Journal
GEOTECHNIQUE
Volume 71, Issue 12, Pages 1135-1149Publisher
ICE PUBLISHING
DOI: 10.1680/jgeot.19.P.350
Keywords
erosion; fabric/structure of soils; laboratory tests; reinforced soils; sands; shear strength
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Funding
- University of Cambridge (EPSRC) [EP/L016095/1]
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The study investigated the applicability of microbial induced calcium carbonate precipitation (MICP) for enhancing surface erosion resistance of fine sand. Results showed that untreated specimens eroded primarily in particulate and mass form, while MICP-treated specimens exhibited a block erosion mechanism. Erodibility was found to be influenced by calcium carbonate content and cementation solution concentration.
Tangential flow-induced interface erosion poses a major threat to a wide variety of engineering structures, such as earth-filled embankment dams, and oil- and gas-producing wells. This study explores the applicability of microbial induced calcium carbonate (CaCO3 ) precipitation (MICP) by way of the ureolytic soil bacterium Sporosarcina pasteurii as a method for enhancing the surface erosion resistance of fine sand. Specimens were treated with cementation solution concentrations between 0.02 and 0.1 M, and the erosional behaviour examined in a flume under surface-parallel flow and increasing shear stress. Photographs, cumulative height eroded-time series and erosion rates were obtained as a function of specimen height, MICP treatment formulation and calcium carbonate content. Results showed that while untreated specimens eroded primarily in particulate and mass form, MICP-treated specimens were characterised by a block erosion mechanism. Further, erodibility was found to depend on the calcium carbonate content and the cementation solution concentration. To understand this, a systematic study of the calcium carbonate crystal sizes and distributions was undertaken through X-ray computed tomography. Fundamentally, the effectiveness of MICP for erosion control was found to be dominated both by the precipitated calcium carbonate content and microstructural features, with higher contents and larger crystals yielding lower erodibility values. Additionally, crystal growth mechanisms varied depending on the cementation solution concentration.
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