泸定M_(S)6.8级地震大岗山拱坝横缝及阻尼器工作性态分析

Analysis of working behavior of transverse joints and dampers of Dagangshan arch dam during Luding M_(s)6.8 earthquake

横缝作为高拱坝强度的薄弱部位,在地震作用下的工作性态至关重要。泸定M_(S)6.8级(面波震级)地震中,大岗山拱坝坝顶顺河向峰值加速度PGA达到586.63 cm/s^(2),坝址烈度达Ⅷ度,是唯一经历近场强震考验及设置阻尼器抗震措施的200m级高拱坝。依据震后大坝横缝及阻尼器宏观现象和监测原观数据,对横缝及阻尼器工作性态进行了分析,结果表明地震过程中大坝横缝存在开合过程,震后部分横缝存在残余张开,开度增量在-0.05~0.43mm之间,总体表现为下游侧略大于上游侧,左岸大于右岸,初步分析主要由于横缝高频开合导致灌浆材料部分剥离测缝计无法复位,拱坝仍处于弹性工作状态;拱坝坝顶3组阻尼器在地震前后两端位移增量在0.32~1.06 mm之间,表现为拉伸,其中靠近拱冠梁的16#横缝位移增量最大。结合测缝计监测成果初步分析,阻尼器在强震作用下对降低局部区域横缝开度有一定作用,在主震后的历次余震中阻尼器未见明显动作痕迹。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。

The working behavior of transverse joints during earthquakes is critical to the stability of high arch dams.During the Luding M_(s)6.8 earthquake,the downstream peak ground acceleration(PGA)at the crest of Dagangshan arch dam reaches 586.63 cm/s^(2),and the intensity scale of dam site reaches VIII.The Dagangshan arch dam,which is higher than 200 m,is the only one that has undergone a near-field strong earthquake and adopts dampers as aseismic measures.In this study,the working behavior of transverse joints and dampers after an earthquake is analyzed based on the macroscopic phenomena of dam transverse joints and dampers and the original monitoring data.The results show that the transverse joints undergo a process of opening and closing during the earthquake.Some transverse joints have residual opening after the earthquake,with an opening increment ranging from-0.05 mm to 0.43 mm.The opening increment at the downstream side is slightly larger than that at the upstream side,and the opening increment at the left bank is larger than that at the right bank.This is mainly due to the frequent opening and closing of the transverse joints,which leads to the partial stripping of the grouting material.The joint meter cannot be reset,and the arch dam remains in an elastic working state.The increment in displacement of the three sets of dampers on the top of the arch dam before and after the earthquake ranges from 0.32 mm to 1.06 mm,which represents tensile deformation,and the largest increment in displacement is observed at the transverse joint#16 near the arch crown beam.Combined with the preliminary analysis of the monitoring results of the joint meter,the damper has a certain effect on reducing the opening of the transverse joints in the local area during strong earthquakes,and there is no obvious action trace of the damper in the aftershocks.The research results can provide a reference for the post-earthquake dam safety assessment,as well as seismic design and research of high arch dams.