Crack pattern of indented cohesive granular media.

Abstract

Cohesive granular materials, such as wet sand, retain their shape before yielding under stress, exhibiting a solid-like behavior. As the loading increases, the material typically flows. However, cohesive materials can also develop cracks, similar to those observed in brittle materials. This study investigates the formation of cracks during the indentation of a granular pile. A solid cylindrical indenter is pushed quasistatically into the wet granular medium, causing radial cracks to appear. These cracks resemble mode I cracks observed in brittle elastic solid materials. We characterize the crack pattern through direct observation and three-dimensional X-ray microtomography. Notably, we establish a correlation between the dilation of the material during shearing and the appearance of cracks.