Experimental Study on the Seismic Efficiency of Rock Blasting and Its Influencing Factors

The seismic efficiency of a blast is the percentage of seismic energy in the total energy delivered by the explosives. It is a key indicator of the blast effects in civil engineering and seismic exploration. A method to determine seismic efficiency has been proposed based on the assumption of spherical wave radiation in an indefinite elastic medium and has been used in a series of blast tests performed at the construction site of a nuclear power plant. Analysis of the influencing factors of seismic efficiency shows that seismic efficiency increases with an increasing explosive charge and stemming length of the blastholes, while it decreases with an increasing decoupling coefficient. Generally, seismic efficiency is markedly lower in bench blasts than in paddock blasts due to free surface effects. Under any circumstances, the seismic energy only accounts for a few percent of the explosive energy. A comparison with theoretical solutions proves that the errors in the present method are low and acceptable in engineering. Therefore, some practical measures have been proposed to improve or lower the seismic efficiency according to the specific requirements of the blast operations.