Seismic and Resistivity Measurements for Real-Time Monitoring of Bio-Mediated Soil Improvement
Abstract
A variety of biogeochemical processes, from inorganic mineral precipitation, to bio-film formation, to bio-gas generation, are being investigated as alternative methods to improve soil properties. Every process applied in a geotechnical or geoenvironmental application requires the ability to monitor the progression of treatment, preferably in real-time. While monitoring of the biogeochemical processes is necessary to properly apply and manage the treatment process, ultimately verification that the treatment is improving the desired engineering soil properties as desired is necessary. Since direct measurements of soil properties (e.g. strength tests) during treatment are infeasible, the use of indirect non-destructive measurements during treatment is desirable. Development of these real-time, non-destructive measurements would increase the "certainty of execution" of bio-treatment methods. Seismic velocity and resistivity measurements were examined to assess their ability to monitor the extent and spatial distribution of microbially induced calcite precipitation (MICP) in sands. The relative merits of shear and compression seismic measurements as well as resistivity (the real component) are first reviewed conceptually. Results from a series of experimental tests on silica sand are then presented. Shear wave velocity (S-wave) test results are used to develop a generalized correlation to the precipitated calcite mass (Figure 1), which in turn enables prediction of changes in void ratio (porosity), density, and shear modulus during treatment. Compression wave velocity (P-wave) measurements are determined under different saturation conditions and used in combination with S-wave measurements to observe how the Poisson's ratio evolved during treatment (Figure 2). The applicability of the real component of resistivity measurements for monitoring the MICP treatment process is also examined. Finally, the implications of these results for real-time monitoring during future field-scale applications discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B23D..02D
- Keywords:
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- 0416 BIOGEOSCIENCES / Biogeophysics;
- 0418 BIOGEOSCIENCES / Bioremediation;
- 0419 BIOGEOSCIENCES / Biomineralization