ERI: Experimental Study of Grain-scale Mechanics in Bonded Sands

This Engineering Research Initiation (ERI) award supports research to investigate the micromechanical behavior of sand grain pairs bonded with different cementing agents. Bonded granular materials, where particles are bound by cementing agents, are widely present in applications such as infrastructure rehabilitation, ground improvement, liquefaction resistance, and erosion control. Conventional geotechnical laboratory tests often exhibit uncertainties in the loading and strength responses of bonded soils due to variations in cementation type and content. They also lack the resolution needed to capture the underlying micromechanical responses that govern material behavior. This project seeks to address these gaps through systematic laboratory experiments and microscopic observations at the scale of individual grains, focusing on the effects of cement type, particle characteristics, and loading conditions on influencing bond strength and failure mechanisms. Improved understanding of grain-scale mechanics in bonded soils will advance fundamental knowledge, support the design of effective soil stabilization strategies, and contribute to the resilience of the nation’s civil infrastructure. The research also looks to support education and outreach through curriculum development, demonstrations of cementation-based soil treatment, and outreach activities through Michigan Tech’s Summer Youth Programs. Data produced from this project will be archived and made publicly accessible through the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org).

The effectiveness and durability of bonding, as well as the macroscale mechanical behavior of bonded granular materials, are primarily governed by inter-particle cementation. This research seeks to advance understanding of the fundamental grain-scale loading response through systematic experiments on bonded grain pairs. A custom-built inter-particle loading apparatus will be used to assess the loading behavior and bond strength of both natural and artificial sands bonded with a range of cementing agents, including Portland cement, gypsum, and biologically induced calcium carbonate precipitation. This work will specifically (1) investigate the effects of particle size and morphology on grain-scale tensile and shear strength of the bond between particles, (2) compare the role of different cementitious agents on bond strength and deformation response for individual grain pairs, and (3) analyze inter-particle friction and stiffness degradation at the interface of bonded grains following bond failure. This will facilitate the development of a crucial dataset aimed at enhancing the fundamental understanding of the contact mechanics of bonded sands and addressing uncertainties related to their macroscale responses. This work will also lay the groundwork for developing evidence-based numerical modeling strategies, specifically for use in discrete element method (DEM) based simulations of bonded granular materials.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Award Number: 2501898
Principal Investigator: Sai Sandeep Chitta
Funds Obligated: $199,638
State: MI