Spectral induced polarization study on enzyme induced carbonate precipitations: influences of size and content on stiffn
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RESEARCH PAPER
Spectral induced polarization study on enzyme induced carbonate precipitations: influences of size and content on stiffness of a fine sand Bate Bate1 • Junnan Cao2
•
Chi Zhang3 • Na Hao1
Received: 9 April 2020 / Accepted: 12 August 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Heterogeneity in either chemically or microbiologically induced carbonate-based ground improvement methods is a major obstacle in engineering application. Spectral induced polarization (SIP), an innovative and nondestructive method, which has demonstrated promise in monitoring microbial activity, was used in this study to monitor enzyme induced carbonate precipitation (EICP). The complex conductivities, together with the shear wave velocities (Vs), of an EICP modified sand were monitored using a self-developed spectral induced polarization–bender element column. The mean precipitate size was calculated by relaxation time (s) and the Schwarz equation. The precipitate contents were calculated by cumulative gamma distribution function on the global polarization magnitude (mn) with R2 = 0.989. The stiffness of the enhanced geomaterial, in terms of Vs, correlates to mn with a cumulative lognormal distribution function with R2 = 0.967. Contact cementation was postulated as the dominant association pattern. The possible mechanism for this may be the formation of eddies and the nucleation of CaCO3 crystals during precipitation. The results suggest that SIP can be used as an effective nondestructive monitoring tool to assess the stiffness of geomaterials. Keywords EICP Precipitated particle size Shear wave velocity Solid content Spectral induced polarization Stiffness
1 Introduction
& Junnan Cao [email protected] Bate Bate [email protected] Chi Zhang [email protected] Na Hao [email protected] 1
Institute of Geotechnical Engineering, College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China
2
Department of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology, 1401 North Pine Street, Rolla, MO 65409, USA
3
Department of Geology, The University of Kansas, Lawrence, KS 66045, USA
The use of biological systems in engineering applications has drawn increasing attention over the past decade [20, 21, 28]. For example, microbial induced carbonate precipitation (MICP) has been extensively investigated [20, 21, 44, 65, 67, 75]. It holds promising potential applications in slope stability [54], erosion control [32, 45], bearing capacity of shallow foundations [46], dust control [26, 28, 45, 63], stabilization of expansive clays [31] and liquefaction mitigation [31, 48]. MICP is most suitable for the coarse-grained soils with pore sizes larger than the size of the bacteria in question. Challenges that microbial activity induced soil improvement methods face include heterogeneity during deployment, bioclogging (pore space clogging), and the generation of enviro
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