Experimental study on seismic coupling effects of underground explosions in different materials

Underground explosion experiments with the explosion equivalent of 100 kg TNT were performed in different geological mediums, such as loess, sand-gravel composite and granite. And the corresponding surface ground motions induced by underground explosions were observed by a series of seismometers. By using these observed data, the source parameters were obtained, as well as the seismic coupling efficiency represented by the steady value of reduced velocity potential at low frequencies. Experimental results display that for the underground explosions with the same scaled depth of burial and same explosion equivalent, the seismic coupling efficiency was strongly dependant on the source medium property in such a way that the medium strength plays the most significant roles in determining the seismic coupling effect and then the porosity and the water saturation. And based on the experimental data, the feasibility of the empirical formula proposed by M. D. Denny, et al was analyzed in estimating the seismic coupling effect of underground explosions with the explosion equivalent of 100 kg TNT.