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港珠澳大桥承台墩身采用全预制安装工艺,预制墩台结构尺寸大,属大体积混凝土施工范畴,为提高预制墩台质量,确保大桥120年的服役性能,在墩台预制过程中需严格控制大体积混凝土内外温度梯度带来的温度裂纹缺陷,为此对大体积混凝土的温度场进行模拟,对比预埋冷却水管与取消冷却水管两种不同工艺的裂缝控制情况。结果表明:预埋冷却水管最高温度降低7℃,最大温差降低了10℃;若取消冷却水管3d温度应力大于劈裂抗拉强度,存在开裂风险。现场监测数值结果表明:预埋冷却水管后NO.1、NO.3层最大温差均低于文献[5]中要求的25℃限值,NO.2层最高温差有超出25℃现象,据分析,NO.2浇筑完后冷却水管接通开始较晚,需在施工中根据现场实测温度情况及时通水,避免类似问题出现。
The pier block of Hong Kong-Zhuhai-Macao Bridge adopts fully-prefabricated installation process. The prefabricated piers have large structure and large mass concrete construction area. In order to improve the quality of prefabricated piers and ensure the service performance of the bridge for 120 years, The temperature crack caused by the temperature gradient inside and outside the mass concrete is strictly controlled. To simulate the temperature field of the mass concrete, the crack control situation of two different technologies, that is, the embedded cooling water pipe and the cooling water pipe being eliminated, is compared. The results show that the maximum temperature of the embedded cooling water pipe is reduced by 7 ℃ and the maximum temperature difference is reduced by 10 ℃. If the 3d temperature stress of the cooling pipe is canceled, it is risked cracking. The results of on-site monitoring show that the maximum temperature difference between NO.1 and NO.3 layers after the embedded cooling water pipe is lower than the 25 ℃ limit required in [5], and the maximum temperature difference in NO.2 layer has exceeded 25 ℃. According to the analysis , NO.2 pouring cooling water pipe connected to start later, the need to be under construction in the field temperature measured in real time through the water, to avoid similar problems.