The Stability Analysis Of Pressure Tunnel Under Conditions Of Free-surface-pressurized Flow

Water diversion tunnel is a common water conveyance building,which is widely used in water conservancy projects.During overflow,the diversion tunnel may appear mixed free-surface-pressure flow,which affects the stability of the tunnel and even the whole project.The stability analysis of diversion tunnel always be a key problem in the research of hydraulic engineering field,so it is very necessary to study on hydraulic characteristics.In this paper,the cut and diverted water diversion tunnel project of the "Water source irrigation project of Xueshan Reservoir Tobacco Planting Areas in Weining County of Guizhou Province" is applied.According to the different flow states of the arched diversion tunnel and the different tunnel shapes in the tunneling process,the software is fluent in the fluid software.The turbulence two-equation RNG k-?turbulence model and VOF method simulate the flow field of the diversion tunnel in three dimensions to study the flow patterns,velocity distributions,and fluctuating pressure distributions in the tunnel under different conditions.At the same time,in order to further analyze the stability of the tunnel lining under the condition of free-surface-pressure flow,the internal force and displacement of the lining of the diversion tunnel of the project are calculated by using the software of Rational Geotechnical 5.6 software,and then the stability of the tunnel lining is analyzed to expect the tunnel to be in the water conservancy project.The following studies have provided reference for the further research on the emergence of the full-scale flow regime:(1)The pulsating pressure generated when the flow state of the gate tunnel is clear and full is much stronger than that generated when no flow occurs;the maximum flow velocity and the maximum pulsating pressure appear at the transition from the full flow to the open flow,and the local velocity of the tunnel wall and floor appears,pulsation pressure increase phenomenon.(2)The turbulent pressure generated by the circular tunnel under the condition of Ming-man flow is larger than that of the gate tunnel;the gate-shaped tunnel can better improve the flow state of the tunnel than the circular tunnel,reduce the pulsating pressure,and reduce the phenomenon of full-blown alternation in thetunnel..(3)The change law of axial force,shear force,and bending moment is basically the same in the two flow regimes of City Gate Tunnel.When alternating between Ming and Manchu,special attention should be paid to the lining support of tunnel entrances and transitions from full flow to clear flow.