Numerical Simulation Of TBM Construction Ventilation In Long Diversion Tunnel

The ventilation in the long diversion tunnel TBM construction is the complicated motion process involving the interaction of gases. The traditional ventilation design is based on one dimensional ventilation theory and the builder and designer's experience. Therefore, it is necessary to simulate the three-dimensional ventilation by Computer Fluid Dynamics (CFD), which can rationally optimize the parameters of construction ventilation and the allocation of resources, and it can supply the theoretical foundation for the construction ventilationThe steady three-dimensional RNGk -εventilation model is set up. There are some amendments in the model of turbulence dissipation rateε, which appropriately account for the effects of the anisotropic turbulence and non-equilibrium strain rate in the flow. The SIMPLE algorithm is used to solve the three-dimensional mathematical model.The simulated results were well in agreement with the experimental work on the pressed ventilation in a long tunnel by Huang Ruqin. TBM construction ventilation in the long diversion tunnel of Xinjiang eighty-one Daban was taken as a case. The 3D dynamic construction ventilation is simulated separately for diversion tunnel of 5km, 6.5km, 8km, 9.5km, 11km and 12.5km.The simulated results are as follows:(1) There are wall-attached jet zone, circumfluence zone and eddy zone in leading face. The air velocity in centre is larger than that near the wall far away from leading face. The air velocity and the turbulent kinetic energy are relatively larger near the ventage compared with those in the tunnel.(2) When the pressure difference between the air duct and tunnel is greater than a certain value, the air leakage rate is basically constant. Below the certain value, the air leakage rate increases in a logarithmic function along with differential pressure growth.(3) From the inlet of ventilation duct to the leading face, the air leakage rate decreases in a parabola manner. The quantity of air leakage reduces in a linear manner along the tunnel.(4) Air quantity and air velocity in ventilation duct decrease in a exponential manner along the duct to leading face. Air pressure in duct gradually reduces. Because of air leakage, air quantity and air velocity gradually increase from leading face to exit, and pressure gradually decreases. (5) By simulating 3D dynamic construction ventilation in the long diversion tunnel TBM construction, the design of ventilation system is rationally optimized.