糯扎渡水电站泄洪洞混凝土温控施工工艺

Temperature control technology of concrete of discharge tunnel of Nuozhadu Hydropower Station

糯扎渡水电站泄洪洞前期混凝土浇筑发生贯穿性温度裂缝后,通过采用中热水泥取代硅酸盐水泥、优化混凝土配合比和"差异化"通水冷却等措施,即在混凝土升温过程中产生压应力的时段,通大流量低温水,以加快混凝土降温速度,尽可能降低混凝土温度峰值;在混凝土温度峰值过后的降温阶段,为防止通水降温与表面自然降温叠加导致降温过快,而使混凝土产生开裂,严格控制降温速率,适度提高水温和降低流量,使后期浇筑的右岸泄洪洞抗冲耐磨混凝土未产生裂缝。其具体做法可供同类工程参考。

The penetrated temperature cracks were found during the early concrete construction of discharge tunnel of Nuozhadu Hydropower Station. To avoid temperature cracks in the later concrete placement, the measures such as moderate heat cement substituting for Portland cement, optimizing mixture ratio of concrete and differentiation water cooling were adopted. The differentiation water cooling is that when temperature rises and concrete compression appears, large amount water cooling is used to lower the temperature peak ; when temperature declines in later period, temperature decrease rate should be controlled, the wa- ter temperature should be increased and the discharge should be reduced, so as to prevent rapid cooling caused by superposition of water cooling and natural cooling. Therefore, no crack was found at the scour and abrasion resistant concrete of discharge tunnel at right bank.