四川泸定Ms6.8级地震大岗山特高拱坝变形特征分析

Deformation characteristics analysis of Dagangshan super high arch dam in Sichuan Luding Ms6.8 earthquake

大岗山双曲拱坝坝高210 m,坝址位于鲜水河、安宁河和龙门山三条断裂带交汇处附近,其抗震设防加速度为557.5 cm/s^(2),是世界上抗震设防标准最高的高拱坝。在泸定Ms6.8级地震中,大坝强震监测系统记录到了完整的地震波形,且顺河向最大峰值加速度达到586.63 cm/s^(2),是目前国内已建200 m级高拱坝中唯一经历近场强震考验的大坝。依据大坝震后变形宏观现象和监测原观数据,对大坝坝体与地基系统变形进行了分析。结果表明:震后大坝整体向下游变形,径向位移增量在-1.53~20.04 mm之间,弦长拉伸增量在15.27~23.50 mm之间,大坝横缝在地震过程中存在开合过程,低高程横缝存在一定残余张开,增量在-0.08~0.46 mm之间,变形整体协调。同时,大坝左右岸坝肩、坝基置换块、大坝与基础等部位存在一定的残余错动,这是导致大坝产生较大残余变形的主要原因,但大坝坝体本身仍处于弹性工作状态,最终在新的平衡位置上保持稳定,表明大岗山拱坝经受住了本次强震考验。相关成果可为震后大坝安全评估、高拱坝抗震设计及研究提供参考。

Dagangshan double-curvature arch dam is^(2)10 m high.The dam site is located near the intersection of Xianshui River,Anning River and Longmenshan fault zone.It is the high arch dam with the highest seismic fortification standard in the world.In the Luding Ms6.8 earthquake,the dam’s strong earthquake monitoring system recorded a complete seismic waveform,and the maximum peak acceleration along the river reaches 586.63 cm/s^(2).It is the only dam that has undergone the test of near-field strong earthquake among the 200 m high arch dam built in China.According to the macroscopic phenomenon of the dam deformation after the earthquake and the monitoring original data,the deformation of the dam body and the foundation system is analyzed.The results show that the dam is deformed downstream as a whole after the earthquake.The radial displacement increment is between-1.53 mm and 20.04 mm,and the chord extension increment is between 15.27 mm and 23.50 mm.There is an opening and closing process of the transverse joint of the dam during the earthquake.There is a certain residual opening of the low elevation transverse joint,and the increment is between-0.08 mm and 0.46 mm,and the deformation is coordinated as a whole.At the same time,there are some residual dislocations in the abutments on the left and right banks of the dam,the replacement blocks of the dam foundation,the dam and the foundation,which are the main reasons for the large residual deformation of the dam.However,the dam body itself is still in elastic working state,and finally remains stable in the new equilibrium position,indicating that the Dagangshan arch dam has withstood the test of this strong earthquake.The relevant results can provide reference for post-earthquake dam safety assessment,high arch dam seismic design and research.