ABSTRACT

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.

INTRODUCTION

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.

This content is only available via PDF.
You can access this article if you purchase or spend a download.