Abstract:Research purposes: The causes of the blockage of blind drainage pipes in tunnels have not been thoroughly studied, resulting in the seepage and collapse of the weak part of the concrete lining of the second tunnel, which seriously affects the safe operation of trains. Therefore, the reasons for the blockage of blind drainage pipes in tunnels and how to control the blockage of blind drainage pipe in tunnel are studied. Research conclusions: (1) The blockage of blind drainage pipe of tunnel mainly comes from karst passageway, joint plane and bedding plane of tunnel, and it is the white powder of fine crystal particles in the initial stage when limestone and water produce heavy CaCO3, and it is collected by the hydraulic power of surrounding rock with a large amount. The secondary source is from the tunnel blasting and bolt construction, the fine-grained white powder attached to the cracks and surface of the surrounding rock of the tunnel, and the fine-grained white powder produced from the inside of the shotcrete, which are also collected by the hydraulic power of surrounding rock, and the quantity is less. (2) If the surrounding rock of the tunnel is not limestone and there is fine white powder in the blind drainage pipe, the main source is in the shotcrete. (3) Under the hydraulic action of the surrounding rock of the tunnel, mixing with all the fine white powder to form mixed water, one part of which passes through the surrounding rock to the outlet of the drainage pipe, the other part passes through the permeable layer of shotcrete and collects in the drainage blind pipe. (4) Because of the small diameter of drainage blind eye, the rate of discharging mixed water is reduced, and the white powder is deposited, which causes the drainage blind pipe to discharge unsmoothly and form blockage. (5) The prevention measures include water injection method for blasting hole, high pressure air blast method, special drainage channel, increasing the diameter of blind eye and blind pipe, increasing the outlet of blind pipe, not covering the blind pipe with geotextile, and paying attention to the construction quality of shotcrete. (6) The rate of mixed water discharged from the blind drain to the outlet should be the same as that imported into the front end of the blind drainage pipe. (7) The research results can provide reference for the prevention of blind pipe clogging in the field of railway and highway tunneling.
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