This paper presents the results of recent ground shock experiments conducted by the U.S. Army Engineer Research and Development Center to further investigate the adequacy of the coupling factor approach to shallow-buried or near-surface detonations. Comparisons between these recent experimental results and results of numerical simulations of the ground shock propagation in soil are presented. It was found that the coupling factor curve currently adopted in design of buried structures does not accurately represent the actual ground shock propagation in soil and that different coupling factor curves are needed for different physical quantities of interest in design. The results presented in this paper also suggest that the coupling factor curves are functions of several parameters in addition to the depth of burial and that numerical simulations can capture reasonably well the ground shock propagation of soil stresses and particle velocities. 1. Introduction The U.S. military has many important deeply buried hardened facilities that must be capable of surviving the effects of conventional weapon attacks, which can result in the detonation of buried explosives in close proximity to the buried structure. These structures are designed to withstand ground shock induced by an explosive event that could occur any distance from the structure, either aboveground or belowground, thereby providing safe harbor for personnel. To achieve a reliable design, accurate methods are needed to predict the ground shock (i.e., radial soil stresses and particle velocities) that propagates from the explosive source to the buried structure. For aboveground detonations, the ground shock induced to the buried structure is minimal, as the vast majority of the explosive energy is transmitted as airblast. As the detonation point moves towards and eventually below the ground surface, the energy transmitted into the ground, and hence the resulting ground shock, increases until a maximum ground shock is produced at a specific depth. The distance from the ground surface to the center of gravity of the detonating charge, considered as positive for below ground explosions, is called depth of burial (DOB). The maximum ground shock is produced at a DOB that is referred to as a “fully coupled” DOB. By definition, the fully coupled DOB is the depth at which burying the bomb any additional amount will not result in additional ground shock transmission. The ground shock for detonations occurring at depths at or below the fully coupled DOB (fully coupled detonations) is quite predictable and can
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