闸墩内部水管冷却和表面保温措施的抗裂作用研究

本文针对闸墩施工期混凝土易开裂的问题，分析了闸墩在施工期混凝土的开裂原因，说明了采取闸墩内部水管冷却和表面保温两种不同温控措施的防裂机理与效果。指出单纯表面保温措施能虽够减小闸墩早期内外温差和表面拉应力，却使得混凝土的温升和温降幅度加大，闸墩冷缩期内部拉应力显著增加。于是提出内部水管冷却和适度表面保温相结合的闸墩温控防裂新思路，并已在姜唐湖泵送混凝土退水闸工程中得到应用，严寒季节施工的所有16孔闸室泵送混凝土都没有开裂，收到了较好的防裂效果。

Effect of internal cooling pipes and external heat preservation on prevention from concrete cracking during construction of sluice pier

The cause of concrete pier cracking in the period of construction is investigated by numerical analysis, and the effects of internal water-cooling pipe and external heat preservation measures on preventing from cracking are analyzed respectively. It is found that the external heat preservation measures can reduce the temperature difference between surface and internal concrete of the pier as well as the surface tensile stress at the early age, but the amplitude of temperature fluctuation increases, which results in the remarkable increase of internal tensile stress in the later age. The adoption of watercooling pipes combines with reasonable external heat preservation achieves .the best result in temperature control for preventing cracking. This concept is accepted and realized in the construction of the Jiangtanghu sluice project. No cracking happen to all piers constructed in cold season.