【作者】 吴超；

【导师】 潘坚文；

【作者基本信息】 清华大学 ， 水利工程， 2017， 硕士

【摘要】 溪洛渡拱坝坝高285.5米,在已建成的水电站中位列世界第三。溪洛渡拱坝位于西南强震区,所处地质条件复杂,水库蓄水后观测到谷幅收缩变形,因此,需要更深入研究溪洛渡拱坝抗震安全性能。高拱坝的强震非线性响应受多种重要因素影响,包括地基辐射阻尼、横缝张开、大坝-库水相互作用、混凝土损伤开裂等。论文采用清华大学拱坝-地基-库水系统非线性耦合分析模型,研究不同横缝模型、不同库水模型、谷幅收缩变形、混凝土老化等因素对溪洛渡拱坝抗震性能影响。取得以下创新性成果:1.进行了键槽理想和不考虑键槽两种横缝模型的比较研究。键槽理想模型认为键槽发挥完美作用,完全限制横缝的相对切向滑移。不考虑键槽模型认为横缝是平缝面,横缝的接触遵从库伦摩擦定律,可以产生相对切向滑移。键槽理想模型比不考虑键槽模型计算得到的拱坝非线性地震响应较小,表现为拱坝横缝开度减少,建基面和孔口处混凝土损伤范围减少。表明键槽作用可有效改善坝体整体受力状态,提高坝体抗震能力。2.考虑不同库水模型模拟地震动水压力,一种较为常用的方式是Westergaard动水附加质量公式,另一种则为可压缩库水单元模型。动水附加质量模型比库水单元模型计算得到的拱坝响应偏大,表现为拱坝横缝开度增加,上下游位移极值增加,坝体应力值较大,计算结果偏于保守。3.溪洛渡拱坝开始蓄水后,观测到谷幅收缩变形。首先,进行谷幅收缩变形简化模拟,分析拱坝静力条件下的响应。在此基础上,进行动力分析,研究谷幅收缩变形对拱坝抗震性能的影响。考虑谷幅收缩变形效应的拱坝地震响应增大,尤其是表孔坝段和建基面附近的局部损伤开裂范围和程度都会增加,表明谷幅收缩变形对于拱坝抗震性能不利。4.考虑拱坝在运行期间,混凝土材料发生老化,其力学性能的影响因素考虑为化学损伤和机械损伤。分析混凝土老化对拱坝地震响应的影响,结果表明,混凝土老化使得拱坝地震响应增大,表现为拱坝横缝开度增加,建基面和孔口处混凝土损伤范围扩大,部分坝段出现贯穿损伤开裂。此外,还研究了谷幅收缩变形和混凝土老化两种因素共同作用对拱坝强震响应的影响。随着运行时间增加,更多横缝发生较大开度,贴脚处损伤开裂范围增大。更多还原

【Abstract】 Xiluodu arch dam,which is 285.5m high,is the third largest dam in the world.Xiluodu arch dam is located in southwest of China,where the physical geography is very complicated and strong earthquakes occur frequently.After Xiluodu arch dam started impounding,valley width decrease is observed.The nonlinear seismic response of Xiluodu arch dam requires more research.Many factors,such as concrete damage cracking,radiation damping effects of foundation,joint opening and dam-water interaction,influent high arch dam seismic performance.Using dam-foundation-water nonlinear coupled model which is built by Tsinghua University,this study focuses on the nonlinear seismic response of Xiluodu arch dam considering influence factors like different joint models,different dam-water interaction models,valley width decrease and aged concrete.Some innovations are listed as follow:1.This study compares perfect keyway and no keyway.If the keyway is perfect in an arch dam,adjacent dam blocks cannot move tangentially.If there is no keyway in an arch dam,adjacent dam blocks can move tangentially according to Coulomb’s law.The nonlinear seismic response of Xiluodu arch dam with perfect keyway is smaller than that with no keyway,such as transverse joints aperture decrease and less damage near upper outlet or base surface.The keyway in arch dam improves effectively the stress state to have better seismic performance.2.Using different reservoir models is to simulate dynamic water pressure.Westergaard model is frequently used.The second reservoir model is semiunbounded reservoir model.The nonlinear seismic response of Xiluodu arch dam with Westergaard model,which is bigger than that with semi-unbounded reservoir model,is conservative,such as transverse joints aperture increase and the upstream or downstream extreme displacement increase.3.After Xiluodu arch dam started impounding,valley width decrease is observed.The valley width decrease is simulated with the monitoring result to analyze static state.Then more research is carried out to analyze seismic performance considering valley width decrease.Considering valley width decrease,the nonlinear seismic response of Xiluodu arch dam is higher.With the decrease in valley width,there is a corresponding increase in the nonlinear seismic response.To research seismic performance of Xiluodu arch dam,valley width decrease and more valley width decrease are considered.The decrease in valley width has negative impact for the arch dam seismic resistance,especially near upper outlet and base surface,where there is more damage.4.As the age of concrete increases,the concrete mechanical property will be lower with the chemo-mechanical damage.The nonlinear seismic response of Xiluodu arch dam with aged concrete is higher,such as transverse joints aperture increase and more damage near upper outlet or base surface.The nonlinear seismic response of Xiluodu arch dam with coupled model,which considers aged concrete and valley width decrease simultaneously in the first time,is higher,such as transverse joints aperture increase and more damage on the toe wall.更多还原