Numerical Simulation Analysis On The Soil Deformation Induced By Double Parallel Tunnel Construction

The city subway tunnels are usually excavated as double parallel tube tunnels at the same buried depth, and the space between the double tunnels is generally short distance. the soil deformation induced by double tube tunneling is more complex than single tunneling, the research on ground surface settlement and soil lateral displacement induced by double tube tunneling has important meaning.First, this thesis analyse the mechanism and the affect factors of ground surface settlement induced by shield tunneling, then using finite difference software—FLAC3D and embed in Fish language to compile programmes, to establish 3-dimension numerical model for single and double tube tunnel, The rules of the ground surface settlement and soil lateral deformation induced by its dynamic construction is studied. It include compare the rules of the soil deformation induced by single and double shield tunnel construction, as well as, analyse some factors affect soil deformation such as construction method,the time about grouting,soil pressure on cabin and so on. By the numerical simulation study, some useful conclusion as follows:(1) When the space between the double tunnels is short distance, the curve of ground surface settlement becomes the shape of " single apex ". The most settlement value is on the vertical axes of the two tube center connecting line, compare with single tunnel, its most ground surface settlement value and the width of settlement trough is about increased by 58 percent and by 16 percent; The most lateral deformation value is about 1 to 2 times of the value induced by single tunnel construction, the superposition effect is severe.(2) Double tube tunnel can excavated with synchronization and asynchronism, they have the same affect extension of the ground surface settlement on landscape orientation, the affect extension is about 10 times the width of the diameter of tunnel. the most ground surface settlement and soil lateral deformation have little difference.(3) When grouting on shield cauda is not in time, the most ground surface settlement value and lateral displacement is about 2 to 5 times of grouting in time, the affect extension of ground surface settlement on landscape orientation increased about 4m; The most transverse displacement move from the location of horizontal axes of double tunnels to ground surface. Grouting on shield cauda in time is a key factor to minish stratum loss.(4) In order to control the ground surface settlement and minish soil transverse displacement, increase soil pressure on cabin only play a finite role, or it is not appropriate at all, on the contrary, it can make the longitudinal soil deformation of tunnel inside and outside increased much. During the actual construction process, it should keep consistent with original soil pressure.