长沙拱坝裂缝状况及寒潮影响的数值分析

1999年4月,广东省长沙拱坝在国内外首次成功应用外掺MgO混凝土不分横缝快速筑拱坝新技术。2000年1月拱坝下游面出现细小裂缝,宽0.2～1.2mm,深度2.2～4.4m,均未贯穿坝体上游面。基于氧化镁混凝土双曲线模型的数值仿真分析表明,设计条件下氧化镁混凝土的应力补偿量符合常规拱坝结构的应力状态,下游坝面裂缝与采用新技术无必然联系,保温板显著改善了下游坝面的应力状态。原设计坝体应力状态不理想,坝体工程混凝土质量造成抗裂性能降低,尤其是寒潮冲击时无有效的保温措施等因素引起长沙拱坝的裂缝。长沙拱坝坝体灌浆后目前已正常运用12年多。寒潮影响的数值分析为新技术应用研究提供了重要的基础资料,为类似工程提供有益的参考。

Crack state of Changsha arch dam and analysis on the effects of cold wave

Changsha arch dam in Guangdong province is the first arch dam in China and the world that was built with MgO-admixed concrete without transverse joint in April of 1999.In January of 2000,cracks of 0.2-1.2mm wide and 2.2-4.4m deep were found on the downstream surface of the dam,but none of them reached the upstream face.A 3D finite element simulation of hyperbolic model for MgO concrete shows that the actual concrete stress under the design MgO compensation is close to the state of conventional arch dam structure and that no link can be found between the downstream surface cracking and the use of new technology related to MgO concrete.The measure of heat preservation slabs is significant in improving the downstream surface stress.The analysis also reveals the main causes of cracking: the original design of dam stress was not ideal,concrete quality lowered crack resistance,and particularly,the heat preservation measure was not quite effective under cold wave impact in winter.Even so,the dam has been safely operated for over 12 years since the completion of its concrete grouting.The analysis of cold wave impact in this paper provides important information for promoting the use of new technology in other similar projects.