Abstract:

Field test of vibration velocity was carried out during the excavation of cable shaft in Xiluodu Hydropower Station. The attenuation formulas of seismic wave propagation were obtained through regression analysis of the test data with Sadaovsky empirical formula. Vibration velocity of measuring points in range of 18.2-24.5 meters away from the bottom of shaft in height were predicted with the attenuation formula. Comparison between the data of in-situ test and prediction showed an elevation amplification effect in the propagation of seismic wave and the magnification coefficient of horizontal velocity was about 1.49-2.24 while the vertical was about 1.78-2.73. Sadaovsky empirical formulas were corrected by taking the amplification effect into account and corresponding attenuation formulas were obtained. The corrected formulas presented significant linear relationship and to be references to similar projects. Dynamic finite element method was used to simulate the responses of the shaft under the load of blasting. It is indicated that the trend of the numerical simulation results is fit with that of the field testing data when the height from the bottom of the shaft to the measuring points were not so large. The vibration velocity attenuated rapidly when the distance from the measuring points to the bottom of the shaft were within 0-15 meters and more than 60% of overall vibration velocity attenuated in this range. Less than 10% of the overall vibration velocity attenuated when the distance was over 30 meters. Strength failure criterion of rock-concrete was adopted to check the stability of the shaft under blasting load and references for the safety of the following construction were provided.

Key words: cable shaft, blasting vibration, regression analysis, elevation amplification effect, numerical simulation