积石峡水电站导流隧洞与中孔泄洪洞交叉段开挖支护方法

Excavation and support method for intersection of diversion tunnel and middle outlet tunnel of Jishixia hydropower station

积石峡水电站导流隧洞和中孔泄洪洞交叉段工程地质条件复杂,处在软硬相间的水平岩层中,且交叉段洞室断面大,两洞室交角小,是积石峡水电站地下洞室开挖施工中的最大难点。交叉段开挖施工措施采用了长台阶、分层分部位、短进尺、多循环的开挖方法,洞室支护措施主要采用锚喷支护加钢支撑的型式,洞室顶部还采用了预应力锚索和高强锚杆进行加固,并喷射钢纤维混凝土,钢支撑与锚索、锚杆之间均采用型钢进行焊联,与围岩形成整体拱效应。积石峡水电站导流隧洞交叉段开挖施工的顺利完成为提前截流提供了条件,争取了施工工期。

The intersection of diversion tunnel and middle outlet tunnel located in the horizontal layers of soft and hard rocks has complicated geological conditions. The tunnel section is big at the intersection, and the intersection angle of the two tunnels is small, which poses the greatest challenge in underground excavation construction of Jishixia hydropower station. The intersection is constructed by the excavation method of long benches, layer by layer and part by part, short advance and more circulation. The tunnels are mainly supported by rock - bolting and steel supports. The tunnel crown is strengthened by pre - stressed anchorage cables and high - strength rock bolts, and steel fiber shotcrete. Section steels are welded between steel supports, anchorage cables and rock bolts, forming integral arch effect together with surrounding rocks. The successful excavation of diversion tunnel intersection creates conditions for river closure ahead of schedule and saves construction period.