Experimental Study on Lining Crack Repair with Geopolymer-cement Composite Material in Highway Tunnel
To investigate the effect of geopolymer on tunnel lining crack repair and the influencing factors involved,the experimental study is carried out by using a simulation platform for crack diagnosis and treatment in tunnel lining structures.Based on the stress characteristics of horseshoe-shaped lining of highway tunnel,a platform is used to simulate lining profile through two arch steel frames.By rotating the steel frames around hinge support,the non-uniform tension of crack repair on section is achieved.Tests on crack repair under stable state,developing state,and different leakage conditions are conducted on this platform.The evaluation is based on the stress distribution and paste distribution of section after opening to assess the actual repair effects of 3 materials of pure polymer,pure cement mortar,and cement+polymer.The study analyzes the influence of different material combinations,lining crack conditions,and water leakage on repair effects,and provids relevant engineering recommendations.The result indicates that,as an alkali activator,the cement can react with polymer materials.The crack repair effect of cement+polymer is superior to pure cement mortar or pure polymer.The crack repair effect of cement+polymer composite material weakens as the opening loading rate increases.The bonding tension stress under a loading rate of 30 N/h is 46%of that under 10 N/h,and only 40%under no tension conditions.It is recommended to carry out repair work after the lining crack is basically stable.The repair effect of cement+polymer composite material weakens as the leakage amount at crack location increases.The effect of water seepage(1 ml/min)on repair is relatively small,with repair effects decreasing by 22%and 19%at 7d and 28 d respectively,allowing direct crack repair.Under gushing water conditions(20 ml/min),the repair effects at 7 d and 28 d decrease by 42%and 38%respectively,making direct repair inadvisable.
tunnel engineeringcrack repaircrack diagnosis and treatment platformgeopolymer-cement composite materiallining crack
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