The Stability Analysis On Pressure Tunnel Under Condition Of Complex Hydraulic

With the rapid development of the water conservancy industry, the phenomenon of mixed free-surface pressurized flow in hydraulic tunnel appeared and became more and more common. Along with the mixed free-surface pressurized flow, there is inhale and vortex, and they are bad for the operation of hydraulic structures. The problem about how to ensure the safety of the water diversion tunnel has become an important subject. Study on hydraulic characteristics and stability of diversion tunnel in the mixed free-surface pressurized flow is of great practical significance both on security and economic point of view.The topic of this article is “The Stability Analysis on Pressure Tunnel under Condition of Complex Hydraulic” based on the existing data about the study of mixed free-surface pressurized flow, taking the diversion tunnel of XUESHAN reservoir as an example, and using the FLUENT software to analyze the pulsation pressure, total pressure, velocity, vorticity changes and the direction changes, this passage defines the hydraulic characteristics of the diversion tunnel when it is in mixed free-surface pressurized flow. On this basis, it analyzes the flow characteristics of diverse tunnel water flow at different upstream water level and different inlet type combination. Then combined with practical engineering situation, we calculate the internal force distribution of the lining in diversion tunnel under different conditions, analyze the stability of the lining in diversion tunnel and finally proposed the method for reducing the adverse effect on the stability of tunnel lining from mixed free-surface pressurized flow to ensure the diversion tunnel has a long-term safe operation.By analyzing and calculating the simulation data, the main conclusions of the thesis are as follows:(1)Velocity distribution of the same cross section is in accord with the law of flow viscosity. The fluctuating pressure, the maximum flow rate and the flux of the water flow generated in the tunnel are decreasing with the depressing water level of upstream.(2)At the horn blast hole and the city-gate shaped tunnel joints, when the local velocity increases at the tunnel wall, the fluctuating pressure and the flux will increase locally at the same place.(3)By analyzing internal force of tunnel lining and displacement, we found that the internal water pressure is the biggest factor affecting reliability of internal force. When the water is under mixed free-surface pressurized flow, where the bottom close to the straight wall section, the local straight wall sections and the arch ends are not satisfied with the checking what shear strength and the maximum crack width. It’s paid us special attention to the tunnel supporting problem what the bottom, the straight wall and the connection with the top arch section are the most important to the diversion tunnel under mixed free-surface pressurized flow.(4)When the phenomenon of mixed free-surface pressurized flow in hydraulic tunnel appeared, negative pressure was frequently found in the bottom and the side wall of the tunnel, which results in great potential safety problem. Therefore we need to make good use of the landscape and geological conditions to avoid it.(5)For the diversion tunnel which can’t completely avoid the mixed free-surface pressurized flow, horn inlet can effectively reduce the flow pulsation pressure and reduce the negative impact of mixed free-surface pressurized flow.