Date of Award
Master of Science
Geological and Atmospheric Sciences
Jacqueline E Reber
Two-phase systems, in which one phase is solid and the other fluid, are widespread in nature. Examples of such systems include reservoir rocks holding vital fluids like water or petroleum; slurries of partially crystallized magmas; the semi-brittle middle crust where, at the same pressure and temperature conditions, some minerals fracture in a brittle manner while others flow in a ductile manner; and fluids migrating along faults filled with fault gouge. Previous studies of two-phase systems have shown that they deform in a complex manner, where the weak phase plays an important role on deformation localization and dynamics. Here, I study the influence of a weak phase on stress distribution in a granular medium. To this end, in my experiments I deform a two-phase material in a simple shear apparatus under constant strain rate. I use photoelastic polyurethane discs as the granular or strong phase and a linear-viscous silicone as the weak phase. The photoelastic property of the discs allows for direct observation and measurement of force distributed throughout the system. I compare the two-phase experiments to granular experiments without the silicone. In the granular experiments I observe force chains, connected sequences of highly stressed discs, forming in a framework pattern oriented parallel to the principal stress direction. With the addition of the fluid, force initially localizes along the shear plane imposed by the experimental apparatus. The results show that the fluid phase can support force locally over an extended period of time. In contrast to the granular experiment, force chains can terminate within the experiment. The addition of the weak phase has a strong impact on the force distribution and the force chain orientation. In the two-phase system, the force chains form parallel to the shear plane and only rotate to the principal stress direction with an increase in strain. The experiments presented here quantify the impact of the weak phase in a granular system during deformation.
Christopher R. Ladd
Ladd, Christopher R., "An experimental analysis of force distribution in a two-phase system" (2020). Graduate Theses and Dissertations. 17912.