二期围堰泄流槽体型及开挖施工技术

某水电站二期围堰受客观条件限制难以全部拆除至设计高程, 故在明渠截流前, 先在二期围堰上开挖泄流槽 导流。截流模型试验结果表明, 为增大泄流槽的分流比, 降低截流落差, 应尽可能降低泄流槽底高程; 若向下深挖施 工困难, 可以扩宽泄流槽。施工过程中, 通过分区开挖围堰、一次性爆破防渗墙至设计高程、在防渗墙下游超挖水力 冲刷堆碴坑等措施, 尽可能深挖泄流槽。 Due to that the demo lition alt itude is hard to reach under pr act ical limitations, a div ersio n tr ench was excav at ed on the second2stag e cofferdam to div ert w ater befo re the o pen div ersio n channel clo sure of a hydro power station. The hydraulic clo sur e model test results indicated that the shape of div ersio n trench affects the difficult y of t he closure, and r educing the bottom eleva2 tion of t he diver sion trench is essential to r educe the closure dr op and increase t he diversion r atio of tr ench. If deep ex cavation is har d to conduct, an alter nat ive is to increase the bo ttom w idth of diver sion t rench. Dur ing the constructio n, sever al measur es wer e adopted to dig the diver sion t rench as deeply as possible, including ex cavatio n in differ ent parts, blasting diaphr agm wall to the design altitude at o ne time, and ex cavating a hy dr aulic scour pit behind the diaphr agm w all.