Soil Reactions in Saturated Sand Caused by Impulsive Loads

Abstract

It is demonstrated that reactions for impulsive loads in saturated sand soil are speed dependent and can be far higher than the reactions for the corresponding slow loads. The reason is that soils rupture and pore water flow interacts, both for contractive sand and for dilatant sand and create additional pore water pressures and additional effective stresses. The traditional geotechnical methods, the extreme method, and the equilibrium methods have been extended to also include the interaction between ruptures and pore water flow. It is shown that zone ruptures generally will be dilatant except possibly for the loosest layering. This means that the pore water will be sucked into the rupture zone when it develops. This may not be the case with line ruptures, where the soil may be mainly contractive and squeeze out pore water during the development. Analytical methods have been developed and compared with laboratory results for falling cones penetrating into saturated sand. Both tests and analysis compared well and showed an increase from 2 to 70 times in average resistance compared with dry sand depending on the relative density of the sand and the ratio between speed of penetration and permeability.