Experimental observation for dynamic characteristics of 'Shimajiri Mahji' and its evaluation using computational simulation

摘要

We perform herein a direct observation of shockwave propagation using a high-speed camera and estimate properties, such as acoustic velocity and Hugoniot parameter, using the impedance matching scheme to reveal the dynamic characteristics of Okinawa's unique soil "Shimajiri Mahji." A computational simulation corresponding to the experimental setup is then conducted. A comparison of the numerical and experimental results demonstrates their fairly good agreement, which suggests that the experimentally estimated dynamic characteristics of "Shimajiri Mahji" are valid. In addition, a computational simulation based on the smoothed particle hydrodynamics is also modeled and performed to elucidate the fragment behavior when the unexploded bomb explosive is at the soil surface. From a series of computational results, we have confirmed and clarified that the fragment behavior is significantly dependent on the amount of explosive charge and soil characteristics.