引水系统
Headrace Tunnel — Drill-and-Blast and Concrete Lining
Tong, the headrace tunnel is a key structure in this project — 3.5 kilometers long, 8-meter excavated diameter. You're using drill-and-blast. What's the current progress and what are the main challenges?
童工，引水隧洞是这个项目的关键结构——3.5公里长、开挖直径8米。用钻 爆法。当前进展和主要挑战是什么？
童工: We've completed 2.8 km from the intake portal — that's 80%. The remaining 700 meters will break through to the surge tank shaft in about 3 months. The rock is mostly Class II granite — good quality, RMR around 65 to 70. Overbreak is well controlled — averaging 8 to 12 cm, which is within the 15 cm limit.
从进水口一侧已完成2.8公里——80%。剩余700米大约3个月贯通到调压井。 岩石主要是II类花岗岩——质量好、RMR约65到70。超挖控制得好——平均8到 12厘米，在15厘米限值内。
Your blasting pattern — what parameters are you using to control overbreak around the perimeter?
爆破参数——怎么控制周边超挖？
爆破工长: We use a carefully designed smooth blasting pattern. Total 78 holes per round. The cut area in the center uses 8 angled holes at 45°, 3.5 meters deep. The contour holes around the perimeter are spaced at 40 cm and use low-power emulsion cartridges — only 0.8 kg per hole compared to 2.5 kg for the stoping holes. We use non-electric detonators with 25-millisecond delays — the contour holes fire last, after the main blast has created the free face.
用精心设计的光面爆破布孔。每循环78个孔。中心掏槽区8个45°孔、深 3.5米。周边光爆孔间距40厘米、用低威力乳化药卷——每孔0.8 kg，对比崩 落孔2.5 kg。用非电雷管25毫秒延时——周边孔最后起爆，在主爆区造出临空 面后。
童工: After each round, we install the initial support within 4 hours. That's systematic rock bolting — 3-meter long, 25 mm diameter fully-grouted bolts at 1.5-meter spacing in the arch, plus 80 mm of steel-fiber-reinforced shotcrete. The permanent lining is 350 mm thick reinforced concrete, cast using a 12-meter-long telescopic steel form. We pour one 12-meter section per day. After the lining concrete reaches 70% strength — about 3 days — we do contact grouting through pre-installed pipes to fill any voids between the lining and the rock.
每循环后4小时内安装初期支护。系统锚杆——3米长、25 mm直径全粘结锚 杆、拱部1.5米间距，加80 mm钢纤维喷混凝土。永久衬砌是350 mm厚钢筋混 凝土，用12米长伸缩式钢模台车浇筑。每天浇一段12米。衬砌混凝土达到70% 强度后——约3天——通过预埋管做回填灌浆填充衬砌与岩石间的空腔。
Surge Tank Construction and Water Hammer Analysis
Tong, the surge tank is the safety valve of the water conveyance system. When the turbines reject load suddenly, the water column in the penstock decelerates rapidly, creating a pressure wave — water hammer — that can reach several times the static head. The surge tank absorbs this energy. Let's review the transient analysis results before we finalize the design.
童工，调压井是输水系统的安全阀。水轮机突然甩负荷时，压力钢管中的 水柱急减速，产生压力波——水锤——可达几倍静水头。调压井吸收这个能量。 我们在最终定设计之前过一遍瞬态分析结果。
童工: We ran the transient analysis using the method of characteristics for four load cases. Case 1: full load rejection of all three units simultaneously — the worst case. The maximum upsurge in the surge tank reaches 22.5 meters above the steady-state level, and the maximum downsurge reaches 15.3 meters below. The surge tank height — 85 meters total — provides a safety margin of about 25 meters above the maximum upsurge and 20 meters below the minimum downsurge. More than adequate.
我们用特征线法跑了四个工况的瞬态分析。工况1：三台机组同时全甩负荷 ——最严重工况。调压井内最大涌浪超出稳态水位22.5米、最大降浪低于稳态 15.3米。调压井总高85米——在最高涌浪上有约25米的安全裕量、最低降浪下 有约20米。完全足够。
What about the penstock pressure? That's what determines the wall thickness and the steel grade.
压力钢管的内压呢？这决定壁厚和钢级。
童工: The maximum transient pressure at the spiral case inlet reaches 2.95 MPa under Case 1 — that's about 1.64 times the static pressure of 1.8 MPa. We've designed the penstock for a design pressure of 3.1 MPa — a 5% margin above the maximum transient. The lower section of the penstock uses 32 mm thick high-strength steel plate, Grade 610 MPa yield strength. The upper sections use progressively thinner plate — 28 mm, 24 mm, 20 mm — as the static head decreases.
工况1下蜗壳进口最大瞬态压力达2.95 MPa——约为静压1.8 MPa的1.64倍。 压力钢管按设计压力3.1 MPa设计——高于最大瞬态5%的裕量。钢管下部用32 mm厚高强钢板、610 MPa屈服强度级。上部随静水头减小用逐步减薄的板—— 28 mm、24 mm、20 mm。
竖井施工主管: On the construction side, the surge tank shaft is now at 45 meters depth — more than halfway. We're using the raise-boring method. A 350 mm pilot hole was drilled from the top down using directional drilling to maintain verticality — the deviation at 45 meters is only 25 mm. Now we've attached the 3-meter diameter reamer head at the bottom and we're pulling it back up. After the 3-meter pilot is through, we'll widen to the full 20-meter diameter using drill-and-blast in 3-meter benches.
施工方面，调压井已到45米深——过半了。用反井钻法。从顶到底打了350 mm导孔，用定向钻进保持垂直——45米偏差仅25 mm。现在底部装上了3米直径 扩孔钻头、正在反拉上来。3米导井贯通后，用台阶钻爆法扩挖到20米全直径、 每阶3米。