重力坝加高中减少结合面开裂措施的研究

Measures for reducing the cracking of the binding interface between fresh and old concrete in heightening of gravity dam

由于气温年变化及新老混凝土温差的作用,混凝土重力坝加高后,新老混凝土结合面绝大部分将被拉开,使大坝整体性降低。本文提出了在新混凝土内进行横向分缝并在下游面进行永久保温的防裂工程措施,使结合面开裂面积大幅度下降,超载条件下的坝体应力显著改善。文中研究了缝端应力集中问题,结果表明,年温度变化影响较大的深度只有5m左右。当横缝深度超过6m时,缝端应力集中不显著,横缝不致于扩展。

The most part of binding interface between fresh and old concrete in heightened gravity dam is always being dilacerated due to annual variation of atmospheric temperature and temperature difference between fresh and old concrete of the dam. The measures including setting up traverse joints in the new concrete dam block and placing thermal insulation material on downstream surface of the dam are suggested to reduce the probable cracking of the binding interface. The calculation result of applying these measures to the heightening project of the Danjiangkou Dam demonstrates that the cracking area of the interface is remarkably reduced and the stress status of the dam is obviously ameliorated. Further analysis shows that the depth in concrete affected by annual temperature is less than 5m and the stress concentration problem happened to the terminal of crack will alleviate if the depth of the transverse joints exceeds 6m.