Analysis On Strong Motion Monitoring And Dynamic Characteristics Of Xinfengjiang Reservoir Dam

Xinfengjiang reservoir dam is the first which has passed the test of an earthquake of magnitude 6 in the world. Nowadays earthquakes occur frequently in the reservoir area. And after the earthquake of magnitude 4.3, a 82 m length penetrating crack has been generated on 108.5m height of dam sections NO.13-17. So it is necessary to analysis aseismic characteristic of dam section NO.8 of Xinfengjiang reservoir dam and the stability analysis of dam sections in which there is a penetrating crack.The paper can be summarized as the following aspects:(1) Influence factors analysis of the dam’s frequency. We identify frequency of Xinfengjiang dam 8# section continuity by using FFD. The influence’s research of generator running to dam vibration effect and influence’s research of water level to modal frequencies of the dam are studied with the data of xinfengjiang reservoir water level、generator running time and frequency. The results show that generator running has a great influence to dam vibration effect and the correlation between water level and frequency of the dam is negative.(2) Analysis of the xinfengjiang reservoir dam 8# dam section.Fem model was established by using ANSYS finite element software. And combining the modal analysis’ s result of the strong vibration array’s real-time monitoring data, the model of dam section NO.8 of is optimized. By static and dynamic analyses we study thedeformation and stress distribution of dam body. The results show that the maximum tensile stress under seismic loading occurs to the dam upstream surface’s mutation.The phenomenon is consistent to the penetrating crack on the mutation of retaining dam upstream surface’s. This should cause a certain attention. Other parts have a certain safety stock under static and earthquake action. Dynamic time history analysis result is bigger than the response spectrum analysis results.(3) Research on penetrating crack and stability of Xinfengjiang reservoir dam.we compared analysis of the dam with penetrating crack to that with no crack by using some small earthquake observation records on the dam body which are up and down of penetrating crack in recent years, analysis of the dam section NO.14’s integrity and stability. Results show that so far, the cracks in the dam are not significantly worse, but integrity is still relatively poor. It is still hidden trouble of the dam stability.