向家坝水电站地下尾水主洞设计断面巨大，给开挖、衬砌和灌浆施工带来较大困难。为此，因地制宜地采用了不同于常规方案的“先挂顶，后下挖”的总体施工方案。该方案有效化解了衬砌和灌浆施工存在巨大高差的问题。同时，还在充分论证的基础上，在顶拱仅实施锚喷支护的情况下开展了顶拱两侧30°范围的无盖重固灌浆，从而降低了施工成本，缩短了施工工期。%The large design section of main tail water tunnel of Xiangjiaba Hydropower Station on Jinsha River brings signifi -cant difficulty for excavation , lining and grouting construction .In line with the local conditions , an initiative construction scheme of supporting tunnel top before excavating downward is proposed , which could effectively solve the problems of large elevation difference between lining and grouting construction .Moreover, based on the fully reasoning , the un-covering consolidation grou-ting was conducted in 30°of both side of the arch crown only after the completion of bolt -shotcrete support, which can save the cost and shorten the construction period .
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