大岗山高拱坝混凝土无裂缝成因的探讨

大岗山高拱坝坝址区地震基本烈度为Ⅷ度,100年超越概率2%,水平峰值加速度为557.5 gal,其混凝土裂缝控制技术是关键。大岗山拱坝建成后,混凝土无裂缝,坝体无渗漏,真正实现了拱坝混凝土无裂缝的目标。分析原因有以下两方面:(1)混凝土设计抗裂指数高、材料性能好,其设计抗裂指数为1.8,施工仿真计算结果达2.2以上;混凝土抗压强度高、弹模低、极限拉伸值大、绝热温升值低、徐变变形较大、自身体积变形较小。(2)仓面施工和温度控制达到了较高的质量水平,对于混凝土抗裂十分有利。

Discussion on reason of crack-free from concrete of Dagangshan High Arch Dam

The basic seismic intensity of the site for Dagangshan High Arch Dam is Ⅷ with the horizontal peak acceleration value of 557.5 gal for the exceeding probability of 2% in a period of 100 years，for which the concrete cracking control technology is the key link for the construction of the dam. After the complete of Dagangshan High Arch dam，no any cracks and leakages occur in the concrete，thus the objective of the crack-free from the concrete of the dam is truly realized. The analysis made on the reason shows that（1） the design anti-cracking index for the concrete is high with a better material performance. The design cracking index is 1.8，for which the simulated result is over 2.2，thus the concrete compressive strength is high with low elastic module，large ultimate tensile value，low adiabatic temperature-rise value，larger creep-deformation and small self-volume deformation；（2） the control of both the concrete placing face construction and temperature reaches to a higher quality level，which is quite favorable for the anti-cracking of the concrete.