Safety Control and Mechanical Response of Existing Tunnels Induced by Excavation of New Shallow Tunnel in Beijing

In crossing engineering, new tunnels’ section and construction methods are numerous, geological conditions are complex, and existing tunnels’ structure forms are various. New tunnels, geological conditions, and existing tunnels have a complex composition relationship which is no corresponding research. 18 sets of measured data from 13 projects in Beijing were found to summarize the construction methods of the new tunnels, analyses the existing tunnel’s deformation law and study the existing tunnels’ mechanical response by the two stage method. Research shows: (1) the new tunnels have three types of municipal pipelines, subway stations and metro tunnel. The new tunnel construction method have guiding hole method, bench method, cavern-pile method and center drift method. The corresponding relationship between the construction method and excavation area is clear. (2) The probability distribution of the existing tunnels’ maximum settlement accorded with normal distribution. The mathematical expectation is 4.89, and the variance is 16.4. The existing tunnels’ average maximum settlements are 2.56mm, 3.82mm and 11.07mm, which caused by excavation of municipal Pipeline, metro tunnel and subway stations. The research results can provide reference for similar engineering of new subway tunnels excavated beneath adjacent existing underground structures in urban areas.