南水北调穿黄隧洞有粘结环锚预应力施工重难点分析

南水北调穿黄隧洞工程为我国首次采用盾构管片拼装式结构与衬砌预应力结构相结合的新型双层复合衬砌型式,隧洞内衬直径7 m,衬砌厚度45 cm,仅为直径的1/16,较常规混凝土偏薄,而且要承受单束锚索2 250 kN的张拉力,预应力偏高。为了解决薄壁混凝土环锚预应力施工中出现的锚具槽裂纹、钢绞线伸长值不足及预埋波纹管堵塞的难题,依托南水北调穿黄隧洞工程,采取理论分析计算、现场张拉试验等方法,探讨并解决了隧洞薄壁混凝土有粘结环锚预应力施工的技术难题,相关研究成果可供类似工程借鉴。

Key Points in Implementation of Bonded Circumferential Pre-stressing of Yellow River Crossing Tunnel on South-to-North Water Diversion Project

Yellow River Crossing Tunnel on South-to-North Water Diversion Project is the first tunnel in China where composite lining consisting of primary segment lining and pre-stressed in-situ-cast reinforced conerele secondary lining is adopted. The diameter of the secondary lining of tile tunnel is 7 m, while the thickness thereof is 45 era, i. c. , only 1/16 of the diameter thereof. Therefore, the pre-stressed in-situ-cast reinforced concrete lining of the tunnel is thinner than that in normal cases. On the other hand, one single anchor cable of the pre-stressed in-situ-cast reinforced concrete lining will undertake 2 250 kN tensioning force, i.e. , the pre-stress is higher. Under these conditions, problems, such as cracks of the anehor tool channels, insufficient elongation of steel stands and jamming of embedded corrugated pipes, may occur. In the paper, solutions for these problems are studied by means of theoretical analysis and in-situ tensioning tests. The paper can provide reference tor similar projects in the future.