万安水利枢纽RCC溢流坝设计

Design of Wan'an RCC overflow dam

万安水利枢纽工程溢流坝，通过二期上游碾压混凝土的施工实践，并借鉴国内外设计施工经验，坝体采用ＲＣＣ、金包银防渗的方案，方量为４万立方米，该溢流坝业已完建。施工速度虽不算太快，１７７天浇筑３．１万立方米。由于采用高粉煤灰、低水泥用量的ＲＣＣ，混凝土温升小，加上采用薄层连续上升的施工方法，充分证明ＲＣＣ具有节省水泥、减少温控措施、节约工程投资等优点。万安ＲＣＣ溢流坝也产生过一些问题，主要是溢流坝上游面防渗层常态混凝土与ＲＣＣ结合面质量不好，８～１３坝块两种混凝土交界面发现有裂缝，钻孔压水，廊道内有漏水。连续上升时采取在缝面上布置骑缝钢筋，限制裂缝发展。虽然出现了一些问题，但已采取补救措施。

In view of the second stage Roc upstream cofferdam of Wan'an Project andthe experience in design and construction of RCC dam at home and abroad,the RCC dambody with conventional concrete facing was adopted for the overflow dam. The tolal RCC volume is 40 000m3. The temperature rise in the overflow dam is quite small because of RCC ofhigh flyash and low cement contents. The continuously rising of lifts was adopted for theplacement of RCC. Construction of the overflow dam shows that RCC does have advantagesof cement saving, temperature control measures reducing and cost economizing. However,there exists poor cohesion between RCC and conventional concrete facing at No. 8～No. 13dam blocks,resulting in cracking, with leaking into the gallery during borehole water pressure testing. After that,steel bars across the joints between RCC and conventional concretefacing were used to constrain the development of cracks.