The biocemented coral sand pile composite foundation represents an innovative foundation improvement technology,utilizing Microbially Induced Carbonate Precipitation(MICP)to consolidate a specific volume of coral sand...The biocemented coral sand pile composite foundation represents an innovative foundation improvement technology,utilizing Microbially Induced Carbonate Precipitation(MICP)to consolidate a specific volume of coral sand within the foundation into piles with defined strength,thereby enabling them to collaboratively bear external loads with the surrounding unconsolidated coral sand.In this study,a series of shaking table model tests were conducted to explore the dynamic response of the biocemented coral sand pile composite foundation under varying seismic wave types and peak accelerations.The surface macroscopic phenomena,excess pore water pressure ratio,acceleration response,and vertical settlement were measured and analysed in detail.Test results show that seismic wave types play a decisive role in the macroscopic surface phenomena and the response of the excess pore water pressure ratio.The cumulative settlement of the upper structure under the action of Taft waves was about 1.5 times that of El Centro waves and Kobe waves.The most pronounced liquefaction phenomena were recorded under the Taft wave,followed by the El Centro wave,and subsequently the Kobe wave.An observed positive correlation was established between the liquefaction phenomenon and the Aristotelian in-tensity of the seismic waves.However,variations in seismic wave types exerted minimal influence on the ac-celeration amplification factor of the coral sand foundation.Analysis of the acceleration amplification factor revealed a triphasic pattern-initially increasing,subsequently decreasing,and finally increasing again-as burial depth increased,in relation to the peak value of the input acceleration.This study confirms that the biocemented coral sand pile composite foundation can effectively enhance the liquefaction resistance of coral sand foundations..展开更多
It is difficult to collect and characterise well-preserved samples of weakly-cemented granular rocks as conventional sampling techniques often result in destruction of the cementation.An alternative approach is to pre...It is difficult to collect and characterise well-preserved samples of weakly-cemented granular rocks as conventional sampling techniques often result in destruction of the cementation.An alternative approach is to prepare synthetic geomaterials to match required specifications.This paper introduces microbially induced carbonate precipitation(MICP)as a method to reliably deliver artificiallycemented specimens with customised properties,closely resembling those of soft carbonate sandstones.The specimens are generated from materials with two highly different particle size distributions(PSDs)to access a range of achievable combinations of strengths and porosities.The MICP parameters are kept constant across all samples to obtain similar calcium carbonate characteristics(size of individual crystals,type,etc.),while injected volume is varied to achieve different cementation levels.Although uniform cementation of very coarse sands has been considered very difficult to achieve,the results show that both the fine and coarse sand specimens present high degrees of uniformity and a good degree of repeatability.The unconfined compressive strengths(UCSs)(less than 3000 kPa)and porosities(0.25e0.4)of the artificial specimens fall in the same range of values reported for natural rocks.The strength gainwas greater in the fine sand than that in the coarse sand,as the void size in the latter was significantly larger compared to the calcium carbonate crystals’size,resulting in precipitation on less effective locations,away from contacts between particles.The strengths and porosities obtained for the two sands in this work fall within ranges reported in the literature for natural soft rocks,demonstrating theMICP technique is able to achieve realistic properties and may be used to produce a full range of properties by varying the grain sizes,and possibly the width of PSD.展开更多
This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement tech...This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement technique,which is used in Civil Engineering applications to produce calcium carbonate through bacterial or enzymatic activity,replacing the use of other binder materials such as cement or resins,and therefore reducing carbon footprint.The microdevice was used to measure urease activity in the soil interstitial fluid,to investigate if bacterial activity could be affected by the presence of the particles and tortuosity from pore geometry.Such analysis is important to understand biocementation mechanism inside the soil and helps to improve the design of such treatment solutions.The device is basically a squared reservoir printed in polypropylene using a 3D printing machine,incorporating stainless steel electrodes in its base.The electrical resistivity was computed adopting Wenner method,by connecting 4 PCB electrodes to a signal generator and an oscilloscope for measuring the voltage when a AC current of 1 mA was applied.Both square and sinusoidal waves with 5 kHz frequency were selected among other frequencies.The measurements were adjusted during the calibration of the microdevice,done using standard salt solutions with known electrical conductivity measured using an electrical conductivity probe.For the bacterial activity measurements,the bacterial and urea solutions were added to a uniform-graded size quarzitic sand(average diameter 0.3 mm)placed inside the microdevice and covering completely the electrodes.Bacterial activity was not affected by the presence of the sand,which confirms that this treatment is effective for this type of soils.展开更多
Biomineralization through microbial process has attracted great attention in the field of geotechnical engineering due to its ability to bind granular materials,clog pores,and seal fractures.Although minerals formed b...Biomineralization through microbial process has attracted great attention in the field of geotechnical engineering due to its ability to bind granular materials,clog pores,and seal fractures.Although minerals formed by biomineralization are generally the same as that by mineralization,their mechanical behaviors show a significant discrepancy.This study aims to figure out the differences between biomineralization and mineralization processes by visualizing and tracking the formation of minerals using microfluidics.Both biomineralization and mineralization processes occurred in the Y-shaped sandcontaining microchip that mimics the underground sand layers.Images from different areas in the reaction microchannel of microchips were captured to directly compare the distribution of minerals.Crystal size and numbers from different reaction times were measured to quantify the differences between biomineralization and mineralization processes in terms of crystal kinetics.Results showed that the crystals were precipitated in a faster and more uncontrollable manner in the mineralization process than that in the biomineralization process,given that those two processes presented similar precipitation stages.In addition,a more heterogeneous distribution of crystals was observed during the biomineralization process.The precipitation behaviors were further explained by the classical nucleation crystal growth theory.The present microfluidic tests could advance the understanding of biomineralization and provide new insight into the optimization of biocementation technology.展开更多
Geomaterials with inferior hydraulic and strength characteristics often need improvement to enhance their engineering behaviors.Traditional ground improvement techniques require enormous mechanical effort or synthetic...Geomaterials with inferior hydraulic and strength characteristics often need improvement to enhance their engineering behaviors.Traditional ground improvement techniques require enormous mechanical effort or synthetic chemicals.Sustainable stabilization technique such as microbially induced calcite precipitation(MICP)utilizes bacterial metabolic processes to precipitate cementitious calcium carbonate.The reactive transport of biochemical species in the soil mass initiates the precipitation of biocement during the MICP process.The precipitated biocement alters the hydro-mechanical performance of the soil mass.Usually,the flow,deformation,and transport phenomena regulate the biocementation technique via coupled bio-chemo-hydro-mechanical(BCHM)processes.Among all,one crucial phenomenon controlling the precipitation mechanism is the encapsulation of biomass by calcium carbonate.Biomass encapsulation can potentially reduce the biochemical reaction rate and decelerate biocementation.Laboratory examination of the encapsulation process demands a thorough analysis of associated coupled effects.Despite this,a numerical model can assist in capturing the coupled processes influencing encapsulation during the MICP treatment.However,most numerical models did not consider biochemical reaction rate kinetics accounting for the influence of bacterial encapsulation.Given this,the current study developed a coupled BCHM model to evaluate the effect of encapsulation on the precipitated calcite content using a micro-scale semiempirical relationship.Firstly,the developed BCHM model was verified and validated using numerical and experimental observations of soil column tests.Later,the encapsulation phenomenon was investigated in the soil columns of variable maximum calcite crystal sizes.The results depict altered reaction rates due to the encapsulation phenomenon and an observable change in the precipitated calcite content for each maximum crystal size.Furthermore,the permeability and deformation of the soil mass were affected by the simultaneous precipitation of calcium carbonate.Overall,the present study comprehended the influence of the encapsulation of bacteria on cement morphology-induced permeability,biocement-induced stresses and displacements.展开更多
Microbially or enzyme induced carbonate precipitation has emerged to be a new type of soil improvement method.However,it appears that the biocementation process is affected by many factors and a common understanding o...Microbially or enzyme induced carbonate precipitation has emerged to be a new type of soil improvement method.However,it appears that the biocementation process is affected by many factors and a common understanding on the control factors on the biocement effect has not been reached.This paper attempts to identify the main factors that controlling the MICP or EICP effect through an in-depth discussion on the fundamentals of biocementation process.Similar to other cemented granular materials,biocemented soil is a structural soil composite consisting of soil skeleton and biocement force chain or biocement network.The strength and stiffness of the biocemented soil is controlled by the reinforcement effect of the biocement network on the soil skeleton or the interplay of the soil skeleton and precipitates.The contribution of the strength by soil skeleton is affected by the soil types and soil properties,while the contribution of the precipitates is through the distribution of the biocement network and the properties of the precipitates.展开更多
Biocementation is an emerging field within geotechnical engineering that focuses on harnessing microbiological activity to enhance the mechanical properties and behavior of rocks. It often relies on microbial-induced ...Biocementation is an emerging field within geotechnical engineering that focuses on harnessing microbiological activity to enhance the mechanical properties and behavior of rocks. It often relies on microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP) which utilizes biomineralization by promoting the generation of calcium carbonate (CaCO3) within the pores of geomaterials (rock and soil). However, there is still a lack of knowledge about the effect of porosity and bedding on biocementation in rocks from a mechanistic view. This experimental study investigated the impact of porosity and bedding orientations on the mechanical response of rocks due to biocementations, using two distinct biocementation strategies (MICP and EICP) and characteristically low porosity but interbedded rocks (shale) and more porous but non-bedded (dolostone) rocks. We first conducted biocementation treatments (MICP and EICP) of rock samples over a distinct period and temperature. Subsequently, the rock strength (uniaxial compressive strength, UCS) was measured. Finally, we analyzed the pre- and post-treatment changes in the rock samples to better understand the effect of MICP and EICP biocementations on the mechanical response of the rock samples. The results indicate that biocementations in dolostones can improve the rock mechanical integrity (EICP: +58% UCS;MICP: +25% UCS). In shales, biocementations can either slightly improve (EICP: +1% UCS) or weaken the rock mechanical integrity (MICP: -39% UCS). Further, results suggest that the major controlling mechanisms of biogeomechanical alterations due to MICP and EICP in rocks can be attributed to the inherent porosity, biocementation type, and bedding orientations, and in few cases the mechanisms can be swelling, osmotic suction, or pore pressurization. The findings in this study provide novel insights into the mechanical responses of rocks due to MICP and EICP biocementations.展开更多
A close relationship exists between the pore network structure of microbial solidified soil and its macroscopic mechanical properties.The microbial solidified engineering residue and sand were scanned by computed tomo...A close relationship exists between the pore network structure of microbial solidified soil and its macroscopic mechanical properties.The microbial solidified engineering residue and sand were scanned by computed tomography(CT),and a three-dimensional model of the sample was established by digital image processing.A spatial pore network ball-stick model of the representative elementary volume(REV)was established,and the REV parameters of the sample were calculated.The pore radius,throat radius,pore coordination number,and throat length were normally distributed.The soil particle size was larger after solidification.The calcium carbonate content of the microbial solidified engineering residue’s consolidated layer decreased with the soil depth,the porosity increased,the pore and throat network developed,and the ultimate structure was relatively stable.The calcium carbonate content of the microbial solidified sand’s consolidated layer decreased and increased with the soil depth.The content reached the maximum,the hardness of the consolidated layer was the highest,and the development of the pore and throat network was optimum at a depth of 10–15 mm.展开更多
Bacterial suspension is an essential component of microbially induced carbonate precipitation(MICP)-based biocement and a large-scale production is required for field applications.In this study,a new bacterial concent...Bacterial suspension is an essential component of microbially induced carbonate precipitation(MICP)-based biocement and a large-scale production is required for field applications.In this study,a new bacterial concentration method is proposed to enable high concentration bacterial suspension to be produced to facilitate field work.By adding low concentration calcium to bacterial suspension,flocs are formed and bacterial cells are adsorbed on the flocs to achieve bacterial concentration.Compared to the traditional bacterial concentration method using centrifugation and freezing-drying method,the proposed method can concentrate a large volume of bacterial suspension without using special equipment.The feasibility of this method is verified by bacterial concentration tests,solution tests and sand column treatment tests.The results of both the solution test and the sand column treatment test show that the bacterial suspension concentrated by the proposed method can be effectively used for soil biocementation.There is a threshold calcium concentration that allows a complete bacterial concentration for the proposed method,and this threshold calcium concentration tends to increase linearly with the optical density of the cell suspension at a wavelength of 600 nm(OD_(600)).展开更多
Loose tailings are susceptible to static liquefaction during which they lose a substantial amount of their strength.This study examines a sustainable technique known as Microbially-Induced Calcite Precipitation(MICP)t...Loose tailings are susceptible to static liquefaction during which they lose a substantial amount of their strength.This study examines a sustainable technique known as Microbially-Induced Calcite Precipitation(MICP)to improve the static liquefaction resistance of gold mine silty sand tailings.These materials were enriched with Sporosarcina pasteurii,consolidated in a direct simple shearing apparatus,and subjected to several injections of a cementation solution.Calcified tailings were then sheared under constant-volume and constant vertical stress conditions to evaluate their undrained and drained shearing behaviors.Results showed that bio-mineralization can prevent the occurrence of static liquefaction in tailings by reducing their contraction tendency.This is demonstrated by the strong strain-hardening behaviors of the treated tailings specimens compared to the strain-softening and undrained strength loss in specimens of the untreated tailings.Substantial increases in the tailings undrained and drained shear strengths(by up to 30-50 kPa),improvements(by up to 5 MPa)in their tangent moduli,and more than 5°rise in their friction angles are observed in the direct simple shear tests following MICP-treatment.The critical state line of tailings is also found to be steeper and shifted to denser void ratios following MICP treatment.These changes reduce liquefaction susceptibility of tailings and enhance their resistance against static liquefaction.Post-treatment acid dissolution further indicates that CaCO_(3)contents of about 4%to 11%precipitated in the treated specimens.This amount decreases with increasing specimens void ratio.Changes in the microstructural fabric of the cemented tailings particles are also characterized using scanning electron microscopic(SEM)images and X-ray diffraction(XRD)analyses.展开更多
Because of the high cost of cultivating urease-producing bacteria(UPB),this paper proposes soybean-urease-induced carbonate precipitation(SUICP)as a novel biocement for treatment of nickel contaminants and cementation...Because of the high cost of cultivating urease-producing bacteria(UPB),this paper proposes soybean-urease-induced carbonate precipitation(SUICP)as a novel biocement for treatment of nickel contaminants and cementation of sandy soil.We found the optimal soaking time and soybean-powder content to be 30 min and 130 g/L,respectively,based on a standard of 5 U of urease activity.The most efficient removal of nickel ions is obtained with an ideal mass ratio of urea to nickel ions to soybean-powder filtrate(SPF)of 1:2.4:20.The removal efficiency of nickel ions can reach 89.42%when treating 1 L of nickel-ion solution(1200 mg/L with the optimal mass ratio).In incinerated bottom ash(IBA),the removal efficiency of nickel ions is 99.33%with the optimal mass ratio.In biocemented sandy soil,the average unconfined compressive strength(UCS)of sand blocks cemented with soybean urease-based biocement can reach 118.89 kPa when the cementation level is 3.Currently,the average content of CaCO_(3)in sand blocks is 2.52%.As a result,the SUICP process can be applied to remove heavy metal ions in wastewater or solid waste and improve the mechanical properties of soft soil foundations.展开更多
Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate p...Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate precipitation(SICP)on reducing wind erosion risk of sandy soil.Field tests were carried out in Ulan Buh Desert,Ningxia Hui Autonomous Region,China.Results showed that the SICP method could significantly enhance the surface strength and wind erosion resistance of the topsoil.The optimal cementation solution(urea-CaCl2)concentration and spraying volume,according to experiments conducted on sandy land,were 0.2 mol/L and 4 L/m^2,respectively.Under this condition,the CaCO3 content was approximately 0.45%,the surface strength of sandy soil could reach 306.2 kPa,and the depth of wind erosion was approximately zero,after 30 d completion of SICP treatment.Soil surface strength declined with the increase of time,and long-term sand fixation effects of SICP treatment varied depending on topography.Whereas wind erosion in the top area of the windward slope was remarkable,sandy soils on the bottom area of the windward slope still maintained a relatively high level of surface strength and a low degree of wind erosion 12 month after SICP treatment.Scanning electron microscopy(SEM)tests with energy dispersive X-ray(EDX)confirmed the precipitation of CaCO3 and its bridge effect.These findings suggested that the SICP method is a promising candidate to protect sandy soil from wind erosion in desert areas.展开更多
Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bio...Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bioclogging.This rate of modification mainly depends on the amount,and nature of biomineral pre-cipitated and it is influenced by various environmental,chemical,and microbial factors.Given this,the present study aims to investigate the effect of biochemical conditions such as concentration of biomass and chemical reagents on the amount and nature of biomineral and its impact on the strength and permeability of biomodified sand.For this,the two microbes i.e.,Sporosarcina pasteuri and isolated Proteus species at three different initial concentrations and chemical reagents by varying 0.1-1 molar of urea and calcium were considered.The amount and microstructural behavior of biomineral in different biochemical conditions concluded that the governing mechanism differs for both biocementation and bioclogging under identical MICP treatment.The strength enhancement or biocementation is dependent on the size of the biomineral precipitated whereas the reduction in permeability or bioclogging is mainly dominated by the amount of biomineral.The optimum value of biochemical conditions i.e.,1o°cells/ml of biomass and 0.25 M con-centration of cementation reagents was chosen to further evaluate the effect of equal MICP treatment on the biocementation and bioclogging of sands having different grain sizes.The study infers that not the absolute size of the biomineral but the relative size of soil grain and biomineral influence the linkage between the soil particles and hence affect the strength of biomodified soil.展开更多
Biocementation-based soil improvement is an emerging ground treatment method in geotechnical engineering that has garnered extensive attention over the past two decades.One of the challenges associated with this metho...Biocementation-based soil improvement is an emerging ground treatment method in geotechnical engineering that has garnered extensive attention over the past two decades.One of the challenges associated with this method revolves around the uniformity of biocementation,a crucial factor closely tied to bio-grouting technology.The traditional biotreatment methods,the two-phase method and the one-phase method,suffer from the issue of non-uniform biocementation.Consequently,in recent years,various improved grouting technologies have been proposed to address this concern by aiding bacterial adsorption and controlling carbonate precipitation.This paper reviews the mechanisms and grouting processes employed in these enhanced bio-grouting technologies.Additionally,the challenges of implementing these grouting technologies in real-world applications are also thoroughly discussed.展开更多
Compromised integrity of cementitious materials can lead to potential geo-hazards such as detrimental fluid flow to the wellbore(borehole),potential leakage of underground stored fluids,contamination of water aquifers...Compromised integrity of cementitious materials can lead to potential geo-hazards such as detrimental fluid flow to the wellbore(borehole),potential leakage of underground stored fluids,contamination of water aquifers,and other issues that could impact environmental sustainability during underground construction operations.The mechanical integrity of wellbore cementitious materials is critical to prevent wellbore failure and leakages,and thus,it is imperative to understand and predict the integrity of oilwell cement(OWC)and microbial-induced calcite precipitation(MICP)to maintain wellbore integrity and ensure zonal isolation at depth.Here,we investigated the mechanical integrity of two cementitious materials(MICP and OWC),and assessed their potential for plugging leakages around the wellbore.Further,we applied Machine Learning(ML)models to upscale and predict near-wellbore mechanical integrity at macro-scale by adopting two ML algorithms,Artificial Neural Network(ANN)and Random Forest(RF),using 100 datasets(containing 100 observations).Fractured portions of rock specimens were treated with MICP and OWC,respectively,and their resultant mechanical integrity(unconfined compressive strength,UCS;fracture toughness,K_(s))were evaluated using experimental mechanical tests and ML models.The experimental results showed that although OWC(average UCS=97 MPa,K_(s)=4.3 MPa·√m)has higher mechanical integrity over MICP(average UCS=86 MPa,K_(s)=3.6 MPa·√m),the MICP showed an edge over OWC in sealing microfractures and micro-leakage pathways.Also,the OWC can provide a greater near-wellbore seal than MICP for casing-cement or cement-formation delamination with relatively greater mechanical integrity.The results show that the degree of correlation between the mechanical integrity obtained from lab tests and the ML predictions is high.The best ML algorithm to predict the macro-scale mechanical integrity of a MICP-cemented specimen is the RF model(R^(2)for UCS=0.9738 and K_(s)=0.9988;MAE for UCS=1.04 MPa and K_(s)=0.02 MPa·√m).Similarly,for OWC-cemented specimen,the best ML algorithm to predict their macro-scale mechanical integrity is the RF model(R^(2)for UCS=0.9984 and K_(s)=0.9996;MAE for UCS=0.5 MPa and K_(s)=0.01 MPa·√m).This study provides insights into the potential of MICP and OWC as near-wellbore ce-mentitious materials and the applicability of ML model for evaluating and predicting the mechanical integrity of cementitious materials used in near-wellbore to achieve efficient geo-hazard mitigation and environmental protection in engineering and underground operations.展开更多
Reasonable control of rainwater infiltration rate can ensure that soil slope will not fail due to rapid infiltration of rainwater in heavy rainfall,and at the same time,more rainwater can be infiltrated in light rainf...Reasonable control of rainwater infiltration rate can ensure that soil slope will not fail due to rapid infiltration of rainwater in heavy rainfall,and at the same time,more rainwater can be infiltrated in light rainfall to meet the water demand of animals and plants.In this study,based on microbial-induced calcium carbonate precipitation(MICP)technique,a controllable bio-method for rainfall infiltration of soil slope was proposed.To have a comprehensive understanding the relationship among the rainwater infiltration control capacity,biocement treated soil permeability,slope angle and rainfall intensity,a series of physical modelling experiments of rainfall diversion on slopes with three types of soils and three slope angles were carried out in the presence of various rainfall intensities.Experimental results indicated that the proposed bio-method had the ability of controlling rainwater infiltration in term of varying rounds of biocement spraying treatment.In general,it was found that the rainwater infiltration decreases with the increase in slope angle and rainfall intensity.In the worst case of smallest slope angle(15°)and lightest rainfall intensity(n=50 mm/h),more than 82.6%,92.2%and 84.4%of rainwater were prevented from infiltration into the MICP treated natural sand,fine sand and medium sand,respectively,while the untreated soils were not able to prevent the rainwater infiltration at all.The corre-sponding maximum local uniaxial compressive strength for the MICP treated natural sand,fine sand and medium sand,respectively,were found to be 2.3 MPa,2.0 MPa,2.6 MPa,whereas the flexural stresses were 0.46 MPa,0.33 MPa,0.67 MPa,which could resist rainfall droplet impact force.Overall,the proposed bio-method showed good rainwater infiltration control capacity and high bearing strength against the impact of heavy rainfalls,suggesting a good potential to mitigate the rainfall-induced landslides.展开更多
Microbially induced carbonate precipitation(MICP)is a new technology having the potential to induce soil stabilization and provide a green and sustainable comprehensive solution to some geotechnical engineering proble...Microbially induced carbonate precipitation(MICP)is a new technology having the potential to induce soil stabilization and provide a green and sustainable comprehensive solution to some geotechnical engineering problems in the environment.The present article is dedicated to present a critical review of this technology and discuss its mechanisms of action and the key factors influencing its performance.The global experiences and national participation from Egypt are demonstrated,in addition to attempts for real life applications.This review provides an insight into the practical steps taken to mitigate some of the current limitations of MICP application and the identified gaps in analogous studies.It was concluded that integrating MICP with existing technologies would favor both engineering needs and market requirements.In addition,providing effective solutions to MICP limitations would highlight this technology as an eco-friendly and cost-effective option to several engineering obstacles.Finally,recommendations focused on encouraging global collaboration for knowledge transfer about this technology among different countries,as well as positive financial support from industrial entities to aid in the progress of scientific research and achieving large-scale applications in the near future,are provided.展开更多
Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have b...Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have been developed in recent years based on this approach.A proper understanding of the various approaches and the performances of different methods can help researchers and engineers to develop the most appropriate geotechnical solutions.At present,most of the methods can be categorized into three major types,biocementation,bioclogging,and biogas desaturation.Similarities and differences of different approaches and their potential applications are reviewed.Factors affecting the different processes are also discussed.Examples of up-scaled model tests and pilot trials are presented to show the emerging applications.The challenges and problems of biogeotechnology are also discussed.展开更多
基金supported by the National Natural Science Foundation of China(No.51978103,No.52308340,No.52408355)the Postdoctoral Fellowship Program of CPSF(No.BX20240450)Chongqing Talent Innovation and Entrepreneurship Demonstration Team Project(No.cstc2024ycjh-bgzxm0012).
文摘The biocemented coral sand pile composite foundation represents an innovative foundation improvement technology,utilizing Microbially Induced Carbonate Precipitation(MICP)to consolidate a specific volume of coral sand within the foundation into piles with defined strength,thereby enabling them to collaboratively bear external loads with the surrounding unconsolidated coral sand.In this study,a series of shaking table model tests were conducted to explore the dynamic response of the biocemented coral sand pile composite foundation under varying seismic wave types and peak accelerations.The surface macroscopic phenomena,excess pore water pressure ratio,acceleration response,and vertical settlement were measured and analysed in detail.Test results show that seismic wave types play a decisive role in the macroscopic surface phenomena and the response of the excess pore water pressure ratio.The cumulative settlement of the upper structure under the action of Taft waves was about 1.5 times that of El Centro waves and Kobe waves.The most pronounced liquefaction phenomena were recorded under the Taft wave,followed by the El Centro wave,and subsequently the Kobe wave.An observed positive correlation was established between the liquefaction phenomenon and the Aristotelian in-tensity of the seismic waves.However,variations in seismic wave types exerted minimal influence on the ac-celeration amplification factor of the coral sand foundation.Analysis of the acceleration amplification factor revealed a triphasic pattern-initially increasing,subsequently decreasing,and finally increasing again-as burial depth increased,in relation to the peak value of the input acceleration.This study confirms that the biocemented coral sand pile composite foundation can effectively enhance the liquefaction resistance of coral sand foundations..
文摘It is difficult to collect and characterise well-preserved samples of weakly-cemented granular rocks as conventional sampling techniques often result in destruction of the cementation.An alternative approach is to prepare synthetic geomaterials to match required specifications.This paper introduces microbially induced carbonate precipitation(MICP)as a method to reliably deliver artificiallycemented specimens with customised properties,closely resembling those of soft carbonate sandstones.The specimens are generated from materials with two highly different particle size distributions(PSDs)to access a range of achievable combinations of strengths and porosities.The MICP parameters are kept constant across all samples to obtain similar calcium carbonate characteristics(size of individual crystals,type,etc.),while injected volume is varied to achieve different cementation levels.Although uniform cementation of very coarse sands has been considered very difficult to achieve,the results show that both the fine and coarse sand specimens present high degrees of uniformity and a good degree of repeatability.The unconfined compressive strengths(UCSs)(less than 3000 kPa)and porosities(0.25e0.4)of the artificial specimens fall in the same range of values reported for natural rocks.The strength gainwas greater in the fine sand than that in the coarse sand,as the void size in the latter was significantly larger compared to the calcium carbonate crystals’size,resulting in precipitation on less effective locations,away from contacts between particles.The strengths and porosities obtained for the two sands in this work fall within ranges reported in the literature for natural soft rocks,demonstrating theMICP technique is able to achieve realistic properties and may be used to produce a full range of properties by varying the grain sizes,and possibly the width of PSD.
基金FCT I.P,for the funding through CALCITE Project(ref.PTDC/ECI-EGC/1086/2021).
文摘This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method.It is developed in the context of biocementation as soil improvement technique,which is used in Civil Engineering applications to produce calcium carbonate through bacterial or enzymatic activity,replacing the use of other binder materials such as cement or resins,and therefore reducing carbon footprint.The microdevice was used to measure urease activity in the soil interstitial fluid,to investigate if bacterial activity could be affected by the presence of the particles and tortuosity from pore geometry.Such analysis is important to understand biocementation mechanism inside the soil and helps to improve the design of such treatment solutions.The device is basically a squared reservoir printed in polypropylene using a 3D printing machine,incorporating stainless steel electrodes in its base.The electrical resistivity was computed adopting Wenner method,by connecting 4 PCB electrodes to a signal generator and an oscilloscope for measuring the voltage when a AC current of 1 mA was applied.Both square and sinusoidal waves with 5 kHz frequency were selected among other frequencies.The measurements were adjusted during the calibration of the microdevice,done using standard salt solutions with known electrical conductivity measured using an electrical conductivity probe.For the bacterial activity measurements,the bacterial and urea solutions were added to a uniform-graded size quarzitic sand(average diameter 0.3 mm)placed inside the microdevice and covering completely the electrodes.Bacterial activity was not affected by the presence of the sand,which confirms that this treatment is effective for this type of soils.
基金We acknowledge the funding support from the National Natural Science Foundation of China(Grant Nos.51922024 and 52078085)Chongqing Talents Program,China(Grant No.cstc2021ycjhbgzxm0051).
文摘Biomineralization through microbial process has attracted great attention in the field of geotechnical engineering due to its ability to bind granular materials,clog pores,and seal fractures.Although minerals formed by biomineralization are generally the same as that by mineralization,their mechanical behaviors show a significant discrepancy.This study aims to figure out the differences between biomineralization and mineralization processes by visualizing and tracking the formation of minerals using microfluidics.Both biomineralization and mineralization processes occurred in the Y-shaped sandcontaining microchip that mimics the underground sand layers.Images from different areas in the reaction microchannel of microchips were captured to directly compare the distribution of minerals.Crystal size and numbers from different reaction times were measured to quantify the differences between biomineralization and mineralization processes in terms of crystal kinetics.Results showed that the crystals were precipitated in a faster and more uncontrollable manner in the mineralization process than that in the biomineralization process,given that those two processes presented similar precipitation stages.In addition,a more heterogeneous distribution of crystals was observed during the biomineralization process.The precipitation behaviors were further explained by the classical nucleation crystal growth theory.The present microfluidic tests could advance the understanding of biomineralization and provide new insight into the optimization of biocementation technology.
基金the funding support from the Ministry of Education,Government of India,under the Prime Minister Research Fellowship programme(Grant Nos.SB21221901CEPMRF008347 and SB22230217CEPMRF008347).
文摘Geomaterials with inferior hydraulic and strength characteristics often need improvement to enhance their engineering behaviors.Traditional ground improvement techniques require enormous mechanical effort or synthetic chemicals.Sustainable stabilization technique such as microbially induced calcite precipitation(MICP)utilizes bacterial metabolic processes to precipitate cementitious calcium carbonate.The reactive transport of biochemical species in the soil mass initiates the precipitation of biocement during the MICP process.The precipitated biocement alters the hydro-mechanical performance of the soil mass.Usually,the flow,deformation,and transport phenomena regulate the biocementation technique via coupled bio-chemo-hydro-mechanical(BCHM)processes.Among all,one crucial phenomenon controlling the precipitation mechanism is the encapsulation of biomass by calcium carbonate.Biomass encapsulation can potentially reduce the biochemical reaction rate and decelerate biocementation.Laboratory examination of the encapsulation process demands a thorough analysis of associated coupled effects.Despite this,a numerical model can assist in capturing the coupled processes influencing encapsulation during the MICP treatment.However,most numerical models did not consider biochemical reaction rate kinetics accounting for the influence of bacterial encapsulation.Given this,the current study developed a coupled BCHM model to evaluate the effect of encapsulation on the precipitated calcite content using a micro-scale semiempirical relationship.Firstly,the developed BCHM model was verified and validated using numerical and experimental observations of soil column tests.Later,the encapsulation phenomenon was investigated in the soil columns of variable maximum calcite crystal sizes.The results depict altered reaction rates due to the encapsulation phenomenon and an observable change in the precipitated calcite content for each maximum crystal size.Furthermore,the permeability and deformation of the soil mass were affected by the simultaneous precipitation of calcium carbonate.Overall,the present study comprehended the influence of the encapsulation of bacteria on cement morphology-induced permeability,biocement-induced stresses and displacements.
基金support by the National Natural Science Foundation of China(NSFC)(Grant Nos.52178319,52108307,51708243)the Natural Science Foundation of Fujian Province,China(Grant Nos.2022J05020,2022J05127).
文摘Microbially or enzyme induced carbonate precipitation has emerged to be a new type of soil improvement method.However,it appears that the biocementation process is affected by many factors and a common understanding on the control factors on the biocement effect has not been reached.This paper attempts to identify the main factors that controlling the MICP or EICP effect through an in-depth discussion on the fundamentals of biocementation process.Similar to other cemented granular materials,biocemented soil is a structural soil composite consisting of soil skeleton and biocement force chain or biocement network.The strength and stiffness of the biocemented soil is controlled by the reinforcement effect of the biocement network on the soil skeleton or the interplay of the soil skeleton and precipitates.The contribution of the strength by soil skeleton is affected by the soil types and soil properties,while the contribution of the precipitates is through the distribution of the biocement network and the properties of the precipitates.
文摘Biocementation is an emerging field within geotechnical engineering that focuses on harnessing microbiological activity to enhance the mechanical properties and behavior of rocks. It often relies on microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP) which utilizes biomineralization by promoting the generation of calcium carbonate (CaCO3) within the pores of geomaterials (rock and soil). However, there is still a lack of knowledge about the effect of porosity and bedding on biocementation in rocks from a mechanistic view. This experimental study investigated the impact of porosity and bedding orientations on the mechanical response of rocks due to biocementations, using two distinct biocementation strategies (MICP and EICP) and characteristically low porosity but interbedded rocks (shale) and more porous but non-bedded (dolostone) rocks. We first conducted biocementation treatments (MICP and EICP) of rock samples over a distinct period and temperature. Subsequently, the rock strength (uniaxial compressive strength, UCS) was measured. Finally, we analyzed the pre- and post-treatment changes in the rock samples to better understand the effect of MICP and EICP biocementations on the mechanical response of the rock samples. The results indicate that biocementations in dolostones can improve the rock mechanical integrity (EICP: +58% UCS;MICP: +25% UCS). In shales, biocementations can either slightly improve (EICP: +1% UCS) or weaken the rock mechanical integrity (MICP: -39% UCS). Further, results suggest that the major controlling mechanisms of biogeomechanical alterations due to MICP and EICP in rocks can be attributed to the inherent porosity, biocementation type, and bedding orientations, and in few cases the mechanisms can be swelling, osmotic suction, or pore pressurization. The findings in this study provide novel insights into the mechanical responses of rocks due to MICP and EICP biocementations.
基金supported by the National Natural Science Foundation of China(51580166).
文摘A close relationship exists between the pore network structure of microbial solidified soil and its macroscopic mechanical properties.The microbial solidified engineering residue and sand were scanned by computed tomography(CT),and a three-dimensional model of the sample was established by digital image processing.A spatial pore network ball-stick model of the representative elementary volume(REV)was established,and the REV parameters of the sample were calculated.The pore radius,throat radius,pore coordination number,and throat length were normally distributed.The soil particle size was larger after solidification.The calcium carbonate content of the microbial solidified engineering residue’s consolidated layer decreased with the soil depth,the porosity increased,the pore and throat network developed,and the ultimate structure was relatively stable.The calcium carbonate content of the microbial solidified sand’s consolidated layer decreased and increased with the soil depth.The content reached the maximum,the hardness of the consolidated layer was the highest,and the development of the pore and throat network was optimum at a depth of 10–15 mm.
基金supports by the National Natural Science Foundation of China(Grant Nos.52108307 and 52178319)the National Natural Science Foundation of Fujian Province,China(Grant No.2022J05020).
文摘Bacterial suspension is an essential component of microbially induced carbonate precipitation(MICP)-based biocement and a large-scale production is required for field applications.In this study,a new bacterial concentration method is proposed to enable high concentration bacterial suspension to be produced to facilitate field work.By adding low concentration calcium to bacterial suspension,flocs are formed and bacterial cells are adsorbed on the flocs to achieve bacterial concentration.Compared to the traditional bacterial concentration method using centrifugation and freezing-drying method,the proposed method can concentrate a large volume of bacterial suspension without using special equipment.The feasibility of this method is verified by bacterial concentration tests,solution tests and sand column treatment tests.The results of both the solution test and the sand column treatment test show that the bacterial suspension concentrated by the proposed method can be effectively used for soil biocementation.There is a threshold calcium concentration that allows a complete bacterial concentration for the proposed method,and this threshold calcium concentration tends to increase linearly with the optical density of the cell suspension at a wavelength of 600 nm(OD_(600)).
基金funded through an"Early Researcher Award"from the Ontario Ministry of Research,Innovation and Science.
文摘Loose tailings are susceptible to static liquefaction during which they lose a substantial amount of their strength.This study examines a sustainable technique known as Microbially-Induced Calcite Precipitation(MICP)to improve the static liquefaction resistance of gold mine silty sand tailings.These materials were enriched with Sporosarcina pasteurii,consolidated in a direct simple shearing apparatus,and subjected to several injections of a cementation solution.Calcified tailings were then sheared under constant-volume and constant vertical stress conditions to evaluate their undrained and drained shearing behaviors.Results showed that bio-mineralization can prevent the occurrence of static liquefaction in tailings by reducing their contraction tendency.This is demonstrated by the strong strain-hardening behaviors of the treated tailings specimens compared to the strain-softening and undrained strength loss in specimens of the untreated tailings.Substantial increases in the tailings undrained and drained shear strengths(by up to 30-50 kPa),improvements(by up to 5 MPa)in their tangent moduli,and more than 5°rise in their friction angles are observed in the direct simple shear tests following MICP-treatment.The critical state line of tailings is also found to be steeper and shifted to denser void ratios following MICP treatment.These changes reduce liquefaction susceptibility of tailings and enhance their resistance against static liquefaction.Post-treatment acid dissolution further indicates that CaCO_(3)contents of about 4%to 11%precipitated in the treated specimens.This amount decreases with increasing specimens void ratio.Changes in the microstructural fabric of the cemented tailings particles are also characterized using scanning electron microscopic(SEM)images and X-ray diffraction(XRD)analyses.
基金supported by the Opening Funds of Jiangsu Key Laboratory of Construction Materials(No.CM2018-02)the Key Project of Natural Science Foundation of Zhejiang Province,China(No.LZ22E080003)the General Project of Natural Science Foundation of Zhejiang Province,China(No.LY20E080002).
文摘Because of the high cost of cultivating urease-producing bacteria(UPB),this paper proposes soybean-urease-induced carbonate precipitation(SUICP)as a novel biocement for treatment of nickel contaminants and cementation of sandy soil.We found the optimal soaking time and soybean-powder content to be 30 min and 130 g/L,respectively,based on a standard of 5 U of urease activity.The most efficient removal of nickel ions is obtained with an ideal mass ratio of urea to nickel ions to soybean-powder filtrate(SPF)of 1:2.4:20.The removal efficiency of nickel ions can reach 89.42%when treating 1 L of nickel-ion solution(1200 mg/L with the optimal mass ratio).In incinerated bottom ash(IBA),the removal efficiency of nickel ions is 99.33%with the optimal mass ratio.In biocemented sandy soil,the average unconfined compressive strength(UCS)of sand blocks cemented with soybean urease-based biocement can reach 118.89 kPa when the cementation level is 3.Currently,the average content of CaCO_(3)in sand blocks is 2.52%.As a result,the SUICP process can be applied to remove heavy metal ions in wastewater or solid waste and improve the mechanical properties of soft soil foundations.
基金Projects(51978244,51979088,51608169)supported by the National Natural Science Foundation of China。
文摘Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate precipitation(SICP)on reducing wind erosion risk of sandy soil.Field tests were carried out in Ulan Buh Desert,Ningxia Hui Autonomous Region,China.Results showed that the SICP method could significantly enhance the surface strength and wind erosion resistance of the topsoil.The optimal cementation solution(urea-CaCl2)concentration and spraying volume,according to experiments conducted on sandy land,were 0.2 mol/L and 4 L/m^2,respectively.Under this condition,the CaCO3 content was approximately 0.45%,the surface strength of sandy soil could reach 306.2 kPa,and the depth of wind erosion was approximately zero,after 30 d completion of SICP treatment.Soil surface strength declined with the increase of time,and long-term sand fixation effects of SICP treatment varied depending on topography.Whereas wind erosion in the top area of the windward slope was remarkable,sandy soils on the bottom area of the windward slope still maintained a relatively high level of surface strength and a low degree of wind erosion 12 month after SICP treatment.Scanning electron microscopy(SEM)tests with energy dispersive X-ray(EDX)confirmed the precipitation of CaCO3 and its bridge effect.These findings suggested that the SICP method is a promising candidate to protect sandy soil from wind erosion in desert areas.
文摘Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bioclogging.This rate of modification mainly depends on the amount,and nature of biomineral pre-cipitated and it is influenced by various environmental,chemical,and microbial factors.Given this,the present study aims to investigate the effect of biochemical conditions such as concentration of biomass and chemical reagents on the amount and nature of biomineral and its impact on the strength and permeability of biomodified sand.For this,the two microbes i.e.,Sporosarcina pasteuri and isolated Proteus species at three different initial concentrations and chemical reagents by varying 0.1-1 molar of urea and calcium were considered.The amount and microstructural behavior of biomineral in different biochemical conditions concluded that the governing mechanism differs for both biocementation and bioclogging under identical MICP treatment.The strength enhancement or biocementation is dependent on the size of the biomineral precipitated whereas the reduction in permeability or bioclogging is mainly dominated by the amount of biomineral.The optimum value of biochemical conditions i.e.,1o°cells/ml of biomass and 0.25 M con-centration of cementation reagents was chosen to further evaluate the effect of equal MICP treatment on the biocementation and bioclogging of sands having different grain sizes.The study infers that not the absolute size of the biomineral but the relative size of soil grain and biomineral influence the linkage between the soil particles and hence affect the strength of biomodified soil.
基金support by the National Natural Science Foundation of China(NSFC)(Grant Nos.52178319,52108307,52078236,51878313,51708243)the Natural Science Foundation of Fujian Province,China(Grant Nos.2022J05020,2022J05127).
文摘Biocementation-based soil improvement is an emerging ground treatment method in geotechnical engineering that has garnered extensive attention over the past two decades.One of the challenges associated with this method revolves around the uniformity of biocementation,a crucial factor closely tied to bio-grouting technology.The traditional biotreatment methods,the two-phase method and the one-phase method,suffer from the issue of non-uniform biocementation.Consequently,in recent years,various improved grouting technologies have been proposed to address this concern by aiding bacterial adsorption and controlling carbonate precipitation.This paper reviews the mechanisms and grouting processes employed in these enhanced bio-grouting technologies.Additionally,the challenges of implementing these grouting technologies in real-world applications are also thoroughly discussed.
文摘Compromised integrity of cementitious materials can lead to potential geo-hazards such as detrimental fluid flow to the wellbore(borehole),potential leakage of underground stored fluids,contamination of water aquifers,and other issues that could impact environmental sustainability during underground construction operations.The mechanical integrity of wellbore cementitious materials is critical to prevent wellbore failure and leakages,and thus,it is imperative to understand and predict the integrity of oilwell cement(OWC)and microbial-induced calcite precipitation(MICP)to maintain wellbore integrity and ensure zonal isolation at depth.Here,we investigated the mechanical integrity of two cementitious materials(MICP and OWC),and assessed their potential for plugging leakages around the wellbore.Further,we applied Machine Learning(ML)models to upscale and predict near-wellbore mechanical integrity at macro-scale by adopting two ML algorithms,Artificial Neural Network(ANN)and Random Forest(RF),using 100 datasets(containing 100 observations).Fractured portions of rock specimens were treated with MICP and OWC,respectively,and their resultant mechanical integrity(unconfined compressive strength,UCS;fracture toughness,K_(s))were evaluated using experimental mechanical tests and ML models.The experimental results showed that although OWC(average UCS=97 MPa,K_(s)=4.3 MPa·√m)has higher mechanical integrity over MICP(average UCS=86 MPa,K_(s)=3.6 MPa·√m),the MICP showed an edge over OWC in sealing microfractures and micro-leakage pathways.Also,the OWC can provide a greater near-wellbore seal than MICP for casing-cement or cement-formation delamination with relatively greater mechanical integrity.The results show that the degree of correlation between the mechanical integrity obtained from lab tests and the ML predictions is high.The best ML algorithm to predict the macro-scale mechanical integrity of a MICP-cemented specimen is the RF model(R^(2)for UCS=0.9738 and K_(s)=0.9988;MAE for UCS=1.04 MPa and K_(s)=0.02 MPa·√m).Similarly,for OWC-cemented specimen,the best ML algorithm to predict their macro-scale mechanical integrity is the RF model(R^(2)for UCS=0.9984 and K_(s)=0.9996;MAE for UCS=0.5 MPa and K_(s)=0.01 MPa·√m).This study provides insights into the potential of MICP and OWC as near-wellbore ce-mentitious materials and the applicability of ML model for evaluating and predicting the mechanical integrity of cementitious materials used in near-wellbore to achieve efficient geo-hazard mitigation and environmental protection in engineering and underground operations.
基金supports from the Ministry of National Development,Singapore(No.SUL2013-1)the National Research Foundation of Singapore(L2NICCFP2-2015-1)are gratefully acknowledged.
文摘Reasonable control of rainwater infiltration rate can ensure that soil slope will not fail due to rapid infiltration of rainwater in heavy rainfall,and at the same time,more rainwater can be infiltrated in light rainfall to meet the water demand of animals and plants.In this study,based on microbial-induced calcium carbonate precipitation(MICP)technique,a controllable bio-method for rainfall infiltration of soil slope was proposed.To have a comprehensive understanding the relationship among the rainwater infiltration control capacity,biocement treated soil permeability,slope angle and rainfall intensity,a series of physical modelling experiments of rainfall diversion on slopes with three types of soils and three slope angles were carried out in the presence of various rainfall intensities.Experimental results indicated that the proposed bio-method had the ability of controlling rainwater infiltration in term of varying rounds of biocement spraying treatment.In general,it was found that the rainwater infiltration decreases with the increase in slope angle and rainfall intensity.In the worst case of smallest slope angle(15°)and lightest rainfall intensity(n=50 mm/h),more than 82.6%,92.2%and 84.4%of rainwater were prevented from infiltration into the MICP treated natural sand,fine sand and medium sand,respectively,while the untreated soils were not able to prevent the rainwater infiltration at all.The corre-sponding maximum local uniaxial compressive strength for the MICP treated natural sand,fine sand and medium sand,respectively,were found to be 2.3 MPa,2.0 MPa,2.6 MPa,whereas the flexural stresses were 0.46 MPa,0.33 MPa,0.67 MPa,which could resist rainfall droplet impact force.Overall,the proposed bio-method showed good rainwater infiltration control capacity and high bearing strength against the impact of heavy rainfalls,suggesting a good potential to mitigate the rainfall-induced landslides.
文摘Microbially induced carbonate precipitation(MICP)is a new technology having the potential to induce soil stabilization and provide a green and sustainable comprehensive solution to some geotechnical engineering problems in the environment.The present article is dedicated to present a critical review of this technology and discuss its mechanisms of action and the key factors influencing its performance.The global experiences and national participation from Egypt are demonstrated,in addition to attempts for real life applications.This review provides an insight into the practical steps taken to mitigate some of the current limitations of MICP application and the identified gaps in analogous studies.It was concluded that integrating MICP with existing technologies would favor both engineering needs and market requirements.In addition,providing effective solutions to MICP limitations would highlight this technology as an eco-friendly and cost-effective option to several engineering obstacles.Finally,recommendations focused on encouraging global collaboration for knowledge transfer about this technology among different countries,as well as positive financial support from industrial entities to aid in the progress of scientific research and achieving large-scale applications in the near future,are provided.
基金the financial support through No.MOE2015-T2-2-142 provided by the Ministry of Education,SingaporeNo.SMI-2018-MA-02 by the Singapore Maritime Institute+1 种基金No.L2NICCFP2-2015-1 by the Singapore Ministry of National Developmentthe support of Centre for Urban Solutions,Nanyang Technological University.
文摘Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have been developed in recent years based on this approach.A proper understanding of the various approaches and the performances of different methods can help researchers and engineers to develop the most appropriate geotechnical solutions.At present,most of the methods can be categorized into three major types,biocementation,bioclogging,and biogas desaturation.Similarities and differences of different approaches and their potential applications are reviewed.Factors affecting the different processes are also discussed.Examples of up-scaled model tests and pilot trials are presented to show the emerging applications.The challenges and problems of biogeotechnology are also discussed.
