Sand particles crush when the granular matrix is subjected to high stresses. Although particle crushing mechanics are fairly well understood, there is limited understanding of the reciprocity between seepage and crushing. At post-yield stresses, the permeability evolution is controlled by pore size reductions and increased specific surface. Conversely, optimal conditions for fragment migration are expected at pre-yield and early post-yield stresses, where the pore throats are relatively large and the fragments produced by attrition can be sufficiently small to migrate through the porous network. In this case, the loss of solids results in an internally-unstable matrix. This research program aims to identify and examine emergent micro-mechanisms and the ensuing macro-level response of sands subjected to (1) seepage post-crushing and (2) seepage and crushing simultaneously.
Unique laboratory devices, custom particulate mixtures, transparent soil technology, DEM simulations, SEM microscopy, and high-resolution particle size analyses will be used to (1) evaluate the influence of mineral composition heterogeneity on crushing/flow response and (2) determine dimensionless ratio thresholds for fragment generation, migration, and internal instability.
The intellectual merit of this research is an improved understanding of the mechanisms by which particle crushing and seepage induce variations in permeability, fabric, and gradation. These parameters are important in establishing drained -to- undrained transitions in applications where sands are subjected to stresses that can lead to the production of migratory fragments, such as in water- and oil- producing formations and in saturated sediments subjected to dynamic loads. The goals of this research translate to broader impacts in petroleum and hydrate geomechanics, engineered filters, powder and mineral processing, physics of granular matter, and agricultural engineering.
The educational component is the development of didactic web-based and demonstrative tools that will be used in summer courses pertaining to Project Lead the Way. This nationally established program is aimed to increase the number and quality of engineering graduates via pre-college courses developed for instructing middle and high school teachers in engineering education.
