Biostimulation has been proven to be an available approach for microbially induced calcium carbonate precipitation(MICP).However,biostimulation may not be as effective as bioaugmentation in some unfavorable situations...Biostimulation has been proven to be an available approach for microbially induced calcium carbonate precipitation(MICP).However,biostimulation may not be as effective as bioaugmentation in some unfavorable situations.In this study,the feasibility of biochar-assisted MICP for improving the shear strength of calcareous sand is investigated.The optimization of cementation solution for biostimulated MICP is first determined through a series of unconfined compressive tests.The shear characteristics of biocemented calcareous sand,enhanced by biochar and treated through biostimulation,are then assessed using consolidated undrained(CU)shear triaxial tests.To characterize the shear strength of biocemented sand under low effective normal stress,both Mohr-Coulomb failure envelopes and nonlinear failure envelopes were employed.Meanwhile,the current study also compared and analyzed two distinct stress states:maximum principal stress ratio(σ'_(1)/σ'_(3)max)and Skempton’s pore pressure parameter A=0,to identify an appropriate failure criterion for determination of the shear strength parameters.Furthermore,the microscopic features and post-failure characteristics of biochar-assisted calcareous sand were examined and discussed.The findings indicate that biochar can contribute to an increase in cementation content by serving as additional nucleation sites.The study may provide valuable insights into the potential of biochar-assisted MICP for enhancing the biostimulation approach.展开更多
Calcareous sand is widely present in coastal areas around the world and is usually considered as a weak and unstable material due to its high compressibility and low strength.Microbial-induced calcium carbonate precip...Calcareous sand is widely present in coastal areas around the world and is usually considered as a weak and unstable material due to its high compressibility and low strength.Microbial-induced calcium carbonate precipitation(MICP)is a promising technique for soil improvement.However,the commonly adopted bio-augmented MICP approach is in general less compatible with the natural soil environment.Thus,this study focuses on the bio-stimulated MICP approach,which is likely to enhance the dominance of ureolytic bacteria for longer period and thus is deemed more efficient.The main objective of this paper is to investigate the compressibility of calcareous sand treated by bio-stimulated MICP approach.In the current study,a series of one-dimension compression tests was conducted on bio-cemented sand pre-pared via bio-stimulation with different initial relative densities(D r).Based on the obtained compression curves and particle size distribution(PSD)curves,the parameters including cementation content,the coefficient of compressibility(a v),PSD,relative breakage(B r),and relative agglomeration(A r)were discussed.The results showed that a v decreased with the increasing cementation content.The bio-cemented sand prepared with higher initial D r had smaller(approximately 20%e70%)a v values than that with lower initial D r.The specimen with higher initial D r and higher cementation content resulted in smaller B r but larger A r.Finally,a conceptual framework featuring multiple contact and damage modes was proposed.展开更多
Coral sand is widely encountered in coastal areas of tropical and subtropical regions.Compared with silica sand,it usually exhibits weaker performance from the perspective of engineering geology.To improve the geomech...Coral sand is widely encountered in coastal areas of tropical and subtropical regions.Compared with silica sand,it usually exhibits weaker performance from the perspective of engineering geology.To improve the geomechanical performance of coral sand and meet the requirement of foundation construction in coastal areas,a novel alkali activation-based sustainable binder was developed.The alkaliactivated slag(AAS)binder material was composed of ground granulated blast-furnace slag(GGBS)and hydrated lime with the amendment of biochar,an agricultural waste-derived material.The biocharamended AAS stabilized coral sand was subjected to a series of laboratory tests to determine its mechanical,physicochemical,and microstructural characteristics.Results show that adding a moderate amount of biochar in AAS could improve soil strength,elastic modulus,and water holding capacity by up to 20%,70%,and 30%,respectively.Moreover,the addition of biochar in AAS had a marginal effect on the sulfate resistance of the stabilized sand,especially at high biochar content.However,the resistance of the AAS stabilized sand to wet-dry cycles slightly deteriorated with the addition of biochar.Based on these observations,a conceptual model showing biochar-AAS-sand interactions was proposed,in which biochar served as an internal curing agent,micro-reinforcer,and mechanically weak point.展开更多
This paper builds on exploring the applications of biomediated pathways to solve geotechnical challenges.First,the state of the art of biological remediation strategies including microbial remediation and phytoremedia...This paper builds on exploring the applications of biomediated pathways to solve geotechnical challenges.First,the state of the art of biological remediation strategies including microbial remediation and phytoremediation have been introduced and critically reviewed in the context of decontaminating the soils.Next,biopolymerisation,biomineralisation and bioneutralisation processes have been depicted with a special emphasis on the applications including but not limited to soil stabilisation,soil erosion prevention,anti-desertification and pH neutralisation.Each of these methods have their own limitations and bottlenecks while scaling up,and these challenges have been summarised and some possible paths to overcome the challenges have also been discussed.The state of the art of electromagnetic(EM)monitoring methods to capture the effects of biomediation on spatio-temporal soil properties are then highlighted as a non-invasive and rapid pathway to track the progress of biomediated soil processes.Finally,each of the technologies discussed have been evaluated for their maturity level using the principles of technology readiness level(TRL).A majority of the technologies amounting to around 77%are still in the TRL 4e7,i.e.in the valley of death.It is thus evident that development of these technologies needs to be supported with appropriate funding for improving their maturity to a level of industrial deployment.展开更多
In this review paper,the applications of biomineralization in environmental geotechnics are analyzed.Three environmental geotechnics scenarios,namely heavy metal contamination immobilization and removal,waste and CO_(...In this review paper,the applications of biomineralization in environmental geotechnics are analyzed.Three environmental geotechnics scenarios,namely heavy metal contamination immobilization and removal,waste and CO_(2)containment,and recycled use of industrial byproducts,are discussed and evaluated regarding current trends and prospects.The biomineralization process,specifically the Microbially Induced Carbonate Precipitation(MICP)technology,is an effective solution for immobilizing heavy metals through co-precipitation with calcium carbonate,with successful results in cleaning up contaminated soils.The nature of biomineralization enhances earth material strength and decreases permeability,making it suitable for waste and CO_(2)containment.Additionally,using industrial byproducts in MICP technology can improve the physical,mechanical,and hydraulic properties of earth materials,making it a potential solution for efficient waste utilization.In conclusion,the applications of biomineralization in environmental geotechnics hold great promise for solving various environmental problems.However,further research is needed to better understand the control and consistency of biomineralization processes,the durability of biominerals,the scale of applications,and environmental concerns.展开更多
The application of microbially induced carbonate precipitation(MICP)in clayey soils has attracted much attention,and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils....The application of microbially induced carbonate precipitation(MICP)in clayey soils has attracted much attention,and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils.Within the sand-clay-bacteria-calcite system,the property and content of clay play crucial roles in affecting bacterial growth and calcite formation.More important,bentonite is particularly sensitive to changes in the geochemical environment.In this study,the sand-bentonite mixtures were treated by biostimulated MICP,aiming to provide insights into the behavior of this system.The bacterial activity and cementation pattern at different bentonite contents were evaluated through a series of tests such as enrichment tests,unconfined compressive strength(UCS)tests,cementation content measurements,mercury intrusion porosimetry(MIP)tests,scanning electron microscopy(SEM)observations,and energy dispersive X-ray spectroscopy(EDS)analyses.The findings showed that the bentonite presence promoted the enrichment of indigenous ureolytic bacteria,with lower bentonite levels enhancing ureolytic activity.Macroscopic and microscopic characterization indicated that the bentonite-coating sand structure was more conducive to the formation of large-sized calcite crystals capable of cementing soil particles compared to sand-supported and bentonite-supported structures.Additionally,excessive calcium ions(Ca^(2+))concentrations in the cementitious solution would lead to predominant calcite deposition on soil particle surfaces,contributing minimally to strength improvement.展开更多
基金financially supported by the Natural Science Foundation of China(Grant Nos.42377166 and 42007246)Key R&D Program Social Development Project of Jiangsu Province(Grant No.BE2023800)the National Key R&D Program of China(Grant No.2023YFC3709600).
文摘Biostimulation has been proven to be an available approach for microbially induced calcium carbonate precipitation(MICP).However,biostimulation may not be as effective as bioaugmentation in some unfavorable situations.In this study,the feasibility of biochar-assisted MICP for improving the shear strength of calcareous sand is investigated.The optimization of cementation solution for biostimulated MICP is first determined through a series of unconfined compressive tests.The shear characteristics of biocemented calcareous sand,enhanced by biochar and treated through biostimulation,are then assessed using consolidated undrained(CU)shear triaxial tests.To characterize the shear strength of biocemented sand under low effective normal stress,both Mohr-Coulomb failure envelopes and nonlinear failure envelopes were employed.Meanwhile,the current study also compared and analyzed two distinct stress states:maximum principal stress ratio(σ'_(1)/σ'_(3)max)and Skempton’s pore pressure parameter A=0,to identify an appropriate failure criterion for determination of the shear strength parameters.Furthermore,the microscopic features and post-failure characteristics of biochar-assisted calcareous sand were examined and discussed.The findings indicate that biochar can contribute to an increase in cementation content by serving as additional nucleation sites.The study may provide valuable insights into the potential of biochar-assisted MICP for enhancing the biostimulation approach.
基金This study was financially supported by the Natural Science Foundation of China(Grant No.42007246)the Fundamental Research Funds for the Central Universities(Grant No.2242022k30055)Indo-U.S.Science and Technology Forum(Grant No.IUSSTF/AUG/JC/047/2018).
文摘Calcareous sand is widely present in coastal areas around the world and is usually considered as a weak and unstable material due to its high compressibility and low strength.Microbial-induced calcium carbonate precipitation(MICP)is a promising technique for soil improvement.However,the commonly adopted bio-augmented MICP approach is in general less compatible with the natural soil environment.Thus,this study focuses on the bio-stimulated MICP approach,which is likely to enhance the dominance of ureolytic bacteria for longer period and thus is deemed more efficient.The main objective of this paper is to investigate the compressibility of calcareous sand treated by bio-stimulated MICP approach.In the current study,a series of one-dimension compression tests was conducted on bio-cemented sand pre-pared via bio-stimulation with different initial relative densities(D r).Based on the obtained compression curves and particle size distribution(PSD)curves,the parameters including cementation content,the coefficient of compressibility(a v),PSD,relative breakage(B r),and relative agglomeration(A r)were discussed.The results showed that a v decreased with the increasing cementation content.The bio-cemented sand prepared with higher initial D r had smaller(approximately 20%e70%)a v values than that with lower initial D r.The specimen with higher initial D r and higher cementation content resulted in smaller B r but larger A r.Finally,a conceptual framework featuring multiple contact and damage modes was proposed.
基金supported by the Hawaii Department of Transportation(Grant No.2020-4ReSUPP)National Natural Science Foundation of China(Grant No.42007246)Fundamental Research Funds for the Central Universities.
文摘Coral sand is widely encountered in coastal areas of tropical and subtropical regions.Compared with silica sand,it usually exhibits weaker performance from the perspective of engineering geology.To improve the geomechanical performance of coral sand and meet the requirement of foundation construction in coastal areas,a novel alkali activation-based sustainable binder was developed.The alkaliactivated slag(AAS)binder material was composed of ground granulated blast-furnace slag(GGBS)and hydrated lime with the amendment of biochar,an agricultural waste-derived material.The biocharamended AAS stabilized coral sand was subjected to a series of laboratory tests to determine its mechanical,physicochemical,and microstructural characteristics.Results show that adding a moderate amount of biochar in AAS could improve soil strength,elastic modulus,and water holding capacity by up to 20%,70%,and 30%,respectively.Moreover,the addition of biochar in AAS had a marginal effect on the sulfate resistance of the stabilized sand,especially at high biochar content.However,the resistance of the AAS stabilized sand to wet-dry cycles slightly deteriorated with the addition of biochar.Based on these observations,a conceptual model showing biochar-AAS-sand interactions was proposed,in which biochar served as an internal curing agent,micro-reinforcer,and mechanically weak point.
文摘This paper builds on exploring the applications of biomediated pathways to solve geotechnical challenges.First,the state of the art of biological remediation strategies including microbial remediation and phytoremediation have been introduced and critically reviewed in the context of decontaminating the soils.Next,biopolymerisation,biomineralisation and bioneutralisation processes have been depicted with a special emphasis on the applications including but not limited to soil stabilisation,soil erosion prevention,anti-desertification and pH neutralisation.Each of these methods have their own limitations and bottlenecks while scaling up,and these challenges have been summarised and some possible paths to overcome the challenges have also been discussed.The state of the art of electromagnetic(EM)monitoring methods to capture the effects of biomediation on spatio-temporal soil properties are then highlighted as a non-invasive and rapid pathway to track the progress of biomediated soil processes.Finally,each of the technologies discussed have been evaluated for their maturity level using the principles of technology readiness level(TRL).A majority of the technologies amounting to around 77%are still in the TRL 4e7,i.e.in the valley of death.It is thus evident that development of these technologies needs to be supported with appropriate funding for improving their maturity to a level of industrial deployment.
基金supported by the Natural Science Foundation of China(42007246)and the Fundamental Research Funds for the Central Universities.
文摘In this review paper,the applications of biomineralization in environmental geotechnics are analyzed.Three environmental geotechnics scenarios,namely heavy metal contamination immobilization and removal,waste and CO_(2)containment,and recycled use of industrial byproducts,are discussed and evaluated regarding current trends and prospects.The biomineralization process,specifically the Microbially Induced Carbonate Precipitation(MICP)technology,is an effective solution for immobilizing heavy metals through co-precipitation with calcium carbonate,with successful results in cleaning up contaminated soils.The nature of biomineralization enhances earth material strength and decreases permeability,making it suitable for waste and CO_(2)containment.Additionally,using industrial byproducts in MICP technology can improve the physical,mechanical,and hydraulic properties of earth materials,making it a potential solution for efficient waste utilization.In conclusion,the applications of biomineralization in environmental geotechnics hold great promise for solving various environmental problems.However,further research is needed to better understand the control and consistency of biomineralization processes,the durability of biominerals,the scale of applications,and environmental concerns.
基金supported by the Key R&D Program Social Development Project of Jiangsu Province(Grant No.BE2023800)the Natural Science Foundation of China(Grant No.42377166)the National Key R&D Program of China(Grant No.2023YFC3709600)。
文摘The application of microbially induced carbonate precipitation(MICP)in clayey soils has attracted much attention,and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils.Within the sand-clay-bacteria-calcite system,the property and content of clay play crucial roles in affecting bacterial growth and calcite formation.More important,bentonite is particularly sensitive to changes in the geochemical environment.In this study,the sand-bentonite mixtures were treated by biostimulated MICP,aiming to provide insights into the behavior of this system.The bacterial activity and cementation pattern at different bentonite contents were evaluated through a series of tests such as enrichment tests,unconfined compressive strength(UCS)tests,cementation content measurements,mercury intrusion porosimetry(MIP)tests,scanning electron microscopy(SEM)observations,and energy dispersive X-ray spectroscopy(EDS)analyses.The findings showed that the bentonite presence promoted the enrichment of indigenous ureolytic bacteria,with lower bentonite levels enhancing ureolytic activity.Macroscopic and microscopic characterization indicated that the bentonite-coating sand structure was more conducive to the formation of large-sized calcite crystals capable of cementing soil particles compared to sand-supported and bentonite-supported structures.Additionally,excessive calcium ions(Ca^(2+))concentrations in the cementitious solution would lead to predominant calcite deposition on soil particle surfaces,contributing minimally to strength improvement.
