Study On Seepage Characteristics And Watertight Of Flexible Joint Section Of Hydraulic Tunnel Passing Through Active Fault

There are many large-scale diversion tunnels in the west of China,some of which pass through the active fault,interlayer dislocation zone and other adverse geological conditions.Once the fault occurs and lives,it is likely to cause large deformation of the tunnel section passing through the fault and even damage the tunnel structure.Therefore,it is necessary to adopt relatively reliable flexible connection to connect the tunnels on both sides of the active fault zone so that the tunnel will not break due to fault activation during operation.So,what kind of flexible material to connect and how to connect is an important scientific and technological problem in engineering.In view of the above problems,this paper takes the joint of flexible connection section of a hydraulic tunnel crossing active fault as the research object,obtains the change rule of macro mechanical strength of the connection material through the anchorage length test research of the connection material(polyurea elastomer),and then obtains the anchorage length of the required connection material;through the penetration damage test research of the joint of flexible connection section The change rule of permeability coefficient,wave velocity,porosity and micro structure with the increase of osmotic pressure is obtained,and the mechanism of Seepage Damage at the joint of flexible connection section during the operation of hydraulic tunnel is revealed.Based on this,the water sealing measures suitable for the joint of flexible connection section of hydraulic tunnel are proposed,and the water sealing effect is evaluated through experimental research,which is the joint of flexible connection section of hydraulic tunnel.The setting of water stop at the site provides scientific basis.The specific research contents and achievements are summarized as follows:(1)The results of the center pull-out test show that the specimens with anchorage length of 5D and 8D will be pulled out completely and the specimens will be destroyed in the test;for the specimens with anchorage length of 10 d,only a small part of the bond between the reinforcement,polyurea elastomer and concrete will fail,but the overall strength can still play a better role;(2)Compared with 0.5MPa osmotic pressure,the joint of flexible connection section of hydraulic tunnel increases 11.32%,24.53% and 30.19% respectively under 1.0MPa,1.5MPa and 2.0MPa osmotic pressure;under 0.5MPa,1.0MPa,1.5MPa and 2.0MPa osmotic pressure,the wave velocity decreases 1.58%,5.48%,10.21% and 13.79% respectively,compared with the sample without osmotic test,and the porosity decreases 1.58%,5.48%,10.21% and 13.79% respectively The results show that the porosity and fracture increase with the increase of osmotic pressure.(3)The damage of the joint of the flexible connection section of the hydraulic tunnel is caused by the expansion of the original micropore and the development of the crack due to the increase of the seepage pressure.With the gradual expansion of micropores and the development of cracks,a seepage channel is formed at the connection part of concrete and polyurea elastomer,and the water flow continues to penetrate along the seepage channel,which may lead to the decrease of the tightness of the connection between concrete and polyurea elastomer,and then the joint of the flexible connection section will be damaged,affecting the normal operation of the hydraulic tunnel.(4)After setting water stop by slotting the joint material(polyurea elastomer)and the concrete surface,the increase of the permeability coefficient of the sample decreased obviously;compared with the sample before penetration,the wave velocity decreased by 1.01%,2.22%,2.89% and 3.86% respectively,and the porosity increased by 1.20%,3.11%,6.48% and 8.40% respectively;compared with the sample without water stop,the decrease of the wave velocity and the increase of the porosity decreased significantly All of them slowed down obviously,and the microcracks and micropores in the sample decreased obviously.(5)By slotting the joint material(polyurea elastomer)and the concrete surface,the water stop can make the concrete and the joint material embedded in each other;it can also greatly extend the seepage diameter of the seepage flow,reduce the seepage pressure acting on the joint,and finally slow down or even prevent the damage.