汶川地震中宝珠寺重力坝地震响应的三维有限元模拟

汶川地震中宝珠寺水电站遭受的地震烈度为8°(相当于水平峰值加速度0.2 g),远超过大坝的设计地震水平(0.1 g),震后大坝未见明显震损.为解释大坝在地震中的抗震现象,构建了坝址区三维模型.考虑坝体横缝非线性以及三个方向地震作用的不同组合方式,对汶川地震中大坝的动力响应进行有限元模拟.在此基础上,针对震后提高的抗震设防标准,进一步选取典型坝段,采用二维弹塑性方法对大坝进行抗震复核并分析可能的破坏模式.模拟结果表明:横河向地震分量起主导作用而顺河向地震作用相对较弱是宝珠寺重力坝在汶川地震中免于发生损坏的主要原因.坝顶混凝土发生挤压破碎缘于永久横缝在地震中高频渐开渐合行为引起的剧烈碰撞.宝珠寺重力坝对设计地震0.27 g的强震可以保持整体的安全性,对校核地震0.32 g的强震整体安全性降低,水库正常运行及抵抗余震的能力将受到影响.

3D finite element modeling of seismic responses of Baozhusi gravity dam in Ms 8.0 Wenchuan Earthquake

Baozhusi gravity dam was not destructively damaged during the MS8.0 Wenchuan Earthquake even though the earthquake intensity(0.2 g) at the dam site exceeded the design level of the dam(0.1 g).In order to analyze the dam′s performance to resist the earthquake,we design a three-dimensional model to simulate the dam′s dynamic responses with finite element modeling scheme with consideration of the nonlinearities of contraction joint opening and different combination patterns of three-component seismic processes.Then with 2D elasto-plastic yielding analysis technique we reassess the seismic safety and discuss the possible destruction modals of the dam during strong earthquake with updated seismic fortification levels.The results demonstrate that(1) the transverse component of earthquake motion predominates in the dynamic responses of the dam,and the stream component has relatively weaker excitation to the dam,which is probably the reason that the dam luckily avoided strong damage in the Wenchuan Earthquake.(2) The concrete fracture occurred near the permanent contraction joints at the top of the dam may have resulted from the impact of concrete blocks during joints opening.(3) The dam safety can meet the requirement under the updated design earthquake(0.27 g) and will be lower under the maximum credible earthquake(0.32 g),which may affect the reservoir operating and the resistant abilities to aftershocks.