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| CHARACTERISTICS OF GROUND MOTION INDUCED BY A SHORT DELAY BLASTING IN LOESS FIELD |
| SUN Junjie1，2，QIU Rendong3，XU Shunhua2，WANG Lanmin1，2 |
(1. School of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China；
2. Lanzhou Institute of Seismology，China Earthquake Administration，Lanzhou，Gansu 730000，China；
3. China Academy of Building Research，Beijing 100013，China) |
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Abstract Based on a short delay blasting executed in the typical seismic loess field of Loess Plateau，the time histories characteristics，attenuation laws and frequency spectrum features of ground motion induced by the blasting are investigated. In-situ observation data show that exploding ground motion in loess field has two essential characteristics evidently，i.e. an instantaneous large peak ground acceleration(PGA) and a shorter duration. Analysis results of exploding ground motions reveal that effective duration is the most important factors to influence design effects of a short delay blasting. Independent exploding events in the blasting process have an evident feature that the time histories could be connected each other discretionarily. As a result，the duration of exploding ground motion may be lengthened through this kind of connection work. These connection results of time histories would not influence the spectral characteristics of ground motion induced by the short delay blasting. The new time histories are better in the application of laboratory and field tests to understand the response behaviors of soils and structures. The spectral response of blasting ground motion tends to attenuate with the increase of distance between the center of exploding field and observation points，especially for the high frequency ground motion，which has a greater reduction distinctly. The H/V values of frequency spectrum，meanwhile，become greater with the observational distances increase gradually. This phenomenon figures the variation features between horizontal component and vertical component of exploding ground motion. As the exploding energy accumulates，lower frequency energy of ground motion associates with the blasting increases gradually；and the frequency spectrum features of the ground shock approach an actual seismic oscillation by degrees.
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Received: 28 May 2010
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2011, Vol. 30 
