Text

theses

Urbanization growth rate is increasing exponentially and with that comes challenging issues in urban development and environment sustainability. Generally, any development processes disturb the environment, and soil stabilization as one of the first steps in infrastructure building is no exception. However, in the past few decades, methods have been sought to reduce the possible harmful impact of soil stabilization processes on the environment. One promising method is microbial induced carbonate precipitation (MICP); in which, ubiquitous soil microorganisms stabilize the loose soil in natural and minimally harmful ways. Although MICP is continuously being studied in multi-disciplinary research, there are still ambiguities in understanding its subsurface processes. This is commonly due to lack of proper monitoring tools capable of providing coherent micro and macro scale information about MICP in subsurface. Geophysical methods are handy tools capable of providing images of the subsurface with high spatiotemporal resolution; while, being cost efficient, non-disruptive and viable for long-term monitoring applications.
This thesis is investigating the efficiency of induced polarization (IP) in monitoring MICP processes and comparing it to direct monitoring methods as well as other geophysical methods. IP is known as a sensitive method to interfacial changes within fluid-grain boundaries in porous media; hence, it is a great measure to study MICP where most changes happen in this boundary (e.g., precipitation of calcite). In this three-phase study, firstly, it is shown that spectral IP (SIP) is capable of tracking changes due to calcite precipitation (the main byproduct of MICP) in the porous media, induced by chemical reactions in a laboratory scale experiment. Compared to resistivity and shear-wave velocity, SIP provided additional information with calcite precipitation pattern. Secondly, in a field scale study, time-domain IP is compared to direct monitoring approaches (e.g., chemical analysis) and showed spatial and temporal extents of MICP in the subsurface; while, direct methods failed to provide such information. And finally, in a more in depth study, it is shown that SIP can reveal frequency dependency of MICP in both laboratory and field scale settings. The additional information provided by IP compared to other methods indicate that IP is the prime candidate for monitoring MICP processes.

ETD_10325

Ph.D.

Includes bibliographical references

doi:10.7282/t3-scpk-bd54

ETD doctoral

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