Shock-induced liquifaction of a water-saturated rock may occur during the pas-
sage of a large amplitude stress wave, such as that due to an explosive. We
studied this phenomena numerically with the aid of a material model which
incorporates effective stress principles, and experimentally with a gas gun. Our
numerical model is capable of calculating material response for both small and
large deformation and any initial saturation. Phase transitions of the solid
phase and the water phase are also allowed. Fitting the model to dry gas gun
experiments allowed reasonable predictions of nearly saturated experiments.
Liquifaction, the loss of shear strength when pore pressure exceeds the mean
stress, appears to occur during the unloading portion of these experiments.
The pore crushing which occurs, even under fully saturated conditions, leads
to greater attenuation of a stress wave, as well as liquifaction of the rock and a
lengthening of the wave duration, as the wave passes.
The mechanical behavior of many water saturated rocks and soils is known to
follow the law of effective stress. This means that a property, such as modulus
or shear strength, is a function of Pc-aP?,, where Pc is the mean total stress and
Pp is the pore water pressure, and alpha may be a constant or depend on other
conditions. Most modeling of deformation behavior has assumed infinitesimal
strain conditions with the theory by Biot (1941), (Biot and Willis 1957) being
one of the most important examples. More recently, Carroll (1980) and co-
workers (Carroll and Holt 1972, Curran and Carroll 1979, Katsube and Carroll
1987a,b) have been important contributors to this field, with models useful for
finite strain problems and materials with spherical pores. Models useful for large
amplitude wave propagation studies are fewer in number. The large amplitude
problem adds to the complexities of non-linear response of the pore water and
the rock solids, as well as pore crushing, shear and tensile failure.