Innovative methods of ground improvement for railway embankment peat fens foundation soil

Safdar, Muhammad Umair; Mavroulidou, Maria; Gunn, Michael; Garelick, Jonathan; Payne, Ian; Purchase, Diane

doi:10.1680/jgeot.19.sip.030

Cited by 15 publications

(22 citation statements)

References 40 publications

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“…During the treatment by 2 mol/L concentrated urea (cases 15), the hydrophobic interactions in protein molecules were possibly disrupted, resulting in reduced functionality of bacteria. Perhaps, as Safdar et al (2021) indicated, higher calcium chloride concentrations (e.g., 2 mol/L) also might inhibit the urea hydrolysis. Here, the finding demonstrates that for an effective stabilization of the peat soil, the concentration of MICP resources needs to be determined appropriately.…”

Section: Effect Of Binder Dosage On Unconfined Compressive Strength Of the Peatmentioning

confidence: 96%

“…Particularly, the abovementioned challenge is more pronounced for amorphous peat, which has lower open pore structures and hydraulic conductivity compared to those of fibrous peat. Following the proposal by Keykha et al (2012), Safdar et al (2021) involved electrokinetic injection to overcome the limitations related to the rate of transport in peat soils. In due course, Chen et al (2021) proposed and demonstrated a dry mixing approach for effectively treating the peat.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Scallop Powder Addition on MICP Treatment of Amorphous Peat

Gowthaman

Chen

Nakashima

et al. 2021

Front. Environ. Sci.

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Peat is one of the most challenging and problematic soils in the fields of geotechnical and environmental engineering. The most critical problems related to peat soils are extremely low strength and high compressibility, resulting in poor inhabitancy and infrastructural developments in their vicinity. Thus far, peat soils were stabilized using Portland cement; however, the production of Portland cement causes significant emission of greenhouse gases, which is not environmentally desirable. Microbial-induced carbonate precipitation (MICP) is an innovative technique for improving the mechanical properties of soil through potentially environmentally friendly processes. This article presents a laboratory study carried out with the aim of investigating the viability and effect of scallop shell powder (SSP) on enhancing the mechanical properties of the MICP-treated amorphous peat. The hypothesis was that the distribution of SSP (as-derived calcite particles) would (i) provide more nucleation sites to precipitates and (ii) increase the connectivity of MICP bridges to facilitate mineral skeleton to amorphous peat, accompanied by an increase in its compressive strength. Specimens were treated at varying combinations of SSP and MICP reagents, and the improvement was comprehensively assessed through a series of unconfined compression tests and supported by microscale and chemical analyses such as scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction analysis. The outcomes showed that incorporating SSP in MICP treatment would be a promising approach to treat amorphous peat soils. The proposed approach could improve the unconfined compressive strength by over 200% after a 7-day curing period, while the conventional MICP could not exhibit any significant improvements.

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Section: Effect Of Binder Dosage On Unconfined Compressive Strength Of the Peatmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Effect of Scallop Powder Addition on MICP Treatment of Amorphous Peat

Gowthaman

Chen

Nakashima

et al. 2021

Front. Environ. Sci.

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“…Based on its ash content by dry weight, which was < 25%, the soil is equally classified as peat (basic sapric peat) according to ASTM D4427-92 [33]. Further details on the sample characterisation are presented in Safdar et al [30].…”

Section: Soil Sample Characterisationmentioning

confidence: 99%

“…Recent work by the authors [29,30] has proven the feasibility of biocementing peat fens soil of the Nordelph Peat formation, taken from a site of the East Anglia railway network route. This is a soft, unstable organic foundation soil of ca.…”

Section: Introductionmentioning

confidence: 99%

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Towards the Development of Sustainable Ground Improvement Techniques—Biocementation Study of an Organic Soil

et al. 2021

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Ongoing research effort is dedicated to the development of innovative, superior and cost-effective ground improvement techniques to mitigate natural and man-made hazards while minimising waste and other environmental impacts. In this context, the nature-based process of biocementation of soils has been proposed as a potentially more sustainable technique than conventional chemical ground improvement practices. This paper focuses on the biocementation of an organic soil of the UK railway network. Having recently proven the feasibility of biocementing this soil using indigenous ureolytic bacteria, in this paper, the authors perform a parametric study to identify treatments successful in increasing the strength of the soil. Selected treatments are then applied to the soil to assess its volume change during consolidation, secondary compression and shrinkage upon drying. The results show that, depending on the treatments used, biocementation has increased the unconfined compressive strength by up to 81% compared to that of the control samples. For selected treatments and the range of water contents tested (55–33%), shrinkage upon drying reduced by 16%, while the volumetric strains of the soil upon 1-D compression reduced by 32–47%. This was reflected in the values of the coefficient of volume compressibility and the coefficient of secondary compression (the latter either reduced by up to an order of magnitude or secondary compression was not observed altogether in the testing period). Overall, the results proved that biocementation improved considerably the mechanical properties of the organic soil, which gives promise for addressing the settlement problems of this soil.

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Influence of humic acid on microbial induced carbonate precipitation for organic soil improvement

Chen

Gowthaman

Nakashima

et al. 2022

Environ Sci Pollut Res

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Microbial Induced Carbonate Precipitation (MICP) is one of the most commonly researched topics on biocementation, which achieves cementation of soil particles by carbonate from urea hydrolysis catalyzed by microbial urease. Although most MICP studies are limited to stabilizing sandy soils, more researchers are now turning their interest to other weak soils, particularly organic soils. To stabilize organic soils, the influence of humic substances should be investigated since it has been reported to inhibit urease activity and disrupt the formation of calcium carbonate. This study investigates the effect of humic acid (HA), one fraction of humic substances, on MICP. For this purpose, the effects of HA content on CaCO3 precipitation using three strains and on CaCO3 morphology were examined. The results showed that native species in organic soils were less adversely affected by HA addition than the exogenous one. Another interesting finding is that bacteria seem to have strategies to cope with harsh conditions with HA. Observation of CaCO3 morphology revealed that the crystallization process was hindered by HA to some extent, producing lots of fine amorphous precipitates and large aggregated CaCO3. Overall, this study could provide an insightful understanding of possible obstacles when using MICP to stabilize organic soils.

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Innovative methods of ground improvement for railway embankment peat fens foundation soil

Cited by 15 publications

References 40 publications

Effect of Scallop Powder Addition on MICP Treatment of Amorphous Peat

Effect of Scallop Powder Addition on MICP Treatment of Amorphous Peat

Towards the Development of Sustainable Ground Improvement Techniques—Biocementation Study of an Organic Soil

Influence of humic acid on microbial induced carbonate precipitation for organic soil improvement

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