中老铁路友谊隧道石盐地层工程建设关键技术

Key Technical Problems of Youyi Tunnel in Halite Stratum on China-Laos Railway

中老铁路友谊隧道穿越石盐地层,含盐量高达80%,国内外罕见。为解决石盐地层隧道出现的隧底围溶蚀空洞、钢材严重腐蚀、衬砌开裂和底鼓等病害,保证施工与运营安全,通过实地调查、现场补勘、室内试验、数值模拟等方法,对石盐地层隧道防水体系构建、注浆堵水设计、氯离子侵蚀防治、结构选型和建筑材料研究等关键技术进行深入研究,结合现场监测和目前友谊隧道运营状态发现,整治处理取得了良好效果。研究结果表明:(1)探明石盐地层具有强溶解性、强侵蚀性、膨胀性的工程特性;(2)为限制地下水流动,避免石盐溶解,需采取全包防水措施,同时根据初支渗漏水情况分别采取隧底注浆、局部径向注浆和初支背后充填注浆;(3)针对超高浓度氯离子环境提出多道设防理念,设置素混凝土隔水层结构及两道卷材防水层;(4)通过结构比选,二衬推荐采用60 cm厚圆形衬砌结构,同时全段落衬砌结构取消洞室和各种加宽加高,降低结构防水难度;(5)为解决高强度等级混凝土易开裂问题,推荐隔水层结构采用C35聚合物混凝土,二衬采用C40低热混凝土。

China-Laos Railway Youyi Tunnel traverses halite stratum of up to 80 percent, which is rare at home and abroad. To solve the tunnel defects including tunnel bottom corrosion cavity, severe corrosion of steel, lining cracking and inverted arch cracking, the key technical issues of waterproofing system planning, grouting water plugging design, prevention of chloride ion erosion, structure selection and building material research are analyzed based on field investigation, supplementary exploration, laboratory test and numerical simulation. With on-site monitoring of current operation status of Youyi Tunnel, good results have been achieved. Research conclusions:(1) Halite stratum’s engineering characteristics include strong solubility, strong erosion and expansion.(2) To limit groundwater flow and avoid dissolution of halite, fully covered waterproofing measures are taken;grouting at the bottom of tunnel, local radial grouting and filling grouting behind initial support are employed respectively according to the water leakage of initial support in different parts.(3) In ultra high chloride concentration environment, multi-layer waterproofing conception is proposed, including one plain concrete waterproof layer structure and two coil waterproof layers.(4) Through structural comparison and selection, 60 cm thick circular lining structure is recommended for secondary lining, and chambers and additional widths and heights of various sizes are eliminated from full section lining structure to reduce the difficulties of waterproof structures.(5) To solve the cracking problem of high grade concrete, C35 polymer concrete is recommended for waterproof layer structure, and C40 low heat concrete is recommended for second lining.