Stick-slip dynamics and failure in granular materials
Abstract
This project seeks to understand stick-slip dynamics in dry granular materials by studying carefully chosen systems in two and three dimensions. The PIs will use powerful computational and experimental tools to characterize stick-slip dynamics across the broad range of relevant length and time scales. The goal is to determine how various grain properties and driving mechanisms affect the response of the granular material in regimes where stick-slip behavior is observed. Important questions include: What are the key features of the force networks that cause granular systems to jam, clog, and yield when subjected to external stresses? How do particle shape and particle stiffness affect the larger scale structures associated with stick-slip behavior? How does friction between grains and/or frictional properties of a substrate affect the formation of the force networks associated with stick-slip dynamics, and how does friction affect the dynamics of grain rearrangements during slip events? Are there fundamental differences between 2D and 3D systems? Are the lessons learned from 2D systems transferrable to 3D systems? How does stick-slip dynamics depend on the macroscopic parameters of the driving mechanism, including spring stiffness and loading rate? These questions will be addressed through table-top experiments designed for measuring grain motions and forces on individual particles as well as the stresses applied by the driving mechanism. The 2D experiments employ photoelastic disks and measurement methods developed in the Behringer for visualizing particle flows, rotations, and stresses. 3D experiments will use a laser scanning technique developed in the Behringer lab to obtain comparable data to the 2D experiments. The experiments will be complemented by 2D and 3D discrete element method simulations that enable explorations of a broader range of parameter values and higher resolution analyses of grain scale effects. For the 2D cases, studies will be done on regular polygons with three to ten sides, as well as on disks. Friction coefficients between grains will be varied, and experiments will be performed with the disks resting on a frictional substrate and floating on a fluid layer that eliminates friction with the substrate. For 3D cases, studies will be done on regular polyhedral and non-convex particles as well as spheres. This work will lead to better understandings of industrial and geophysical processes involving granular materials, from sand, pills, and cereals, to seismic faults. The results will provide important information for theories of shear jamming and clogging. The study of shear jamming and its relation to isotropic jamming is rather new, and we may expect to discover phenomena that have not previously been observed or appreciated.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810184
Entities
People
- Joshua E. S. Socolar
Organizations
- Army Contracting Command
- Duke University
- United States Army