Centrifuge Model Testing of Liquefaction Mitigation via Microbially Induced Calcite Precipitation

Abstract

A set of saturated Ottawa sand models were treated with Microbially Induced Calcite Precipitation (MICP) and subjected to repeated shaking events using the 1-m radius centrifuge at the UC Davis Center for Geotechnical Modeling. Centrifuge models were constructed to initial relative densities (DR0) of approximately 38% and treated to light, moderate, and heavy levels of cementation (calcium carbonate contents by mass of approximately 0.8%, 1.4%, and 2.2%, respectively) as indicated by shear wave velocities (light ≈200 m/s, moderate ≈325 m/s, and heavy ≈600 m/s). The cemented centrifuge models are compared to a pair of uncemented saturated Ottawa sand models with initial DR0s of ≈38 and ≈53% and subjected to similar levels of shaking. Cone penetration resistances and shear wave velocities are monitored throughout shaking to investigate (1) the effect of cementation on cone penetration resistance, shear wave velocity, and cyclic resistance to liquefaction triggering and (2) the effect of shaking on cementation degradation. Accelerometers, pore pressure transducers, and a linear potentiometer are used to monitor the effect of cementation on liquefaction triggering and consequences. Cone penetration resistances and shear wave velocities are sensitive to light, moderate, and heavy levels of cementation (increases in penetration resistance from 2 to 5 MPa, 2 to 10 MPa, and 2 to 18 MPa and shear wave velocity from 140 to 200 m/s, 140 to 325 m/s, and 140 to 660 m/s, respectively), and are able to capture the effects of cementation degradation.

Native Bacterial Community Convergence in Augmented and Stimulated Ureolytic MICP Biocementation

“…pasteurii but occasionally with other Firmicutes. − Often such studies repeatedly supplement treated soil specimens with urea and calcium chloride but not with an organic carbon source and, thus, probably do not enrich native ureolytic bacteria to the extent observed here, (refs , , ,, , − , and others). Regularly, however, studies include organics in the augmentation or cementation solutions or prepare the augmentation solution by direct dilution of the rich culture medium, refs , , , , , , , , , − and others. In those cases, the provision of organic compounds could stimulate unintended indigenous microbe growth.…”

“…The produced calcium carbonate largely exists as, or matures to, calcite under most reaction conditions , and forms on soil particle surfaces and contacts, bonding neighboring particles together, thereby acting in bulk to cement the soil. This biocementation alters important engineering behaviors, including increasing shear strength and stiffness, dilatancy, and reducing soil hydraulic conductivity and liquefaction susceptibility. − …”

Review of Strength Improvements of Biocemented Soils

“…The liquefaction of soils that is induced by dynamic loadings could result in the collapse of foundations and superstructures due to the increase in excess PWP (u) and, therefore, a reduction in the effective stress. The MICP technique has proved to be efficient to mitigate liquefaction (Sasaki and Kuwano 2016;Xiao et al 2018;Darby et al 2019;Riveros and Sadrekarimi 2020b;Mousavi and Ghayoomi 2021;Sharma et al 2021b;Sun et al 2021a;Zamani et al 2021;Lee et al 2022). The liquefaction characteristics of biotreated soil with various influencing factors have been studied extensively.…”

NHERI Centrifuge Facility: Large-Scale Centrifuge Modeling in Geotechnical Research

“…The 1-m radius centrifuge, with its smaller models, provides for high throughput of relatively simple tests that enable rapid and efficient exploration of model preparation techniques, in-flight characterization techniques (shear wave velocity V s and cone penetration testing), and degradation of the improved soil in a relatively simple model when subjected to changing static and dynamic loading. In a recent CBBG study (Darby et al, 2019), models were prepared with loose saturated sands having no, light, moderate, and heavy levels of biocementation, and then subjected to multiple shaking events with peak base accelerations of 0.02 to 0.55 g. Arrays of accelerometers and pore pressure transducers were used to compute cyclic stress ratios, shear strains, and excess pore pressure generation. A mini-cone penetrometer was pushed at select times during each test to evaluate the ability of the cone to capture the effects of initial cementation and cementation degradation induced by shaking.…”

“…The inverse-computed CSRs are plotted versus cone penetration and V s values in Figure 13, along with common correlations for estimating liquefaction and non-liquefaction triggering conditions in non-cemented sands (Kayen et al, 2013;Boulanger and Idriss, 2015). Additional details on these tests and their interpretations are provided in Darby et al (2019). The key observations are that the results of these types of tests, starting on the 1-centrifuge and now moving to the 9m centrifuge (with its better resolution on details), provide a unique means for evaluating how industry-standard liquefaction triggering procedures may be adapted to MICP treated sands.…”