of the future city development construction.In the first place, the engineering classifications, research methods andconstruction measures of close-spaced tunnels are introduced. In the second place, thestress distribution and the stressing features of the tunnel support during theexcavation of proximity tunnels are briefly analyzed by the author. In the finality, byadopting the Midas GTS finite element mode to implement a three-dimensionalnumerical simulation on the construction process of this new tunnel which is veryclose to the existing civil defense tunnel in distance, the author analyzes the existingcivil defense tunnel’s deformation, the stress on the surrounding rocks, the surfacesubsidence and the regular deformation pattern of the new tunnel’s initial support.Because the existing civil defense tunnel is circle-like in shape and complex instructure and it shows up-and-down, juxtaposed, interlaced and crossed relationshipswith the new tunnel in space, the existing civil defense tunnel is divided into fourparts to discuss. Due to the existing civil defense tunnel’s complicated position anddifferent proximity degrees, a simulation on the new tunnel’s three headingexcavating process is implemented, attempting to prove the rationality of theconstruction unit’s excavating plan and excavating sequence. During the construction,predicting the key and dangerous areas of the existing civil defense tunnel will benefit increasing the risk awareness and analyzing the key constructing steps and the safetyof the initial support, will provide reasonable suggestions for design and constructionand references for similar engineering constructions.