浅谈西河水电站埋管段破碎洞段的砂浆喷层支护

Shotmotar Support in Breaking Hole in Buried Pipe Section of Xihe Hydropwoer Station

西河水电站浅埋式压力管道中平段，设计开挖洞形为圆形，直径4．1m．洞室轴线位于断裂破碎带，周边围岩破碎，属Ⅳ～Ⅴ类不稳定围岩．开挖洞室时坍方严重，虽采取了传统的木支撑和钢支撑措施，但效果差，严重影响施工进尺．最后采用了砂浆喷层支护，控制了洞室坍方问题．该方法主要是利用喷射机将搅拌好的喷料，按一定厚度、时间间隔，采取先边墙后项拱的方式，循环喷射开挖面，以达安全支护的目的．另外砂浆喷层支护在施工中注意了如下因素：（1）拌和质量；（2）风、水压的匹配；（3）速凝剂添加量等．

The designed cave shape for excavating of midlevel segment of shallow buryingtype pressure line of Xihe hydropower station is circular. The diameter is 4. 1 meters. The axis of the cave is located in a fault zone. Its surrounding rock is broken and belongs Ⅳ to Ⅴ unstable rock. When excavating, landsliding question was serious. Traditional wood-prop and steel-prop was first taken for it. But effect was bad and construction program was hold up. Finally shotmortar support was taken. This method successfully controlled cave landsliding and solved the problem of construction safety. The way is mainly by shooting excavated surface to safe prop by shotcrete machine with mixed material, at regular time and thickness interval, from side walls to dome. For assuring quality of shooting layer and lowering ratio of elastic rebound, following factors should be noted in construction on shofmortar support: mix quality.pressure dispose of wind and water and additon quantity of set-accelerator.