Flume study on the effects of microbial induced calcium carbonate precipitation (MICP) on the erosional behaviour of fine sand

Alexandra Clarà Saracho, Stuart K. Haigh*, M. Ehsan Jorat

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

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) via the ureolytic soil bacterium Sporosarcina pasteurii as a method for enhancing the surface erosion resistance of fine sand. Coarse-fine sand specimens were treated with cementation solution concentrations ranging between 0.02-0.1 M, and the erosional behaviour of the fine sand 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 CaCO3 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 amount of CaCO3 precipitated and the concentration of the cementation solution used. To understand this, a systematic study of the CaCO3 crystal sizes and distributions resulting from varying urea-CaCl2 solution concentrations was undertaken through X-ray computed tomography. Fundamentally, the effectiveness of MICP for erosion control was found to be dominated both by the precipitated CaCO3 content and microstructural features, with higher contents and larger crystals yielding lower erodibility values. It was also seen that crystal growth mechanisms could change depending on the urea-CaCl2 solution concentration.
Original languageEnglish
JournalGeotechnique
Early online date14 Jul 2020
DOIs
Publication statusE-pub ahead of print - 14 Jul 2020

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