碾压混凝土坝小温差的中后期通水冷却
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摘要
通水冷却是减少碾压混凝土坝温度裂缝的主要措施,但通常后期冷却即在混凝土龄期120 d后快速降低水温,容易引起较大的自生应力和拉应力,小温差冷却可将中后期冷却开始时间提前,有效降低温度应力。但不同中后期通水冷却方式产生的温度应力相差较大,如何将小温差方式合理运用在坝体中后期冷却中需要精细分析。运用自行开发的浮动网格法三维有限元温控仿真程序对碾压混凝土坝的小温差中后期冷却方式开展研究。结果表明:当采用小温差的中后期通水冷却时,坝体温度和温度应力明显降低。当混凝土龄期结束后立即开始通水冷却,并且在中后期冷却时开展多档通水冷却,缓慢降低通水温度,可有效降低坝体温度和温度应力,为实际工程提供有利参考。
Water cooling is the main measure to reduce temperature cracks in RCC dams. But usually later cooling means reducing water temperature rapidly after 120 days of the concrete age may cause larger self stress and tensile stress inside the concrete. The small temperature difference cooling can advance the starting time of middle and late cooling stages, and reduce the temperature stress effectively. However, the difference of temperature stress produced by different middle and late stages water cooling methods is large. It is necessary to analyze precisely how to use the small temperature difference methods in the middle and late cooling stages of dams properly. The cooling methods of RCC dam in the middle and late stages is analyzed by using the self-developed 3-D FEM floating mesh method temperature controlling simulation program. Result shows that when the small temperature difference is used to cool the dam in the middle and late stages, the temperature and temperature stress of the dam reduced obviously. When the age of the concrete is over, the dam should be cooled immediately, several levels of water temperature should be set in the middle and late cooling stages, and reducing the temperature of the water slowly, which can reduced the temperature and temperature stress of the dam effectively. Study result will provide a favorable reference for practical projects.
Water cooling is the main measure to reduce temperature cracks in RCC dams. But usually later cooling means reducing water temperature rapidly after 120 days of the concrete age may cause larger self stress and tensile stress inside the concrete. The small temperature difference cooling can advance the starting time of middle and late cooling stages, and reduce the temperature stress effectively. However, the difference of temperature stress produced by different middle and late stages water cooling methods is large. It is necessary to analyze precisely how to use the small temperature difference methods in the middle and late cooling stages of dams properly. The cooling methods of RCC dam in the middle and late stages is analyzed by using the self-developed 3-D FEM floating mesh method temperature controlling simulation program. Result shows that when the small temperature difference is used to cool the dam in the middle and late stages, the temperature and temperature stress of the dam reduced obviously. When the age of the concrete is over, the dam should be cooled immediately, several levels of water temperature should be set in the middle and late cooling stages, and reducing the temperature of the water slowly, which can reduced the temperature and temperature stress of the dam effectively. Study result will provide a favorable reference for practical projects.
引文
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[11] 朱伯芳,吴龙坤,杨萍,等.利用塑料水管易于加密以强化混凝土冷却[J].水利水电技术,2008,39(5):36-39.
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[15] 国家能源局.混凝土坝温度控制设计规范:NBT 35092—2017[S].北京:电力出版社,2017.
[2] 段寅,胡中平,罗立哲,等.大型地下洞室衬砌混凝土温控防裂研究[J].水利与建筑工程学报,2015,13(4):107-110.
[3] 相昆山,张宏战,马震岳,等.寒冷地区碾压混凝土重力坝温控防裂研究[J].水利与建筑工程学报,2013,11(5):200-203.
[4] 朱伯芳,王同生,丁宝瑛,等.水工混凝土结构的温度应力与温度控制[M].北京:水利电力出版社,1976.
[5] 朱伯芳.大体积混凝土温度应力与温度控制[M].北京:中国电力出版社,1999.
[6] 刘俊,黄玮,周伟,等.大体积混凝土小温差的长期通水冷却[J].武汉大学学报(工学版),2011,44(5):549-553.
[7] 朱伯芳,张超然.高拱坝结构安全关键技术研究[M].北京:中国水利水电出版社,2010.
[8] 朱伯芳.论混凝土坝的水管冷却[J].水利学报,2010,39(5):505-513.
[9] 朱伯芳,吴龙珅,杨萍,等.混凝土坝后期水管冷却的规划[J].水利水电技术,2008,39(7):27-31.
[10] 朱伯芳,李王月,吴龙珅,等.关于混凝土坝基础混凝土允许温差的两个原理[J].水利水电技术,2008,39(7):21-26.
[11] 朱伯芳,吴龙坤,杨萍,等.利用塑料水管易于加密以强化混凝土冷却[J].水利水电技术,2008,39(5):36-39.
[12] 朱伯芳,吴龙坤,张国新.混凝土坝水管冷却的利与弊[J].水利水电技术,2009,40(12):26-30.
[13] Chen Yaolong,Wang Changjiang,Li Shouyi,et al.Simulation analysis of thermal stress of RCC dams using 3-D finite element relocating mesh method[J].Advances in Engineering Software,2001,32(9):677-682.
[14] 李守义,张金凯,张晓飞.碾压混凝土坝温度应力仿真计算研究[M].北京:中国水利水电出版社,2010.
[15] 国家能源局.混凝土坝温度控制设计规范:NBT 35092—2017[S].北京:电力出版社,2017.