Main diseases and prevention of tunnel
Main diseases and prevention of tunnel1 over excavation in tunnel excavationPhenomenon: in tunnel excavation, the upper, lower, left and right contours are exceeded.The reason analysis: the measurement is not allowed, the deviation is big; the hole position deviation is bigger; the hole in the hole drilling process does not have the straight hole to have the slanting hole to exceed the limit; the blasting parameter choice is wrong, the charge quantity is too much or unreasonable.Preventive measures: to ensure the measurement work turnover review system; accurate calculation of blasting parameters, the formal process test before entering the tunnel, timely adjust the parameters change of geological condition; hole position and direction control in drilling process.
Insufficient anchor tensionPhenomenon: anchor installation is not strong, pulling force is not enough.The reason analysis: anchor length is not enough; mortar grouting is not full; mortar wrapped anchor thickness is not enough or not at all; holes in the debris is not clean; the depth of the hole with the length of the bolt is not matching.Preventive measures: the hole diameter should be matched with the bolt diameter; strictly according to design deep hole drilling; grouting pressure and wind pressure water rinse perforations; bolt rust, straightening, ensure the bolt and hole center line on the same line of installation; the hole from the bottom of the hole, uniform and continuous. Midway not interrupt; using earlystrong medicine package bolt, the bolt diameter should be treated with perforation diameter matching.
Tunnel shotcretePhenomenon: the concrete spray layer and the rock surface is not bonded, concrete spray layer between the bond is not good.Cause analysis: the loose rock not clear spray surface; shotcreted rock debris is not scum washing or flushing thoroughly with wind pressure, water pressure; surface by spraying water, water, water concentration of untreated concrete spraying interval; before a layer of spray surface without wind, water washing scum. The air pressure is inconsistent with the spray distance.Preventive measures: remove the loose rock, clear surface by spraying of water, slag floating debris; water, concentrated water point of the surface by spraying with gouge, guide the drainage treatment of buried pipe; sprayed concrete before spray test, to determine the wind and spray distance coordination relationship between.
