Optimal Analysis Of Excavation Sequence And The Structure Of Shallow, Unsymmetrical Pressure, Twin-arch Tunnels

Excavation sequence and structure cross-section patterns of Shallow, twin-arch tunnels are one of the key links of engineering success of shallow,unsymmetrical pressure, twin-arch tunnels,This paper builds up FEM simulation model based on the geologic strata- structure method principle.Analyses & contrasts several common construction sequence and structure cross-section patterns of twin-arch, highway tunnel to finds out the best project,The project is more scientific & reasonable to the design of shallow,unsymmetrical pressure, twin-arch tunnels.This paper divides the two construction methods into 14 steps(contain a initial stress field), Contrasts stress fields, displacement fields and plastic areas of every procedure in two construction methods.,The results of this analysis show firstly constructing the shallow-covering side of shallow,unsymmetrical pressure, twin-arch tunnels is advantageous to the stability of the lining and the arrounding rock. It is very important to control displacement of arrounding rock and lining,especially prevent the mid-board from tilting and keep the lining from cracking during constructing twin-arch tunnels.The paper choose three kinds of adaptable twin-arch lining patterns (â‘ Straight board ,twin-arch liningâ‘¡Integrate bened board ,twin-arch liningâ‘¢Multiple bened board ,twin-arch lining) to build up FEM simulation models of shallow,unsymmetrical pressure, twin-arch tunnels, Contructing procedures of Every tunnel are divided into 14(16) steps based on firstly excavating the shallow-covering side.Those results of stress fields, displacement fields and plastic areas got from simulating analysis show that the bened board ,twin-arch lining is better than the straight board ,twin-arch lining. While, comparing two bened board ,twin-arch linings,we can find that stress concentration of the integrate bened board ,twin-arch lining is slightly serious than multiple bened board ,twin-arch lining and axis power is also slightly better.But the displacementof the lining and the plastic area of the arrounding rock are slightly smaller.From above analysis,in shallow,unsymmetrical pressure, twin-arch tunnels, The bened board ,twin-arch lining ought be adopted firstly,when the condition of arrounding rock is worse,Keeping arrounding rock stable must be put to the first,So integrate bened board ,twin-arch lining is suitable to this condition; when the condition of arrounding rock is better,the adopted lining ought be advantageous to bearing characteristic and stability,So the multiple bened board ,twin-arch lining can be used.The simulation results can reflect the real condition of shallow,unsymmetrical pressure, twin-arch tunnels and can be put into similar complicated underground engineering.