Enzymatic-Induced Calcite Precipitation (EICP) Method for Improving Hydraulic Erosion Resistance of Surface Sand Layer: A Laboratory Investigation

Seyed Mohammad Ali Zomorodian (), Sodabeh Nikbakht, Hamideh Ghaffari and Brendan C. O’Kelly ()
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Seyed Mohammad Ali Zomorodian: Department of Water Engineering, Shiraz University, Shiraz 7144165186, Iran
Sodabeh Nikbakht: Department of Water Engineering, Shiraz University, Shiraz 7144165186, Iran
Hamideh Ghaffari: Department of Water Engineering, Shiraz University, Shiraz 7144165186, Iran
Brendan C. O’Kelly: Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, D02 PN40 Dublin, Ireland

Sustainability, 2023, vol. 15, issue 6, 1-17

Abstract: As a bio-inspired calcite precipitation method, bio-grouting via enzymatic-induced calcite precipitation (EICP) uses free urease enzyme to catalyze the urea hydrolysis reaction. This soil stabilization approach is relatively new and insufficiently investigated, especially for applications involving surface layer stabilization of sandy soil deposits for increasing hydraulic erosion resistance. This paper presents a laboratory investigation on the surface erosion resistance improvements for compacted medium-gradation quartz sand specimens mediated using 10 different EICP treatment protocols. They involved single- and two-cycle injections of the urease enzyme (activity of 2400 U/L) and 0.5, 0.75, or 1.0-M urea–CaCl 2 cementation solution reagents. The urease enzyme was extracted from watermelon seeds. Erosion rates were determined for various hydraulic shear stresses applied using the erosion function apparatus. The spatial distribution and morphology of precipitated calcite within the pore-void spaces of the crustal sand layer were investigated with a scanning electron microscope. Compared to untreated sand, all 10 investigated EICP treatment protocols produced substantially improved erosion resistance, especially for the higher cementation solution concentration (1.0 M). Of these 10 EICP protocols, a single cycle of enzyme–1.0-M-cementation solutions injections was identified as the more pragmatic option for achieving near-optimum erosion resistance improvements. Highest and lowest amounts (18.8 and 5.0 wt%) of precipitated calcite corresponded to the best and worst performing EICP-treated specimens, although the calcite’s spatial distribution in treated specimens is another important factor.

Keywords: bio-cementation; bio-grouting; erosion function apparatus; hydraulic erosion; scouring; soil stabilization (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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