Efficient Long-Distance Treatment of Soils with Microbially Induced Calcite Precipitation: from micro to macro: Ariadni Elmaloglou

In pursuit of innovative and more environmentally-friendly geo-engineering solutions for soil stabilization, Microbial-Induced Calcium Carbonate (CaCO3) Precipitation (MICP) has emerged as an alternative to traditional grouting techniques. MICP harnesses microbial activity that facilitates the formation of calcium carbonate precipitations that fill the pores and can improve the mechanical properties of the soil. MICP has been extensively studied in the macro-scale but the need for upscaling in real engineering problems requires further control and prediction on the time and location of precipitates, as well as their size, shape and the thermodynamic stability of polymorphs, in order to achieve an homogeneous MICP treatment over a long distance. The need for answering fundamental questions regarding the micro-scale characteristics of MICP treated soils has led, most recently, to the utilization of microfluidic and optical microscopy tools that enable real-time monitoring of MICP injections under saturated conditions. This PhD study further develops an approach that utilizes the most recent advances in real-time monitoring of MICP to probe how a single MICP treatment adapts to two different microfluidic geometries over a meter-long idealized path, focusing mainly on the chemical efficiency and the effect of induced precipitation on pore-scale morphology. The knowledge acquired from the microfluidic experiments, will be further used to enhance the efficiency and homogeneity in MICP-treated soils in the macro-scale.

Mechanical performance and upscaling of bio-improved soils – Ray Harran

Biogeotechnical engineering has inspired revolutionary solutions that have been the subject of abundant research in the last decade, out of which Microbially Induced Calcite Precipitation (MICP) remains one of most promising. The process aims to bio-cement soils in order to mitigate multiple problems of the underground. In this optic, the work targets the current challenges of MICP treated soils, namely, their mechanical performance and upscaling. Gaps of knowledge in the mechanical response are best tested in the lab, specifically targeting strength, compressibility, and creep. Findings are then be used to filter through the available constitutive models and assess their potential improvement. Concerning the upscaling effort, a state-of-the-art basin was constructed to host large-scale experiments, where MICP can be tested in different soils and hydraulic conditions. With direct contributions to mechanical performance and upscaling of the technique, the work is in line with the global effort to better establish MICP as a sustainable alternative to current soil improvement methods.