A Calculation Model for Vibration Effect Induced by Resonance-Free Vibratory Hammer Method

Buildings close to the ground treated by the resonance- free vibratory hammer method are often vulnerable to excessive vibrations. An in situ test of an urban soft site was carried out to investigate the resonance-free vibratory hammer induced vibration effects during construction. Vibration pickups were set at the positions with distances of 15 m, 30 m, 50 m, and 100 m away from the vibration source. On the basis of the results obtained from this investigation, vibration effects of the resonance-free vibratory hammer and safe construction distances were systematically analyzed. The testing results indicate that the vibration in the vertical direction is stronger than that in the other two horizontal directions. The vertical vibration should be the main reference quantity for the foundation treatment by using the resonance-free vibratory hammer method. The predominant frequency of each measuring point in the same direction decreased with an increase of the distance from the vibration source (DFTVS). In terms of the measuring point with a DFTVS of 30 m, the peak values of velocity in all directions were within 5 mm/s, which meet the requirements of the allowable limit of building vibration. According to the in situ testing results, a model for calculating the acceleration exponent of the vibration caused by the resonance-free vibratory hammer technology was established by comprehensively considering the amplitude of acceleration, the attenuation coefficient of THE DFTVS, and the vibration correction factor. Finally, the reliability of the calculation model was verified through the comparison between the calculated results and field vibration experimental results, in which all the correlation coefficients of validation example were above 0.9.

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