白佛隧道暗埋段混凝土水化热及分层控裂技术研究

Research on layering and crack control technology and hydration heat of concrete in buried section of baifo tunnel

白佛隧道为国内第一个双向十车道超宽截面隧道,对工程抗冻抗渗等耐久性提出较高要求,开展大体积混凝土控裂成为必要措施。在给定物理特性、热学参数和边界条件下,通过有限元软件计算白佛隧道主体结构暗埋段在采用不同分层浇筑工艺下水化热进程中的温度场,再结合相关理论计算其约束应力场,将抗裂安全系数作为评价指标对不同工况下隧道分层结构进行开裂风险分析,由抗裂安全系数临界值推算出不同工况下的最大浇筑长度和最长浇筑间隔时间。结果表明:三层浇筑工艺的最大浇筑长度为17.1m,单节段浇筑周期应控制在18d内,其中顶板应控制在6d内;双层浇筑工艺的最大浇筑长度为13.7m,单节段浇筑周期应控制在13d内。为降低结构整体开裂风险,提出在施工条件允许的情况下优先采用双层浇筑工艺建议。

Baifo Tunnel is the first two-way ten-lane ultra-wide cross-section tunnel in China, which puts forward higher requirements for durability such as frost resistance and impermeability of the project, and it becomes a necessary measure to carry out mass concrete crack control. Under the given physical properties, thermal parameters and boundary conditions, the temperature field of the buried section of the main structure of Baifo Tunnel in the process of hydration heat under different layered pouring conditions is calculated by finite element software, and the constraining stress is calculated in combination with relevant theories, The crack resistance safety factor is used as the evaluation index to analyze the cracking risk of the tunnel layered structure under different conditions, and the maximum pouring length and the longest pouring interval time under different conditions are obtained by calculation of the critical value of the crack resistance safety factor. The results show that: the maximum pouring length of the three-layer pouring condition is 17.1 meters, the single-segment pouring period should be controlled within 18 days,and the top plate pouring period should be controlled within 6 days;the maximum pouring length of the double-layer pouring condition is 13.7 meters, and the single-segment pouring period should be controlled within 13 days. In order to reduce the overall cracking risk of the structure, it is proposed to give priority to the double-layer pouring process when the construction conditions allow.