Building Earth materials one grain at a time: Controlling the fluid-driven assembly of complex particulate structures
Abstract
Research problem and objectives: The last decade has seen a unification in our understanding of the physics of idealized particulate systems; frictional, mono-disperse granular flows and suspensions under steady forcing. Particulate Earth materials, however, typically have strong heterogeneity in grain size and composition, are often cohesive, and are subject to time- and space-varying fluid forcing. Accordingly, existing approaches for predicting soil and sediment deformation in nature rely on site-specific calibration of simplistic and phenomenological models. The primary objective of this proposal is to describe, predict and control the stability of particulate Earth materials under a range of environmental fluid-forcing scenarios. In particular, we will focus on improving understanding of creep, aging and yielding of Earth materials. The following objectives support this effort: 1. Build Earth materials in the laboratory to determine the level of irreducible complexity in particulate and fluid composition that gives rise to observed dynamics in natural systems; and 2. Identify emergent meso-scale networks that are linked to mechanical stability of Earth materials, and use this information to coarse-grain the dynamics for mathematical modeling at larger scale. Methods: The following activities outline our technical approach, in support of the objectives above: 1. Novel experiments will tune grain polydispersity, inter-particle attraction and fluid forcing to examine: stiffening and aging of creeping soil; and yielding and the formation of earthflows. Experiments will directly visualize particle-particle and particle-fluid interactions using multi-scale imaging, force-chain illumination, and tomography; and determine resulting bulk rheology using novel fluid shearing methods; and 2. We will use computational tools recently developed at the intersection of machine learning and network science to identify and quantify the structure of particulate networks from experiments, determine which characteristics of these networks exert the strongest influence on ensemble particle dynamics, and use this information to coarse-grain the dynamics for upscaled mathematical modeling. Significance to advancement of scientific knowledge: This work will determine the special mechanical properties of particulate Earth materials that arise from grain polydispersity and transient fluid forcing; and develop novel mathematical tools to predict these behaviors at Army-relevant scales. A primary outcome will be improved understanding of creep and yielding in wet soils and sediments, which will point towards controls that could be implemented to stabilize Earth materials. Impact on DoD capabilities: This work may help to improve assessment of vehicle interactions with wet terrain, and to determine the vulnerability of critical infrastructure that is embedded in landscapes. Further, improved identification of the governing conditions will enable control of unstable Earth Materials by informing design and alteration strategies to achieve desirable behaviors useful to the Army, such as: suppressing soil creep, increasing stiffness, and improving vehicle traction under wet conditions. Finally, this project will train a large cohort of young scientists at the interface of Earth materials and mathematics, ensuring expanded expertise in DoD-relevant fields for the future.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010113
Entities
People
- Douglas J. Jerolmack
Organizations
- Army Contracting Command
- United States Army
- University of Pennsylvania