Microbially mediated dissimilatory reduction of nitrate, or denitrification, offers the promise f... more Microbially mediated dissimilatory reduction of nitrate, or denitrification, offers the promise for non-disruptive mitigation of the potential for earthquake-induced liquefaction beneath existing facilities. Denitrification can mitigate liquefaction in two ways: by desaturation of the soil through generation of gas and by cementation of the soil through precipitation of calcium carbonate as calcite. Laboratory column tests demonstrate that desaturation via biogenic gas occurs almost immediately upon stimulation of the denitrifying microbes, providing short term mitigation while calcite is being precipitated. Once enough calcite is precipitated, denitrification provides long term mitigation. Laboratory simple shear testing demonstrates that a relatively small decrease in the degree of saturation, as little as 5%, and a relatively small amount of calcite precipitation, as little as 0.4 percent of the dry weight of the soil, can both provide substantial mitigation of liquefaction poten...
Abstract The pullout resistance of a geosynthetic reinforcement is crucial for the design of rein... more Abstract The pullout resistance of a geosynthetic reinforcement is crucial for the design of reinforced soil structures. In this paper, an innovative concept, biocementation-geosynthetic (BG) system is presented, in which biocementation is used in combination with geosynthetic to increase the pullout resistance of the geosynthetic reinforcement. A series of pullout tests were conducted in laboratory to obtain the pullout behavior of the biocementation-geosynthetic system. From the pullout test results, it was found that the BG system was more efficient in enhancing the pullout resistant as compared with the ordinary geosynthetic (OG) system. For both geosynthetic strips and biaxial geogrid, the BG system had a higher pullout resistance at various levels of relative density. The BG system with only about 0.65% calcite produced by the biocementation process has a 13%–38% improvement in the pullout resistance compared to the OG system. In addition, the interface shear strength parameters (the adhesion ca and average interface friction angle ϕ) of the BG system are also higher than that of the corresponding OG system in most cases, indicating the better interface performance of the BG system.
In order to reclaim ultra-soft tailings (e.g. oil sands) ponds great amount of research and techn... more In order to reclaim ultra-soft tailings (e.g. oil sands) ponds great amount of research and technology work has been performed over the years to optimize the dewatering and consolidation of Fine Fluid Tailings (FFT), including the use of different chemical flocculants and mechanical deposition approaches. Yet, traditionally flocculation, hence settling, and consolidation are treated as two independent processes. Here integrate these two processes, proving how implementation of certain types of flocculants influences the consolidation rates and strength of the deposit. Laboratory studies on small scale settling columns carried out at Deltares tested the settling and consolidation rates, and the strength development of FFT samples treated with different flocculants dosage under different water chemistry and pH conditions. These systematic tests revealed distinct correlations between flocculation and consolidation and strength properties. These studies also enabled us to find specific ...
The mechanical properties of calcium carbonate minerals formed by enzyme-induced carbonate precip... more The mechanical properties of calcium carbonate minerals formed by enzyme-induced carbonate precipitation (EICP) were studied using nanoindentation. Two types of precipitates were considered: (i) a “baseline” precipitate, synthesized via urea hydrolysis in an aqueous solution of urease enzyme, urea, and calcium chloride; and (ii) a “modified” precipitate, synthesized from a similar solution, but with the inclusion of nonfat dry milk. While both precipitates predominantly comprised calcite, X-ray diffraction and Raman spectroscopy indicated broader peaks in the modified precipitate, implying differences in the crystal structure of the two precipitates. Both precipitates were polycrystalline and had a higher average indentation hardness (H) and a lower indentation modulus (M) compared with the values for single calcite crystals reported in the literature. The ductility of the precipitates was quantified by the ratio M/H. The modified precipitate had a higher average M/H, implying great...
International Journal of Geosynthetics and Ground Engineering, 2021
A feasibility study was performed to assess the potential of microbially induced desaturation and... more A feasibility study was performed to assess the potential of microbially induced desaturation and precipitation (MIDP) through denitrification to reduce the risk of earthquake-induced liquefaction and improve the resilience of embankments along the lower Fraser River in Richmond, British Columbia, Canada. The denitrification process produces nitrogen gas, which gradually desaturates the soil, and dissolved inorganic carbon, which in presence of dissolved calcium results in precipitation of calcium carbonate minerals, cementing the soil particles. The trapped gas bubbles dampens pore pressure build-up during cyclic loading. Consequently, microbially induced desaturation (MID) the first phase of the MIDP process, has great potential as soil improvement technique, especially for liquefaction mitigation, independently from the precipitation phase of the process. Numerous studies have demonstrated the effect of biogenic gas formation on the mechanical response for treated sand samples at...
There has been increasing interest, in the past decade, in bio-mediated approaches to soil improv... more There has been increasing interest, in the past decade, in bio-mediated approaches to soil improvement for geotechnical applications. Microbially induced calcium carbonate precipitation (MICP) has been investigated as a potentially sustainable method for the strengthening and stabilisation of soil structures. This paper presents the results of a study on the effect of jute fibres on both the MICP process and properties of biocemented sand. Ureolytic Sporosarcina pasteurii has been used to produce biocemented soil columns via MICP in the laboratory. Results showed that columns containing 0.75% (by weight of sand) untreated jute fibres had unconfined compressive strengths approximately six times greater on average compared to biocemented sand columns without jute fibres. Furthermore, efficiency of chemical conversion was found to be higher in columns containing jute fibres, as measured using ion chromatography. Columns containing jute had calcimeter measured CaCO3 contents at least th...
Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 2009
The precipitation of calcium carbonate is well studied in many fields of research and industry. D... more The precipitation of calcium carbonate is well studied in many fields of research and industry. Despite the fact that, or perhaps because of the fact that, it is well studied in many fields, different approaches have been used to describe the kinetics of the precipitation process. The aim of this study was to collect and compare the data available in the literature and find a consistent method to describe the kinetics of growth and nucleation of the various polymorphs of calcium carbonate. Inventory of the available data showed that a significant number of the literature sources were incomplete in providing the required information to recalculate the kinetic constants. Using a unified method, we obtained a unique set of parameters to describe the kinetics for growth for calcite, vaterite and amorphous calcium carbonate (ACC) and nucleation for vaterite and ACC. Recalculation of the kinetic constants demonstrated that calcite confirmed there are two growth mechanisms within one polym...
Microbially mediated dissimilatory reduction of nitrate, or denitrification, offers the promise f... more Microbially mediated dissimilatory reduction of nitrate, or denitrification, offers the promise for non-disruptive mitigation of the potential for earthquake-induced liquefaction beneath existing facilities. Denitrification can mitigate liquefaction in two ways: by desaturation of the soil through generation of gas and by cementation of the soil through precipitation of calcium carbonate as calcite. Laboratory column tests demonstrate that desaturation via biogenic gas occurs almost immediately upon stimulation of the denitrifying microbes, providing short term mitigation while calcite is being precipitated. Once enough calcite is precipitated, denitrification provides long term mitigation. Laboratory simple shear testing demonstrates that a relatively small decrease in the degree of saturation, as little as 5%, and a relatively small amount of calcite precipitation, as little as 0.4 percent of the dry weight of the soil, can both provide substantial mitigation of liquefaction poten...
Abstract The pullout resistance of a geosynthetic reinforcement is crucial for the design of rein... more Abstract The pullout resistance of a geosynthetic reinforcement is crucial for the design of reinforced soil structures. In this paper, an innovative concept, biocementation-geosynthetic (BG) system is presented, in which biocementation is used in combination with geosynthetic to increase the pullout resistance of the geosynthetic reinforcement. A series of pullout tests were conducted in laboratory to obtain the pullout behavior of the biocementation-geosynthetic system. From the pullout test results, it was found that the BG system was more efficient in enhancing the pullout resistant as compared with the ordinary geosynthetic (OG) system. For both geosynthetic strips and biaxial geogrid, the BG system had a higher pullout resistance at various levels of relative density. The BG system with only about 0.65% calcite produced by the biocementation process has a 13%–38% improvement in the pullout resistance compared to the OG system. In addition, the interface shear strength parameters (the adhesion ca and average interface friction angle ϕ) of the BG system are also higher than that of the corresponding OG system in most cases, indicating the better interface performance of the BG system.
In order to reclaim ultra-soft tailings (e.g. oil sands) ponds great amount of research and techn... more In order to reclaim ultra-soft tailings (e.g. oil sands) ponds great amount of research and technology work has been performed over the years to optimize the dewatering and consolidation of Fine Fluid Tailings (FFT), including the use of different chemical flocculants and mechanical deposition approaches. Yet, traditionally flocculation, hence settling, and consolidation are treated as two independent processes. Here integrate these two processes, proving how implementation of certain types of flocculants influences the consolidation rates and strength of the deposit. Laboratory studies on small scale settling columns carried out at Deltares tested the settling and consolidation rates, and the strength development of FFT samples treated with different flocculants dosage under different water chemistry and pH conditions. These systematic tests revealed distinct correlations between flocculation and consolidation and strength properties. These studies also enabled us to find specific ...
The mechanical properties of calcium carbonate minerals formed by enzyme-induced carbonate precip... more The mechanical properties of calcium carbonate minerals formed by enzyme-induced carbonate precipitation (EICP) were studied using nanoindentation. Two types of precipitates were considered: (i) a “baseline” precipitate, synthesized via urea hydrolysis in an aqueous solution of urease enzyme, urea, and calcium chloride; and (ii) a “modified” precipitate, synthesized from a similar solution, but with the inclusion of nonfat dry milk. While both precipitates predominantly comprised calcite, X-ray diffraction and Raman spectroscopy indicated broader peaks in the modified precipitate, implying differences in the crystal structure of the two precipitates. Both precipitates were polycrystalline and had a higher average indentation hardness (H) and a lower indentation modulus (M) compared with the values for single calcite crystals reported in the literature. The ductility of the precipitates was quantified by the ratio M/H. The modified precipitate had a higher average M/H, implying great...
International Journal of Geosynthetics and Ground Engineering, 2021
A feasibility study was performed to assess the potential of microbially induced desaturation and... more A feasibility study was performed to assess the potential of microbially induced desaturation and precipitation (MIDP) through denitrification to reduce the risk of earthquake-induced liquefaction and improve the resilience of embankments along the lower Fraser River in Richmond, British Columbia, Canada. The denitrification process produces nitrogen gas, which gradually desaturates the soil, and dissolved inorganic carbon, which in presence of dissolved calcium results in precipitation of calcium carbonate minerals, cementing the soil particles. The trapped gas bubbles dampens pore pressure build-up during cyclic loading. Consequently, microbially induced desaturation (MID) the first phase of the MIDP process, has great potential as soil improvement technique, especially for liquefaction mitigation, independently from the precipitation phase of the process. Numerous studies have demonstrated the effect of biogenic gas formation on the mechanical response for treated sand samples at...
There has been increasing interest, in the past decade, in bio-mediated approaches to soil improv... more There has been increasing interest, in the past decade, in bio-mediated approaches to soil improvement for geotechnical applications. Microbially induced calcium carbonate precipitation (MICP) has been investigated as a potentially sustainable method for the strengthening and stabilisation of soil structures. This paper presents the results of a study on the effect of jute fibres on both the MICP process and properties of biocemented sand. Ureolytic Sporosarcina pasteurii has been used to produce biocemented soil columns via MICP in the laboratory. Results showed that columns containing 0.75% (by weight of sand) untreated jute fibres had unconfined compressive strengths approximately six times greater on average compared to biocemented sand columns without jute fibres. Furthermore, efficiency of chemical conversion was found to be higher in columns containing jute fibres, as measured using ion chromatography. Columns containing jute had calcimeter measured CaCO3 contents at least th...
Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 2009
The precipitation of calcium carbonate is well studied in many fields of research and industry. D... more The precipitation of calcium carbonate is well studied in many fields of research and industry. Despite the fact that, or perhaps because of the fact that, it is well studied in many fields, different approaches have been used to describe the kinetics of the precipitation process. The aim of this study was to collect and compare the data available in the literature and find a consistent method to describe the kinetics of growth and nucleation of the various polymorphs of calcium carbonate. Inventory of the available data showed that a significant number of the literature sources were incomplete in providing the required information to recalculate the kinetic constants. Using a unified method, we obtained a unique set of parameters to describe the kinetics for growth for calcite, vaterite and amorphous calcium carbonate (ACC) and nucleation for vaterite and ACC. Recalculation of the kinetic constants demonstrated that calcite confirmed there are two growth mechanisms within one polym...
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