Surface-covering water significantly amplifies the explosion impulse of shallow buried explosives

While the moisture content of soil affects significantly the blast impulse of shallow buried explosives, the role of surface-covering water (SCW) on soil in such blast impulse remains elusive. A combined experimental and numerical study has been carried out to characterize the effect of SCW on transferred impulse and loading magnitude of shallow buried explosives. Firstly, blast tests of shallow buried explosives were conducted, with and without the SCW, to quantitatively assess the blast loading impulse. Subsequently, finite element (FE) simulations were performed and validated against experimental measurement, with good agreement achieved. The validated FE model was then employed to predict the dynamic response of a fully-clamped metallic circular target, subjected to the explosive impact of shallow buried explosives with SCW, and explore the corresponding physical mechanisms. It was demonstrated that shallow buried explosives in saturated soil generate a greater impulse transferred towards the target relative to those in dry soil. The deformation displacement of the target plate is doubled. Increasing the height of SCW results in enhanced center peak deflection of the loaded target, accompanied by subsequent fall, due to the variation of deformation pattern of the loaded target from concentrated load to uniform load. Meanwhile, the presence of SCW increases the blast impulse transferred towards the target by three times. In addition, there exists a threshold value of the burial depth that maximizes the impact impulse. This threshold exhibits a strong sensitivity to SCW height, decreasing with increasing SCW height. An empirical formula for predicting threshold has been provided. Similar conclusions can be drawn for different explosive masses. The results provide technical guidance on blast loading intensity and its spatial distribution considering shallow buried explosives in coast-land battlefields, which can ultimately contribute to better protective designs.