Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vi...Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vironment and intensify carbon emissions.However,the use of microbially induced calcium carbonate pre-cipitation(MICP)to obtain bio-cement is a novel technique with the potential to induce soil stability,providing a low-carbon,environment-friendly,and sustainable integrated solution for some geotechnical engineering pro-blems in the environment.This paper presents a comprehensive review of the latest progress in soil improvement based on the MICP strategy.It systematically summarizes and overviews the mineralization mechanism,influ-encing factors,improved methods,engineering characteristics,and current field application status of the MICP.Additionally,it also explores the limitations and correspondingly proposes prospective applications via the MICP approach for soil improvement.This review indicates that the utilization of different environmental calcium-based wastes in MICP and combination of materials and MICP are conducive to meeting engineering and market demand.Furthermore,we recommend and encourage global collaborative study and practice with a view to commercializing MICP technique in the future.The current review purports to provide insights for engineers and interdisciplinary researchers,and guidance for future engineering applications.展开更多
Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an...Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.展开更多
The complex and diverse nature of coal mining sites,including different landforms and working conditions,presents challenges for rehabilitation efforts.To address this,we conducted a comprehensive experimental study f...The complex and diverse nature of coal mining sites,including different landforms and working conditions,presents challenges for rehabilitation efforts.To address this,we conducted a comprehensive experimental study focusing on microbially induced calcium carbonate precipitation(MICP)remediation,considering the fracture characteristics of coal mining sites.The MICP-restored samples were subjected to confined/unconfined compressive strength,uniaxial/triaxial permeability,and souring tests to assess their restoration efficacy.The results showed that under similar mining conditions,the average depth of parallel fractures was 0.185 m for loess ridges,0.16 m for the valley,and 0.146 m for the blown-sand region,while the average depth for boundary fractures was 0.411 m for loess ridges,0.178 m for the valley,and 0.268 m for the blown-sand region.Notably,parallel fractures showed negligible filling in all landforms,whereas boundary fractures in the blown-sand region were completely filled with wind-deposited sand.The valley landform was filled with alluvium and wind-deposited sand,whereas the loess landform was filled with wind-deposited sand and loess.MICP-restored soil samples in all landforms achieved a strength comparable to remolded fracture-free soil samples.Across all landforms,the maximum permeability coefficient of MICP-restored soil samples closely matched that of remolded fracture-free soil samples.Under similar topographic and rainfall conditions MICP restorations scoured 31.3 g on blown-sand region,19.3 g on loess ridges,and 17.6 g on valleys.These research findings provide an experimental foundation for MICP repair of coal mining ground fractures.展开更多
基金funded by the National Natural Science Foundation of China(No.41962016)the Natural Science Foundation of NingXia(Nos.2023AAC02023,2023A1218,and 2021AAC02006).
文摘Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vironment and intensify carbon emissions.However,the use of microbially induced calcium carbonate pre-cipitation(MICP)to obtain bio-cement is a novel technique with the potential to induce soil stability,providing a low-carbon,environment-friendly,and sustainable integrated solution for some geotechnical engineering pro-blems in the environment.This paper presents a comprehensive review of the latest progress in soil improvement based on the MICP strategy.It systematically summarizes and overviews the mineralization mechanism,influ-encing factors,improved methods,engineering characteristics,and current field application status of the MICP.Additionally,it also explores the limitations and correspondingly proposes prospective applications via the MICP approach for soil improvement.This review indicates that the utilization of different environmental calcium-based wastes in MICP and combination of materials and MICP are conducive to meeting engineering and market demand.Furthermore,we recommend and encourage global collaborative study and practice with a view to commercializing MICP technique in the future.The current review purports to provide insights for engineers and interdisciplinary researchers,and guidance for future engineering applications.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(No.52279097,No.51779264)Blue and Green Project of Jiangsu Province.
文摘Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.
基金funded by Guizhou Provincial Science and Technology Project,Qiankehejichu-ZK[2022]-YB529Guizhou Education Department(Youth Science and Technology Topnotch Talent Project)QJJ[2024]345+1 种基金Guizhou Provincial Science and Technology Project,QKHJC-ZK[2023]-YBGuizhou Education Department Youth Science and Technology Talents Growth Project,QJHKY[2020]122.
文摘The complex and diverse nature of coal mining sites,including different landforms and working conditions,presents challenges for rehabilitation efforts.To address this,we conducted a comprehensive experimental study focusing on microbially induced calcium carbonate precipitation(MICP)remediation,considering the fracture characteristics of coal mining sites.The MICP-restored samples were subjected to confined/unconfined compressive strength,uniaxial/triaxial permeability,and souring tests to assess their restoration efficacy.The results showed that under similar mining conditions,the average depth of parallel fractures was 0.185 m for loess ridges,0.16 m for the valley,and 0.146 m for the blown-sand region,while the average depth for boundary fractures was 0.411 m for loess ridges,0.178 m for the valley,and 0.268 m for the blown-sand region.Notably,parallel fractures showed negligible filling in all landforms,whereas boundary fractures in the blown-sand region were completely filled with wind-deposited sand.The valley landform was filled with alluvium and wind-deposited sand,whereas the loess landform was filled with wind-deposited sand and loess.MICP-restored soil samples in all landforms achieved a strength comparable to remolded fracture-free soil samples.Across all landforms,the maximum permeability coefficient of MICP-restored soil samples closely matched that of remolded fracture-free soil samples.Under similar topographic and rainfall conditions MICP restorations scoured 31.3 g on blown-sand region,19.3 g on loess ridges,and 17.6 g on valleys.These research findings provide an experimental foundation for MICP repair of coal mining ground fractures.
