长大软弱围岩隧道湿喷混凝土回弹率控制技术

Rebound Rate Control Technology of Wet Shotcrete in Long and Weak Surrounding Rock Tunnel

文章以贵南铁路九万大山一号隧道工程为背景,在山岭隧道围岩异常复杂工况下,为克服C25湿喷混凝土回弹率过大的通病,通过试验寻求水泥、粉煤灰、减水剂、速凝剂等掺和料的最佳配合比,并加入硅灰、SBT-N(Ⅱ)速凝剂、SBT-HDC(Ⅱ)C25湿喷混凝土纳米掺和料等新型建材,控制混凝土坍落度和喷射厚度,选取合适的湿喷距离和湿喷角度,不仅有效降低了C25湿喷混凝土的回弹率,还有效提升了混凝土一次湿喷厚度,实现了降本增效。

Jiuwandashan No.1 Tunnel Project of Guiyang-Nanning Railway is adopted as the background in the paper.The best mixture ratio of cement,fly ash,water reducing agent,accelerating admixture and other mineral admixtures is sought through experiments in order to overcome the common problem that the rebound rate of C25 wet shotcrete is too high under the extremely complicated working condition of surrounding rock in mountain tunnels.Silica fume,SBT-N(II)accelerating admixture,SBT-HDC(II)C25 wet shotcrete nano-admixture and other new building materials are added to control concrete slump and spraying thickness.Appropriate wet spraying distance and wet sprayingangle are selected,thereby not only effectively reducing the rebound rate of C25 wet shotcrete,but also effectively improving the thickness of once wet shotcrete.Cost reduction and efficiency increase are achieved.