Study On The Blasting Vibration Response And Vibration Control Of Ancient Buildings During Rail Tunnel Construction

In recent years, the development of the light rail has effectively reduced the traffic pressure brought in by the fast urbanization, while the effects of the blasting vibration in the course of light rail construction on the buildings around is also attracting more and more attentions. Although much research has been conducted by scholars at home and abroad about the blasting seismic effects on buildings and its control, while seldom involves in structure vibration characteristics of ancient buildings under the effect of blasting seismic and vibration control, which are special structures or different types. Therefore, it has very important theoretic research value and engineering guidance significance to research structures vibration characteristics of the ancient buildings under the effect of blasting vibration and vibration control.Relying on Asoka Hill tunnel blasting vibration security monitoring project, the research on structure vibration characteristics of Asoka Temple under the light rail blasting vibration and the earthquake effect control has been completed in the thesis through theoretic analysis and field test, and such research conclusions and results have been acquired as follows:1. The rule of light rail tunnel blasting seismic wave propagation and attenuation in Ningpo area has been acquired after engineering blasting vibration observation test and analysis, and through the analysis on the observation test results, it has got the empirical formula on the peak particle vibration velocity with explosive dosage and distance, at the point closer to ground and farther from railroad bed along the vertical directions of building foundation, horizontal level radial and tangential.2. These conclusions have been obtained by analyzing blasting seismic wave time-frequency characteristics and distance comparison, which it is shown that the peak vibration velocity changes faster with explosive dose and distance in horizontal direction than the vertical. And compared with the earlier attenuation relation between the peak particle vibration velocity and explosive dose, there is obviously an uplifting attenuation index a, which shows that blasting vibration attenuates faster at a farther distance. And the main vibration frequency mainly ranges between 10~70Hz with the highest frequency ranging 10~20Hz.3. The finite element numerical analysis model has been established and through the analysis on dynamic response, structural vibration mode theory and data of the three ancient buildings which are the Brick Towel, Mountain Gate and King Hall, the natural frequency of each order has been got and the result shows that the natural frequency of the first order matches, while the second and the third order differ, and meanwhile, the peak vibration velocity response value of the three ancient buildings are all bigger than the allowable values for national important cultural relic buildings under industrial vibration source. That suggests that while considering the effects of the continuous vibration, the blasting earthquake is likely to impose some fatigue fracture on ancient buildings. Therefore, it is best to use a small value as the criterion of particle vibration velocity, considering blasting earthquake accumulating effects.4. The analysis results of the two double-hipped roof structure dynamic response and vibration types of the three ancient buildings, which are the Brick Towel, Mountain Gate and King Hall, suggest that the natural frequency of Brick Towel and King Hall is generally ranged 1~10Hz, and there is a rising tendency of the second and third level natural frequency, the possible overlapping of the main frequency of the blasting vibration with the natural frequency of the ancient structure is bound to result in structure resonance and enlarge dynamic response. That reflects that blasting vibration security judgment shall take comprehensive consideration of the scientific rationality of the vibration velocity and the main frequency.5. Based on the actual situations of the field, light rail tunnel blasting seismic control technology and method have been raised, which are the selection of the type of explosive and blasting approach, using reasonably the geographic conditions, controlling the security distance, and considering the differentiation of different buildings.