Abstract: The working behavior of transverse joints during earthquakes is critical to the stability of high arch dams. During the Luding Ms6.8 earthquake, the downstream peak ground acceleration (PGA) at the crest of Dagangshan arch dam reaches 586.63 cm/s², 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.

Key words: Luding earthquake, Dagangshan arch dam, transverse joint, damper