2024 article

Influence of the coefficient of uniformity on bio-cemented sands: a microscale investigation

PROCEEDINGS OF THE 8TH INTERNATIONAL SYMPOSIUM ON DEFORMATION CHARACTERISTICS OF GEOMATERIALS, IS-PORTO 2023, Vol. 544.

By: M. Reed n & B. Montoya n

author keywords: Microbially induced calcium carbonate precipitation; x-ray computed tomography; unconfined compressive strength; coefficient of uniformity
UN Sustainable Development Goal Categories
15. Life on Land (OpenAlex)
Source: Web Of Science
Added: October 21, 2024

Microbially induced carbonate precipitation (MICP) is a bio-mediated ground improvement technique that can increase soil stiffness and produce cohesion within granular material. Most experimental investigations on MICP-treated soils are performed on idealized granular materials. Evaluating a narrow range of particle sizes dismisses the potential influence of soil fabric on MICP treatment efficiency. Therefore, little is known regarding the influence of soil fabric on the level of improvement achievable post-MICP treatment. We investigate the influence of the coefficient of uniformity (C u ) on the level of improvement that can be obtained from MICP treatment. This study couples unconfined compression testing with microscale observations obtained from x-ray computed tomography (CT) of two sand mixtures with different Cu values. A soil column and CT specimen of each sand mixture were prepared and received the same number of MICPinjections. The shear wave velocity (V s ) of the soil columns was monitored to evaluate the increase in soil stiffness over time. After MICP treatment, the bio-cemented columns were subjected to unconfined compressive strength testing. Results indicate that for a similar mass of carbonate, the soil with a larger Cu experienced a greater increase in V s but a lower maximum unconfined compressive strength. Through CT imaging, the soil with a smaller C u was observed to have a more uniform distribution of carbonate within the sand matrix whereas the soil with a larger C u has more sporadic MICP trends. This study elucidates the influence of soil fabric on the level of improvement that can be achieved through MICP treatment and assesses the reliability of x-ray CT scanning of MICP-treated sands with moderate carbonate content.