导流工程
River Closure — Gap Closure Operation
关工，导流洞已通水、河道已成功改道。水现在从隧洞走，上游围堰下游 的河床基本上干了。龙口还在——宽18米、流速4.2 m/s。最终合龙方案是什 么？
用立堵法两岸同时进占。策略分三阶段。第一阶段：用1到2吨块石推进、 把龙口从18米缩到约8米。第二阶段：龙口变窄流速升高——在龙口约5米时流 速会峰到大约6到7 m/s——改用5到8吨巨石。第三阶段：最终合龙时如果流速 超7 m/s，有15吨混凝土四面体备用、最后手段投放龙口。
我们有85辆自卸车循环——在上游3公里采石场装车、两岸各以90秒周期抛 投。两台推土机把抛投料往前推、在筑戗堤。每小时大约移动600 m³石料。
（合龙操作中）龙口剩6米——实测流速6.5 m/s。巨石稳住了但有些小的被 水冲走了——意料之中。加大巨石到最少8吨。剩3米……2米……最后一击！下最 后一串四面体——三个用钢缆连在一起！
龙口合龙了！河道已完全通过导流洞改道。让推土机立刻加堆石料加固截 流堤——加高到设计堤顶高程。然后开始基坑初期排水。大家干得漂亮！
Foundation Pit Dewatering and Cutoff Wall Inspection
Guan, the cofferdam is closed and reinforced. Now we need to dewater the foundation pit. The pit area is about 35,000 m², and the water depth inside the cofferdam averages 12 meters. That's roughly 420,000 m³ of water to pump out. What's your dewatering plan?
关工，围堰合龙加固完了。现在要抽干基坑。基坑面积约35,000 m²、围 堰内的平均水深12米。大约要抽420,000 m³水。排水方案是什么？
关工: We've installed 12 submersible pumps around the perimeter — each rated at 300 m³/h at a 15-meter head. Total pumping capacity is 3,600 m³/h. At that rate, the initial dewatering will take about 117 hours — roughly 5 days of continuous pumping. We also have 4 standby pumps in case any fail.
沿基坑周边布置了12台潜水泵——每台300 m³/h、扬程15米。总排量3,600 m³/h。按这个速率，初期排水约需117小时——大概连续抽5天。还有4台备用泵 以防有泵故障。
排水主管: The first 4 pumps are now running. Water level in the pit has dropped 0.5 meters in the first hour — that matches the calculation. The discharge water is being pumped into a sedimentation basin before it's released back to the river downstream — we need to control turbidity.
第一批4台泵在运转。坑内水位第一小时降了0.5米——与计算吻合。排水先 排入沉淀池后再放到下游河道——需要控制浊度。
(5 days later) The pit is dry except for some residual puddles. The final 2 meters of pumping took longer than expected because the pumps were fighting seepage through the cofferdam and foundation — about 800 m³/h of inflow.
（5天后）基坑干了，只剩一些残水洼。最后2米抽水比预期慢，因为泵在 对抗围堰和基础的渗水——约800 m³/h的来水量。
Now let's inspect the cutoff wall. The plastic concrete cutoff wall extends 40 meters into the alluvial foundation — that's well into the impermeable bedrock. I want to walk the exposed wall face and check for any defects.
现在检查防渗墙。塑性混凝土防渗墙深入冲积层基础40米——已深入不透水 基岩。到壁面上走一圈、查有无缺陷。
关工: (walking inspection) The cutoff wall face is clean and uniform. No visible joints, no honeycombing, no seepage stains. The wall was constructed in 6-meter panels using the tremie method — the joints between panels are tight. The piezometers behind the wall are showing zero pressure — the wall is effectively cutting off the groundwater flow. The foundation pit is ready for dam concrete placement.
（步行检查）防渗墙墙面干净均匀。无可见接缝、无蜂窝、无渗水痕迹。 用导管法分6米槽段施工——槽段间接缝紧密。墙后渗压计显示零压力——防渗 墙有效截断了地下水。基坑可以开始大坝混凝土浇筑了。