Date of Graduation

12-2021

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor

Michelle L. Barry

Committee Member

Wen Zhang

Second Committee Member

Richard Coffman

Keywords

3D printing, Additive Manufacturing, Bio-cementation, MICP, Soil

Abstract

Microbially Induced Calcite Precipitation (MICP) is an emerging soil treatment technique that is proven to increase strength, decrease erosion, reduce liquefaction risk, enhance slope stability, decrease compressibility, decrease swelling potential, and overall create a more competent soil. The benefits and applications of MICP are broad, and this research seeks to broaden them further by developing a single-phase additive manufacturing application with no treatment time delay. This is done by analyzing layering behaviors of five USCS soil classifications (100 % Ottawa sand, sand clay mixtures, and 100% lean clay) which provides insight into process variables such as the solution volume and layer thicknesses for the additive manufactured specimens. Cuboidal specimens were produced using a layering approach where both bacterial and cementation solutions were applied on the surface of every layer using a volume-controlled spray system. The cuboidal specimens were tested in unconfined compression and the results indicated a notable increase in soil strength for clay soils using this treatment method. This application method evades some complexities commonly faced with fine-grained soils. In addition, the potential of utilizing gel spray solutions for higher levels of control when applying solutions in a defined pattern to create mechanically advantageous shapes were considered. The addition of gel to the treatment solutions reduced bleed and allowed for more control. Both potentials show promise but require more examination. All application specifics are highly variant depending on soil type and would need to be calibrated for site-specific projects.

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