现浇隧道裂缝控制大尺寸模型试验研究

Research on large-scale model testing of crack control in cast-in-place tunnel

针对太湖隧道主体结构混凝土不同步收缩和温度裂缝问题,提出不同步浇筑混凝土温度场自平衡系统技术方案,设计长×宽×高=10 m×5.1 m×6.65 m的大尺寸抗裂模型,采用有限元仿真计算结合温度应变监测研究其控裂效果。研究表明:提出的新老混凝土温度场自平衡系统,即利用后浇筑混凝土结构自身水化热通过水管联通加热先浇筑混凝土,在高温30~38℃环境下,使得模型侧墙混凝土温峰值降至46.6℃,绝热温升值降为19℃;底板温度升至39.0℃;新老混凝土结合面最大温差降至4.6℃,最大内表温差降至10.1℃;30 d内侧墙整体应变区域为(-60~180)με;持续监测6个月,仅1条长1.6 m、宽0.15 mm的裂缝产生;开裂风险大幅度降低。

To tackle asynchronous shrinkage and temperature cracks of the main structure of Taihu Tunnel,a temperature field self-balancing system of asynchronous concrete pouring is proposed and a large-scale crack-resistant model of 10 m(Length)×5.1 m(Width)×6.65 m(High)is designed to study the crack control effect with the finite element simulation calculation combined with temperature strain monitoring.The research shows that the proposed temperature field self-balancing system for new and old concrete,in which the hydration heat produced in newly-cast concrete structure was used to heat the previously-cast concrete via water pipes,decreased the peak temperature of the concrete in the side wall of the model down to 46.6℃when the high environmental temperature was between 30℃and 38℃,with a decrease of adiabatic temperature rise being 19℃.The temperature in the floor slab was raised to 39.0℃.The maximum temperature difference at the interfaces between the new and old concrete was reduced to 4.6℃,and the maximum inner surface temperature difference was reduced to 10.1℃.The overall strain area of the inner wall in 30 days was-60μεto 180με.With a continuous monitoring for 6 months,only one crack of1.6 m long and 0.15 mm wide developed,and the risk of cracking was greatly reduced.