Microbially induced calcite precipitation is bio-mediated calcite precipitation process that can improve the geotechnical properties of granular soils. Bio-cementation offers an environmentally conscious alternative to more traditional ground improvement methods by utilizing natural microbial activity to induce calcite precipitation on soil particle surfaces and at particle contacts. Previous research studies have demonstrated the ability of bio-cementation to increase soil shear strength, initial shear stiffness, liquefaction resistance, and reduce hydraulic conductivity and porosity; however, few researchers have examined the shearing behavior of bio-cemented sands at the particle scale. In this study, four poorly-graded sand specimens were treated to different levels of bio-cementation and subjected to drained triaxial compression. During shearing, the internal structure of soil specimens was examined using X-ray computed tomography and various digital image correlation techniques. Results demonstrate that various levels of bio-cementation can increase peak shear strength by 47% to 1487%, reduce internal deformations required to mobilize peak strength, and change the onset of shear banding from a gradual and widespread development to a more abrupt and narrow feature after failure.
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