特高拱坝封拱后温度回升及影响研究

Study on temperature recovery after arch sealing of super high arch dams and its influence

特高拱坝普遍存在封拱后温度回升现象。为清楚认识温度回升的原因、幅度、过程及影响,总结了特高拱坝内部封拱后温度变化情况,采用以后期水冷停水时刻作为起点的混凝土龄期,通过拟合及仿真反馈建立了大坝混凝土后期温升模型。以小湾拱坝为例,采用建立的后期温升模型进行仿真分析,结果显示：（1）后期温度回升主因是混凝土自身发热;（2）小湾拱坝后期温升明显,普遍有6~12℃,上升至最高温度约4~7年,回落至稳定温度约需40年;（3）考虑温度回升时大坝温度荷载与设计温度荷载存在差异,平均温度明显偏高,同时上下游温差减小;（4）后期温度回升使大坝存在整体向上游变形的增量,对坝体各向应力均有影响,坝趾产生拉应力增量,坝踵产生压应力增大,同时内外温差加大,在长期运行过程中可能会带来表面裂缝。

The phenomena of temperature recovery exist widespreadly in super high arch dams. In order to clearly understand the cause, range, process and influence, temperature changes after arch sealing of some typical arch dams are summarized. The temperature recovery models are built through data fitting and simu- lation methods, taking the age of concrete with the stop time of cooling water as its starting point. As an example, Xiaowan arch dam is analyzed with the built model. The results show that： （1）the main cause of temperature recovery is concrete hydration heat; （2）The temperature rise obviously in the later period of Xiaowan arch dam, generally 6-12 ℃, up to the maximum value with about 4-7 years and back to the quasi-stable temperature with about 40 year; （3）The temperature load considering temperature recovery is different from the design load, with a higher average temperature and a smaller difference between up- stream and downstream temperatures; （4）The whole dam has upstream deformation increment in consider- ation of the temperature recovery and all the stress is affected. There is tension stress increment in the dam toe and compression increment in the dam heel. Surface cracks may appear in the future because that the temperature difference is bigger than the design.