隧道衬砌施工缝抗渗性及影响因素室内试验研究

Experimental Research on Impermeability and Influencing Factors of Tunnel Lining Construction Joints

为研究止水带、界面剂和界面粗糙度等因素对衬砌施工缝抗渗性的影响,提高富水隧道衬砌抗水压能力,通过剖析隧道衬砌施工缝防水构造,找出影响其抗渗性能的关键因素。设计室内抗渗试验,制作162块施工缝抗渗试件进行各因素敏感性分析并揭示其作用机制。试验结果表明:1)浇筑时间间隔超7 d的施工缝会导致混凝土抗渗性降低2~3个数量级,其抗渗性取决于新旧混凝土界面和止水带与混凝土界面的抗渗性能;2)缩短浇筑间隔和涂抹界面剂有利于降低新旧混凝土界面的渗透系数;3)通过凿毛处理增加施工缝界面的粗糙度对施工缝抗渗性无明显提高作用,甚至由于过度凿毛损伤混凝土基体引起界面抗渗性降低;4)在界面浇筑间隔7 d且无凿毛条件下,橡胶止水带与混凝土界面平均相对渗透系数是新旧混凝土界面的47.5%,其抗渗性优于施工缝新旧混凝土界面,其止水机制为降低界面渗透系数、提高单位渗流长度的水头损失和延长渗流路径长度共同发挥作用;5)钢板止水带与混凝土界面的渗透系数近似等于施工缝新旧混凝土界面,其止水机制为通过延长渗流路径长度发挥作用。

To investigate the impact of factors such as waterstops,interface agents,and interface roughness on the impermeability of tunnel lining construction joints,and to enhance the water pressure resistance of linings in water-rich tunnels,the waterproof structure of tunnel lining construction joints is examined to identify the crucial influencing factors of their impermeability performance.The research includes designing and performing indoor impermeability tests on 162 specimens to conduct a sensitivity analysis of various factors and elucidate their mechanisms of action.The findings demonstrate that:(1)Construction joints with pouring intervals exceeding 7 days exhibit a decrease in concrete impermeability by 2 to 3 orders of magnitude,influenced by the impermeability at the interface between the new and existing concrete,and between the waterstop and concrete.(2)Reducing the pouring interval and applying interface agents effectively lower the permeability coefficient at the interface between new and existing concrete.(3)Enhancing the roughness of the construction joint interface through chiseling does not significantly improve impermeability;excessive chiseling,in fact,diminishes it.(4)With a pouring interval of 7 days and no chiseling,the average relative permeability coefficient at the interface between the rubber waterstop and concrete is 47.5% of that at the interface between new and existing concrete,indicating superior impermeability in construction joints.(5)The permeability coefficient at the interface between steel plate waterstops and concrete is approximately equal to that between new and existing concrete,functioning to extend the seepage path length.