硫酸盐侵蚀盾构隧道管片时变损伤特性及耐久性研究  

Time-varying damage characteristics and durability of shield tunnel segments under sulfate attack

作　　者：黄昌富 孙丹丹 郑太毅 刘中欣[1] 焦雷 周雄 Huang Changfu;Sun Dandan;Zheng Taiyi;Liu Zhongxin;Jiao Lei;Zhou Xiong(China Railway 15 Bureau Group Corporation Limited,Shanghai 200040,China;China University of Geosciences,Beijing 100083,China)

机构地区：[1]中铁十五局集团有限公司,上海200070 [2]中国地质大学,北京100083

出　　处：《土木工程学报》2024年第S1期128-133,共6页China Civil Engineering Journal

基　　金：国家重点研发计划(2023YFC3707804);中铁十五局集团公司科技研发计划(2022B5);上海市青年科技启明星计划资助(24QB2708000)。

摘　　要：盾构隧道长期处于腐蚀性海水或地下水环境中,硫酸盐侵蚀是造成管片混凝土损伤的重要原因。通过研究腐蚀环境中盾构隧道管片采用普通硅酸盐混凝土、掺合料改性混凝土,在5g/L,10g/L和50g/L不同浓度硫酸钠侵蚀溶液中混凝土质量变化率和线膨胀率随时间的变化规律,结合背散射电镜等微观手段,探究了管片混凝土结构特别是混凝土界面过渡区在硫酸盐侵蚀前后孔结构和侵蚀产物随侵蚀深度的变化过程,分析了掺合料对混凝土界面微观结构的改善作用,掌握了硫酸盐侵蚀环境下盾构管片混凝土结构的时变损伤规律。结果表明:管片混凝土在高浓度硫酸盐溶液侵蚀下,混凝土的线膨胀率明显高于低浓度硫酸盐侵蚀条件,侵蚀150-200天左右由于裂纹的生成侵蚀不断加速,膨胀率明显增大;矿粉和粉煤灰的加入对混凝土膨胀有显著的改善效果,膨胀率分别降低约16%和33%;根据背散射电镜结合EDS点分析结果,掺杂在水化硅酸钙凝胶孔中的钙钒石对混凝土膨胀性能具有直接作用,随着硫酸盐侵蚀反应的发生,C-S-H凝胶孔中的单硫型水化硫铝酸钙逐渐转换为钙钒石;由于钙钒石早期的填充作用以及后期裂纹的不断生成,混凝土表层的界面过渡区孔隙率随硫酸盐侵蚀先降低后逐渐增加。The shield tunnel is frequently subjected to corrosive marine or groundwater environments,and sulfate attack is a major cause of concrete damage to the tunnel segments.The research subjects are ordinary silicate concrete and admixture modified concrete in corrosive environments.The time dependent mass change and longitudinal expansion rate of normal concrete,concrete with fly ash and slag when immersed in 5g/L,10g/L and 50g/L Na,SO4 solution were investigated.And the influence of mineral admixture on the change of porosity and product composition in interfacial transition zone were also studied through microscopic analysis.The results show that the longitudinal expansion rate of concrete immersed in 50g/L Na,SO4 solution were higher than in low concentration,and increase significantly at 150-200d due to the formation of cracks,however,expansion rate decreased with the addition of fly ash and slag.It is also found that ettringite mixed with C-S-H gel influences concrete expansion directly.Based on the results of EDS spot analysis,AFm mixed with C-S-H change into AFt gradually.Due to the filling effect of ettringite and the continuous formation of cracks in later period,the porosity of the ITZ on concrete surface decreases first and then increases gradually.

关 键 词：盾构管片 混凝土 硫酸盐 钙矾石 损伤开裂 

分 类 号：U455.43[建筑科学—桥梁与隧道工程]