Numerical investigation of effects of water saturation on blast wave propagation in soil mass

The water saturation degree of soils can strongly affect the propagation of blast wave. However, quantitative study of this problem has not been possible due to lacking an appropriate analytical model that is capable of describing the drastically changing behavior of the soil in close-in regions during the blast loading. In this paper, a newly developed three-phase soil model for shock loading is used to study the propagation of blast wave in soils, with particular focus on the influence of the water saturation degree on the stress wave parameters. The multiphase soil model enables the direct inclusion of the energy source in the simulation. Four kinds of fine-grained sand loam with different water saturation degree ranging from 37.5 to 100% are investigated. The numerically predicted camouflet and distribution of damage surrounding the charge show favorable agreement with general experimental observations. The predicted and measured peak wave parameters and their attenuation laws also show a reasonable agreement. The results indicate that a small amount of air in soils could affect significantly the blast wave parameters. For example, with 4% volume of air, the peak pressure in the soil could reduce by 1-2 orders of magnitude as compared to water-saturated soils within a scaled range of 0.5-4.0 (m kg^-1/3), while the peak particle velocity reduces by 2-6 times. The predicted attenuation relations show a noticeable nonlinear trend for soils with relatively high air content (e.g., 15%), and this phenomenon can be attributed to the high nonlinearity of the soil skeleton.