Microscale analysis of fractured rock sealed with microbially induced CaCO3 precipitation : influence on hydraulic and mechanical performance

Tobler, Dominique J. and Minto, James M. and El Mountassir, Grainne and Lunn, Rebecca J. and Phoenix, Vernon R. (2018) Microscale analysis of fractured rock sealed with microbially induced CaCO3 precipitation : influence on hydraulic and mechanical performance. Water Resources Research, 54 (10). pp. 8295-8308. ISSN 1944-7973

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    Abstract

    Microbially induced CaCO3 precipitation (MICP) has shown great potential to reduce permeability in intact rocks as a means to seal fluid pathways in subsurface ground, for example to secure waste storage repositories. However, much less is known about how to apply MICP to seal fractured rock. Furthermore, there is limited information on the hydraulic and mechanical properties of MICP filled fractures, which are essential criteria to assess seal performance. Here, MICP injection strategies were tested on sandstone cores, aimed at obtaining a homogeneous porosity fill that reduced permeability by 3 orders of magnitude. The injection strategy resulting in the most homogenous calcite distribution was then applied to fractured granite cores, to yield transmissivity reduction of up to 4 orders of magnitude. Microscale analysis of these sealed granite cores using X‐ray computed tomography and electron microscopy showed that > 67% of the fracture aperture was filled with calcite, with crystals growing from both fracture planes, and bridging the fracture aperture in several places. Shear strength tests performed on these cores showed that the peak shear strength correlated well with the percentage of the fracture area where calcite bridged the aperture. Notably, brittle failure occurred within the MICP grout, showing that the calcite crystals were strongly attached to the granite surface. If MICP fracture sealing strategies can be designed such that the majority of CaCO3 crystals bridge across the fracture aperture, then MICP has the potential to provide significant mechanical stability to the rock mass as well as forming a hydraulic barrier.

    Author(s):Tobler, Dominique J., Minto, James M. ORCID logoORCID: https://orcid.org/0000-0002-9414-4157, El Mountassir, Grainne ORCID logoORCID: https://orcid.org/0000-0003-4213-8182, Lunn, Rebecca J. ORCID logoORCID: https://orcid.org/0000-0002-4258-9349 and Phoenix, Vernon R. ORCID logoORCID: https://orcid.org/0000-0002-8682-5200
    Item type:Article
    ID code:65591
    Keywords:ureolysis, shear strength, water protection, fracture grouting, calcite growth, X-ray computed tomography, Hydrology. Water, Environmental engineering, Water Science and Technology, Geotechnical Engineering and Engineering Geology
    Subjects:Geography. Anthropology. Recreation > Physical geography > Hydrology. Water
    Technology > Engineering (General). Civil engineering (General) > Environmental engineering
    Department:Faculty of Engineering > Civil and Environmental Engineering
    Depositing user: Pure Administrator
    Date deposited:01 Oct 2018 15:38
    Last modified:21 Aug 2019 15:59
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/65591
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