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
Biomineralization based on bacterial enzyme induced carbonate precipitation(BEICP)process is a promising alternative to cement-based ground treatment technology.The bacterial urease used in BEICP process is usually ul...Biomineralization based on bacterial enzyme induced carbonate precipitation(BEICP)process is a promising alternative to cement-based ground treatment technology.The bacterial urease used in BEICP process is usually ultrasonic extracted from urease-producing bacteria.To efficiently extract urease with relatively higher activity from bacterial cells,the ultrasonic extraction parameters of urease were optimized in this study.Next,a series of bacterial urease extraction tests and sand column treatment tests were conducted to investigate the effects of vibration amplitude,upper temperature limit,and cooling method on the urease extraction process and biomineralization of sand.The results show that the upper temperature limit is an important factor affecting the extraction efficiency and the activity of the extracted urease solution,and the optimum upper temperature limit is 50℃.The results indicate that increasing vibration amplitude could improve the extraction efficiency,but it hardly affects the urease activity(UA)under the optimal temperature.Continuous cooling could effectively simplify the operation and further improve the efficiency of urease extraction.Under the same urease activity of biotreatment solution,there is no marked difference in calcium carbonate content(CCC)and unconfined compressive strength of biomineralized sand columns prepared by urease solution extracted with different vibration amplitudes and upper temperature limits.The results of this study could provide a reference for application of BEICP technology of urease extraction to large-scale soil treatment.展开更多
[Objectives]Farmland ginseng cultivation,as a sustainable alternative to traditional forest-clearing ginseng planting,requires systematic evaluation of soil optimization strategies.This study aimed to quantify the lin...[Objectives]Farmland ginseng cultivation,as a sustainable alternative to traditional forest-clearing ginseng planting,requires systematic evaluation of soil optimization strategies.This study aimed to quantify the linkage between soil improvement outcomes and ginseng(Panax ginseng)yield across five regions in Yanbian Korean Autonomous Prefecture.[Methods]Soil improvement trials were conducted using farmland soils,with forest soils as the baseline.Soil nutrient contents were measured via soil agrochemical analysis method using a continuous flow analyzer.Statistical approaches,including significance tests,correlation analysis,and regression analysis,were applied to identify key factors influencing yield.[Results]Ginseng yield exhibited a significant positive correlation with organic matter content and available phosphorus,but a negative correlation with electrical conductivity,ammonium nitrogen,and available potassium.Wangqing and Liucai regions achieved post-improvement yields equivalent to 94%and 88%of forest soil yields,respectively,demonstrating the highest soil similarity to forest ecosystems.[Conclusions]Region-specific soil improvement protocols in Wangqing and Liucai show high replicability and efficacy.These strategies can serve as benchmarks for sustainable farmland ginseng cultivation,minimizing ecological disruption while maintaining productivity.展开更多
1.The key to achieving China’s dual carbon goals As pointed out in the CO_(2) Emissions in 2023 report released by the International Energy Agency,global carbon dioxide(CO_(2))emis-sions reached 37.4 billion tonnes i...1.The key to achieving China’s dual carbon goals As pointed out in the CO_(2) Emissions in 2023 report released by the International Energy Agency,global carbon dioxide(CO_(2))emis-sions reached 37.4 billion tonnes in 2023[1],setting a new record high.The increase in CO_(2) emissions has exacerbated global warm-ing and led to a series of global climate problems.China is a major emitter of CO_(2).展开更多
Sulfur-free lignin(SFL),a byproduct of the corn ethanol industry,effectively improves soil strength;however,its inherent solubility limits saline soil treatment in dry-wet environments.To solve this problem,this paper...Sulfur-free lignin(SFL),a byproduct of the corn ethanol industry,effectively improves soil strength;however,its inherent solubility limits saline soil treatment in dry-wet environments.To solve this problem,this paper proposes the selection of a granular SFL(GSFL)with a relatively large particle size,but with its chemical properties retained,to replace the conventional powdered SFL(PSFL).Among the processes of water-induced erosion failure of earthen structures,disintegration is commonly deemed the primary cause.Therefore,the disintegration characteristics of both PSFL-and GSFL-modified soils with 0%,5%,7%,10%,and 12%dosages were tested under dry-wet conditions.Moreover,several physicochemical properties,including the particle size distribution,bound water content,pH value,cation exchange capacity,functional groups,and microstructure,were explored.The results revealed that the water stability of the GSFL-modified soils was greater than that of the PSFL-modified soils.All of the PSFL-modified soils and natural soil completely disintegrated at the first immersion stage,whereas the GSFL-modified soils resisted 7 dry-wet cycles,notably at the 10%dosage.Microscopic analysis revealed that the SFL particle size affected mainly the cementation strength and microstructural homogeneity.Both the GSFL and PSFL particles strengthened the intergranular cementation through ion exchange,electrostatic interactions,and reinforcement effects.However,the PSFL preferentially filled the intragranular pores,causing a nonuniform microstructural arrangement and ineffectively enhancing the disintegration resistance of the saline soil.This preliminary study suggests that the particle size of a soil modifier may affect certain properties of the modified soil,necessitating future focused research.展开更多
Public urban greenery greatly contributes to the residential and tourist value of cities in the Gulf Region,but due to the hyper-arid climatic conditions,the cost of irrigation and plant maintenance is very high.Exist...Public urban greenery greatly contributes to the residential and tourist value of cities in the Gulf Region,but due to the hyper-arid climatic conditions,the cost of irrigation and plant maintenance is very high.Existing strategies to reduce the monetary and ecological costs involve the cultivation of native xerophytic plantations,and/or the use of soil improvers to increase water-and nutrient-holding capacity of the sandy soils.Various soil improvers based on mineral,organic,or synthetic materials have entered the United Arab Emirates(UAE)market in recent years,but there is considerable uncertainty about how they should best be used in combination with ornamental plant stands involving xerophytic native plants.The present study investigated the effect of soil amendment and deep pipe irrigation on perennial ornamental plant stands involving native plants(Tephrosia appolinea(Gel.)Link in combination with Aerva javanica(Burm.f.)Juss.ex Schult.)and native-exotic plants(T.appolinea in combination with Ruelia simplex C.Wright)either or not topsoil and subsoil amendment with bentonite and hydrophobic sand under the irrigation water supply of less than 50%of reference evapotranspiration(ET0).After one year of cultivation,T.appolinea and A.javanica(native vs.native)produced high biomass and exhibited high water use efficiency(WUE)as compared with T.appolinea and R.simplex(native vs.exotic)combination given that no significant differences were found under the soil amendment treatments.All stands thrived under irrigation water supply far below what is usually supplied to exotic ornamental stands in public parks of the Al Ain City,the UAE.However,subsoil amendment in combination with deep pipe irrigation reduced the occurrence of weeds and increased the overall plant rooting depth.Our results suggest that subsoil amendment and irrigation up to 60-80 cm depth can potentially control ephemeral weed infestation,which is a great challenge in various plant production systems of the Gulf Region.The results of the present study suggest that the impact of soil amendment on the WUE of exotic plants is marginal and might not be economically justified.Replacing exotic with native ornamental plant species seems to have a far greater water-saving potential than the amendment of the soil,while weeds can be suppressed in the absence of topsoil moisture.展开更多
Continuous cropping can bring economic benefits in a short time and meet the growing demand of agricultural products such as grain,but long-term continuous cropping will accelerate soil degradation,lead to the reducti...Continuous cropping can bring economic benefits in a short time and meet the growing demand of agricultural products such as grain,but long-term continuous cropping will accelerate soil degradation,lead to the reduction of crop yield and the increase of disease rate,and destroy the balance of soil microbial structure.Therefore,it is not conducive to the sustainable development of soil ecosystem.In this paper,the problems caused by continuous cropping,such as imbalance of soil microbial flora,decrease of biodiversity,accumulation of root exudates and their effects on soil fertility and crop growth,were summarized,and some measures were suggested to alleviate the obstacles of continuous cropping,such as reasonable rotation,adjustment of intercropping planting mode and application of biological fertilizers.Moreover,the paper also looked forward to the development trend of continuous cropping obstacle reduction techniques,including the integration and application of biological techniques,the promotion of green ecological techniques and the application of intelligent management system.This study provides theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promote the healthy and sustainable development of modern agriculture.展开更多
Continuous cropping has become a common form of agricultural production at present, but with the increase of continuous cropping years, continuous cropping obstacles such as soil-borne diseases and plant growth potent...Continuous cropping has become a common form of agricultural production at present, but with the increase of continuous cropping years, continuous cropping obstacles such as soil-borne diseases and plant growth potential decline are becoming more and more common. At present, the causes of continuous cropping obstacles and continuous cropping restoration have become a hot issue in agricultural research. This paper summarized the effects of continuous cropping obstacles on soil microbial community structure and main technical methods to repair continuous cropping obstacles, such as agricultural measure management, microbial balance adjustment and soil improvement, aiming to provide theoretical reference for protecting the sustainable utilization of soil ecosystem and ensuring the stability of crop production.展开更多
[Objectives]This study was conducted to further enrich the research on saline-alkali land improvement,and explore the effects of biological bacterial fertilizers containing Bacillus subtilis and Bacillus velezensis HM...[Objectives]This study was conducted to further enrich the research on saline-alkali land improvement,and explore the effects of biological bacterial fertilizers containing Bacillus subtilis and Bacillus velezensis HM-3 in saline-alkali land improvement and crop growth promotion.[Methods]Wheat was planted in saline-alkali land in Huanghua City,Hebei Province,and a mixed application experiment was carried out using biological agents from Hemiao Biotechnology Co.,Ltd.[Results]Compared with the field of control check(CK),water-soluble salts and pH value in the experimental fields decreased,and living bacteria count in the soil increased.Meanwhile,the economic characters of wheat in the experimental fields showed excellent performance,with yields increasing by 39.09%and 27.49%compared with the CK.It could be seen that the application of biological bacterial fertilizers achieved obvious effects of improving saline-alkali soil and increasing wheat yield.[Conclusions]In this study,the effects of biological bacterial fertilizers on saline-alkali land and wheat growth characters were clarified,providing some technical support and theoretical guidance for wheat planting in Huanghua saline-alkali land.展开更多
Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but...Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.展开更多
Soil desertification and salinization are the main environmental disasters in arid and semi-arid areas.It is of great significance to study the water-salt migration law of saline soil and propose corresponding water-s...Soil desertification and salinization are the main environmental disasters in arid and semi-arid areas.It is of great significance to study the water-salt migration law of saline soil and propose corresponding water-salt regulation and control measures.Microbial-induced calcite precipitation(MICP)technology was proposed to improve saline soil based on salt inhibition,and the water–salt–heat coupling migration law and salt-frost heave deformation law of saline soil before and after improvement were studied using soil column model tests.XR1#,XR2#(Saline-alkali-tolerant mineralization bacteria isolated from saline soil)and Sporosarcina pasteurii were used in the MICP improvement and the effect of XR1#was the best.Under high-temperature evaporation,the water migration change rate,water loss rate,accumulated evaporation amount,and accumulated salt content of the improved soil columns within a depth range of 0–40 cm were reduced by an average of 53.6%,47.3%,69.5%,and 40%,respectively,compared with the untreated soil column.During low-temperature cooling,the characteristics of water-salt migration changed significantly,and the deformation of salt-frost heave decreased significantly.The water-salt content at the freezing point(−4.5°C)changed from a cliff-like steep drop(untreated saline soil)to a slow decrease at environmental temperature(MICP-treated saline soil),and the amount of water crystallization decreased from 81%to 56.7%at−5°C.At the end of the cooling process,the amount of salt-frost heaving on the surface of the soil columns decreased by an average of 62.7%.Based on the measured data,a numerical simulation was conducted using the HYDRUS-1D model,which had good reliability and accurately simulated and predicted the law of water-salt migration in saline soil under the conditions of microbial solidification and improvement.MICP technology significantly reduced the change rate of water-salt migration and water evaporation in saline soil,hindered salt accumulation,and reduced salt-frost heave deformation,which effectively improved saline soil.The research results provide an important innovation and theoretical basis for the improvement of saline soil.展开更多
This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different ...This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.展开更多
At present,long-term continuous cropping in agricultural production has formed a relatively common development trend.With the increase of continuous cropping years,soil phenolic acids are also affected to varying degr...At present,long-term continuous cropping in agricultural production has formed a relatively common development trend.With the increase of continuous cropping years,soil phenolic acids are also affected to varying degrees.This paper summarized the effects of continuous cropping on soil phenolic acids and the research progress of continuous cropping obstacle reduction techniques,aiming at providing theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promoting the healthy and sustainable development of modern agriculture.展开更多
Soil is an essential component of what surrounds us in nature, providing as the basis for our infrastructure and construction. However, soil is not always suitable for construction due to a variety of geotechnical iss...Soil is an essential component of what surrounds us in nature, providing as the basis for our infrastructure and construction. However, soil is not always suitable for construction due to a variety of geotechnical issues such as inadequate bearing capacity, excessive settlement, and liquefaction susceptibility. Through improving the engineering qualities of soil, such as strength, permeability, and stability, ground grouting is a specific geotechnical method used. Using a fluid grout mixture injected into the subsurface, holes are filled and weak or loose strata are solidified as the material seeps into the soil matrix. The approach’s adaptability in addressing soil-related issues has made it more well-known in the fields of civil engineering and construction. In the end, this has improved groundwater management, foundation support, and overall geotechnical performance.展开更多
This study was conducted to study the feasibility of biochar in soil im- provement and tobacco quality. The black soil in NinganCountry of Mudanjiang was used as the material in this study, and the effects of biochar ...This study was conducted to study the feasibility of biochar in soil im- provement and tobacco quality. The black soil in NinganCountry of Mudanjiang was used as the material in this study, and the effects of biochar on tobacco-planting soil C/N, soil microorganisms, the development of tobacco, and chemical compo- nents and neutral aroma components in flue-cured tobacco werestudied. The results showed that the application of biochar at a rate of 1 800 kg/hm2 could increase soil C/N by 31.79%, and the quantity of actinomycetes in the soil was 3.8 times as much as that in control. The growth wasobviously better after biochar application, plant height and effective leaf number were significantly higher than those ofcontrol, but total sugar and nicotine were not significantly different. The application of biochar at a rate of 1 200 kg/hm2 increased the potassium content by 11%, the application of biochar at a rate of 2 400 kg/hm2 improved total sugar content by 5.40%, and the application of biochar at a rate of 1 800 kg/hm2 made the tobacco solanone content 1.97 times as that of control. Comprehensive studies showed that the application of biochar 1 200-1 800 kg/hm2 could improvesoilenvironment, and promote tobacco growth and quality.展开更多
Based on the geochemical data obtained from the national project about the prevention and control of soil contamination, this paper explored the properties of soil chemical elements in Huanghuaihai Plain, Shandong Pro...Based on the geochemical data obtained from the national project about the prevention and control of soil contamination, this paper explored the properties of soil chemical elements in Huanghuaihai Plain, Shandong Province. The results showed that among the grade-one nutritive elements in soil, organic matter, nitrogen and phosphorus were relatively deficient while potassium was rich. Meanwhile, as the grade-two nutritive elements, calcium oxide and magnesium oxide were relatively short and sulfur’s content was abundant. About the other beneficial and trace nutri-tive elements, iron oxide, manganese, molybdenum and boron were deficient, but the content of chlorine was high, hardly lack. The main barriers to improving land productivity were soil salinization and soil heavy metal contamination. The values of soil integrated fertility index that most of the soil in the study area is middle-lower fertilized. Specifical y, the low fertility area and lower fertility area are 6 1604 and 1 244 km2 respectively, occupying about 97.43% and 1.97% of the total area. The moderate fertility soil has an area of 172 km2, occupying about 0.27% of the total area. The higher fertility soil covers an area of 128 km2, while the high fertility area of only 76 km2. This article proposed scientific fertilization, elimination of soil obsta-cle, remediation of heavy-metal-contaminated soil and other effective measures to improve land productivity according to the basic investigation results, which provides a good technological support for the planning and development of good-quality and high-benefit agriculture.展开更多
Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel ente...Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel enterprises is a promising route to simultaneously address CO_(2)emissions and SS treatment. Recently, a serial of the relevant work focus on a single type ofsteel slag (SS), and the understanding of CO_(2) absorption by mineralization of various SS isvery lacking.Meanwhile, it is urgent requirement for systematic summary and discussion onhow to make full use of the mineralized products produced after the mineralization of CO_(2)in SS. This review aims to investigate the progress of CO_(2) mineralization using SS, includingthe potential applications of mineralization products, as well as the environmental impactand risk assessment ofmineralization product applications. Currently, the application of SSmineralization products is primarily focused on their use as construction materials with loweconomic value. With usage of the mineralization products for ecological restoration (e.g.sandy soil remediation) was treated as an advanced route, but still remaining challenge infunctional materials preparation, and its technical economy and possible hazards need tobe further explored by long-term experimental tests.展开更多
In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, ...In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, alkaline salt content, optimal irrigation, gypsum conversion, gypsum and soil treatment and improvement depth. The ions on the obtained filtrate were analyzed in terms of salts. The improving ef- ficiency of gypsum for meadow alkali soil was analyzed through comparing the con- tents of soluble salts in pre-improvement and post-improvement soil by reasoning and calculation. The results showed that, （1） the dissolved amount and conversion amount of gypsum were increased, and the soil alkalinity was decreased corre- spondingly with the increased irrigation amount. However, after reaching a certain extent, the linear relationships became unobvious gradually. Therefore, the irrigation amount should be arranged reasonably for different treatment. （2） Compared with those at low temperature, the dissolved amount of gypsum at high temperature was increased by 1.47-1.50 times, the release amount of exchangeable sodium was in- creased by 2.98-4.70 times, and the release amount of exchangeable magnesium was increased by 2.07-2.90 times. In overall, the improving efficiency of gypsum in summer was better. However, gypsum had two shortcomings in summer. First, a large amount of gypsum leaked away. Second, a large amount of exchangeable magnesium, along with exchangeable sodium, was substituted by gypsum. （3） Compared with the other two treatments, treatment B （mixing gypsum and top 20- cm soil） showed the best improving efficiency, and it was characterized by stepwise dealkalization from top to down. In addition, mixing gypsum and topsoil is more practical in the production.展开更多
This work’s aim is to participate in local materials (raw or fiber improved), which can be used in sustainable and accessible buildings to every Senegalese. To do this, studied materials are respectively collected fr...This work’s aim is to participate in local materials (raw or fiber improved), which can be used in sustainable and accessible buildings to every Senegalese. To do this, studied materials are respectively collected from a laterite clay pit in Ndouloumadjie Dembe (Matam, Northern Senegal) and another from a termite mound in Tattaguine (Fatick, Central Senegal). These samples are first subjected to Geotechnical identification tests. Mud bricks are then made with raw or sifted millet involucre improved to 1%, 2%, and 3% at 5 mm sieve samples. These briquettes are subjected to compression tests and thermal evaluations. Lagrange and Newton methods of numeric modelling are used to test the whole mixture points between 1% and 3% millet involucre for a better correlation between mechanical and thermal parameters. The results show that in Matam, as well as in Tattaguine, these muds, raw or improved, are of good thermomechanical quality when they are used in bricks making. And the thermomechanical coupling quality reaches a maximum situated at 2.125% for Ndouloumadjie and 2.05% for Tattaguine. These briquettes’ building quality depends on the mud content used in iron, aluminum, silica and clay. Thus, same natural materials can be used in the establishment of habitats according to their geotechnical, chemical, mechanical and thermal characteristics.展开更多
Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studi...Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.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 National Natural Science Foundation of China(NSFC)(Grant Nos.52108307 and 52178319)the Natural Science Foundation of Fujian Province,China(Grant No.2022J05020).
文摘Biomineralization based on bacterial enzyme induced carbonate precipitation(BEICP)process is a promising alternative to cement-based ground treatment technology.The bacterial urease used in BEICP process is usually ultrasonic extracted from urease-producing bacteria.To efficiently extract urease with relatively higher activity from bacterial cells,the ultrasonic extraction parameters of urease were optimized in this study.Next,a series of bacterial urease extraction tests and sand column treatment tests were conducted to investigate the effects of vibration amplitude,upper temperature limit,and cooling method on the urease extraction process and biomineralization of sand.The results show that the upper temperature limit is an important factor affecting the extraction efficiency and the activity of the extracted urease solution,and the optimum upper temperature limit is 50℃.The results indicate that increasing vibration amplitude could improve the extraction efficiency,but it hardly affects the urease activity(UA)under the optimal temperature.Continuous cooling could effectively simplify the operation and further improve the efficiency of urease extraction.Under the same urease activity of biotreatment solution,there is no marked difference in calcium carbonate content(CCC)and unconfined compressive strength of biomineralized sand columns prepared by urease solution extracted with different vibration amplitudes and upper temperature limits.The results of this study could provide a reference for application of BEICP technology of urease extraction to large-scale soil treatment.
基金Supported by National Natural Science Foundation Cultivation Project of Lishui University(036/2024)Municipal-Level Project:Pathways for Establishing Low-carbon Pilot Counties(FGLS202210).
文摘[Objectives]Farmland ginseng cultivation,as a sustainable alternative to traditional forest-clearing ginseng planting,requires systematic evaluation of soil optimization strategies.This study aimed to quantify the linkage between soil improvement outcomes and ginseng(Panax ginseng)yield across five regions in Yanbian Korean Autonomous Prefecture.[Methods]Soil improvement trials were conducted using farmland soils,with forest soils as the baseline.Soil nutrient contents were measured via soil agrochemical analysis method using a continuous flow analyzer.Statistical approaches,including significance tests,correlation analysis,and regression analysis,were applied to identify key factors influencing yield.[Results]Ginseng yield exhibited a significant positive correlation with organic matter content and available phosphorus,but a negative correlation with electrical conductivity,ammonium nitrogen,and available potassium.Wangqing and Liucai regions achieved post-improvement yields equivalent to 94%and 88%of forest soil yields,respectively,demonstrating the highest soil similarity to forest ecosystems.[Conclusions]Region-specific soil improvement protocols in Wangqing and Liucai show high replicability and efficacy.These strategies can serve as benchmarks for sustainable farmland ginseng cultivation,minimizing ecological disruption while maintaining productivity.
基金supported by the National Key Research and Development Program of China(2022YFC3901103)the National Natural Science Foundation of China(22288102)the Science and Technology Plan Project of the Xinjiang Production and Con-struction Crops(XPCC)(2023AB017-01).
文摘1.The key to achieving China’s dual carbon goals As pointed out in the CO_(2) Emissions in 2023 report released by the International Energy Agency,global carbon dioxide(CO_(2))emis-sions reached 37.4 billion tonnes in 2023[1],setting a new record high.The increase in CO_(2) emissions has exacerbated global warm-ing and led to a series of global climate problems.China is a major emitter of CO_(2).
基金funded by the National Natural Science Foundation of China(Grant Nos.42330708 and 42302329).
文摘Sulfur-free lignin(SFL),a byproduct of the corn ethanol industry,effectively improves soil strength;however,its inherent solubility limits saline soil treatment in dry-wet environments.To solve this problem,this paper proposes the selection of a granular SFL(GSFL)with a relatively large particle size,but with its chemical properties retained,to replace the conventional powdered SFL(PSFL).Among the processes of water-induced erosion failure of earthen structures,disintegration is commonly deemed the primary cause.Therefore,the disintegration characteristics of both PSFL-and GSFL-modified soils with 0%,5%,7%,10%,and 12%dosages were tested under dry-wet conditions.Moreover,several physicochemical properties,including the particle size distribution,bound water content,pH value,cation exchange capacity,functional groups,and microstructure,were explored.The results revealed that the water stability of the GSFL-modified soils was greater than that of the PSFL-modified soils.All of the PSFL-modified soils and natural soil completely disintegrated at the first immersion stage,whereas the GSFL-modified soils resisted 7 dry-wet cycles,notably at the 10%dosage.Microscopic analysis revealed that the SFL particle size affected mainly the cementation strength and microstructural homogeneity.Both the GSFL and PSFL particles strengthened the intergranular cementation through ion exchange,electrostatic interactions,and reinforcement effects.However,the PSFL preferentially filled the intragranular pores,causing a nonuniform microstructural arrangement and ineffectively enhancing the disintegration resistance of the saline soil.This preliminary study suggests that the particle size of a soil modifier may affect certain properties of the modified soil,necessitating future focused research.
基金partly funded by the Al Ain MunicipalityNational Water and Energy Center, United Arab Emirates University。
文摘Public urban greenery greatly contributes to the residential and tourist value of cities in the Gulf Region,but due to the hyper-arid climatic conditions,the cost of irrigation and plant maintenance is very high.Existing strategies to reduce the monetary and ecological costs involve the cultivation of native xerophytic plantations,and/or the use of soil improvers to increase water-and nutrient-holding capacity of the sandy soils.Various soil improvers based on mineral,organic,or synthetic materials have entered the United Arab Emirates(UAE)market in recent years,but there is considerable uncertainty about how they should best be used in combination with ornamental plant stands involving xerophytic native plants.The present study investigated the effect of soil amendment and deep pipe irrigation on perennial ornamental plant stands involving native plants(Tephrosia appolinea(Gel.)Link in combination with Aerva javanica(Burm.f.)Juss.ex Schult.)and native-exotic plants(T.appolinea in combination with Ruelia simplex C.Wright)either or not topsoil and subsoil amendment with bentonite and hydrophobic sand under the irrigation water supply of less than 50%of reference evapotranspiration(ET0).After one year of cultivation,T.appolinea and A.javanica(native vs.native)produced high biomass and exhibited high water use efficiency(WUE)as compared with T.appolinea and R.simplex(native vs.exotic)combination given that no significant differences were found under the soil amendment treatments.All stands thrived under irrigation water supply far below what is usually supplied to exotic ornamental stands in public parks of the Al Ain City,the UAE.However,subsoil amendment in combination with deep pipe irrigation reduced the occurrence of weeds and increased the overall plant rooting depth.Our results suggest that subsoil amendment and irrigation up to 60-80 cm depth can potentially control ephemeral weed infestation,which is a great challenge in various plant production systems of the Gulf Region.The results of the present study suggest that the impact of soil amendment on the WUE of exotic plants is marginal and might not be economically justified.Replacing exotic with native ornamental plant species seems to have a far greater water-saving potential than the amendment of the soil,while weeds can be suppressed in the absence of topsoil moisture.
基金Supported by Key Project of Yunnan Provincial Science and Technology Plan(202202AE090015)Scientific Research Fund of Yunnan Education Department(2024Y742+3 种基金2023Y0863)National Natural Science Foundation of China(42067009)2023 Undergraduate Innovation and Entrepreneurship Training Program of Yunnan Education Department(S202311393044S202311393061).
文摘Continuous cropping can bring economic benefits in a short time and meet the growing demand of agricultural products such as grain,but long-term continuous cropping will accelerate soil degradation,lead to the reduction of crop yield and the increase of disease rate,and destroy the balance of soil microbial structure.Therefore,it is not conducive to the sustainable development of soil ecosystem.In this paper,the problems caused by continuous cropping,such as imbalance of soil microbial flora,decrease of biodiversity,accumulation of root exudates and their effects on soil fertility and crop growth,were summarized,and some measures were suggested to alleviate the obstacles of continuous cropping,such as reasonable rotation,adjustment of intercropping planting mode and application of biological fertilizers.Moreover,the paper also looked forward to the development trend of continuous cropping obstacle reduction techniques,including the integration and application of biological techniques,the promotion of green ecological techniques and the application of intelligent management system.This study provides theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promote the healthy and sustainable development of modern agriculture.
基金Supported by National Natural Science Foundation of China(42067009)Scientific Research Project of Yunnan Provincial Department of Education(2024Y742,2023Y0863)+2 种基金Project of Kunming Municipal Commission of Development and Reform(Kunming Spring City Industrial Technology Leading Talents)Science and Technology Major Project of Yunnan Province Science and Technology Department(202202AE090015-02)Yunnan Students’innovation and entrepreneurship training program(S202311393044,S202311393061)。
文摘Continuous cropping has become a common form of agricultural production at present, but with the increase of continuous cropping years, continuous cropping obstacles such as soil-borne diseases and plant growth potential decline are becoming more and more common. At present, the causes of continuous cropping obstacles and continuous cropping restoration have become a hot issue in agricultural research. This paper summarized the effects of continuous cropping obstacles on soil microbial community structure and main technical methods to repair continuous cropping obstacles, such as agricultural measure management, microbial balance adjustment and soil improvement, aiming to provide theoretical reference for protecting the sustainable utilization of soil ecosystem and ensuring the stability of crop production.
基金Supported by Key Research and Development Program of Hebei Province(20322911D,21322903D)Innovation Ability Promotion Program of Hebei Province(20562903D)+1 种基金Technical Innovation Guidance Program of Hebei Province(20822904D)Science and Technology Research and Development Program of Qinhuangdao City(202201B028).
文摘[Objectives]This study was conducted to further enrich the research on saline-alkali land improvement,and explore the effects of biological bacterial fertilizers containing Bacillus subtilis and Bacillus velezensis HM-3 in saline-alkali land improvement and crop growth promotion.[Methods]Wheat was planted in saline-alkali land in Huanghua City,Hebei Province,and a mixed application experiment was carried out using biological agents from Hemiao Biotechnology Co.,Ltd.[Results]Compared with the field of control check(CK),water-soluble salts and pH value in the experimental fields decreased,and living bacteria count in the soil increased.Meanwhile,the economic characters of wheat in the experimental fields showed excellent performance,with yields increasing by 39.09%and 27.49%compared with the CK.It could be seen that the application of biological bacterial fertilizers achieved obvious effects of improving saline-alkali soil and increasing wheat yield.[Conclusions]In this study,the effects of biological bacterial fertilizers on saline-alkali land and wheat growth characters were clarified,providing some technical support and theoretical guidance for wheat planting in Huanghua saline-alkali land.
基金the Key Research Program of Shanghai Construction Group(No.17JCSF-37)。
文摘Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.
基金funded by grants from the National Natural Science Foundation of China(No.51968057),(No.52378348),(No.12262031)Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2023QN04016),(No.2019LH05028)+1 种基金Basic scientific research business fees for universities directly under the Inner Mongolia Autonomous Region of China(No.JY20220204)Doctoral Research Foundation of Inner Mongolia University of Technology of China(No.DC2300001265).
文摘Soil desertification and salinization are the main environmental disasters in arid and semi-arid areas.It is of great significance to study the water-salt migration law of saline soil and propose corresponding water-salt regulation and control measures.Microbial-induced calcite precipitation(MICP)technology was proposed to improve saline soil based on salt inhibition,and the water–salt–heat coupling migration law and salt-frost heave deformation law of saline soil before and after improvement were studied using soil column model tests.XR1#,XR2#(Saline-alkali-tolerant mineralization bacteria isolated from saline soil)and Sporosarcina pasteurii were used in the MICP improvement and the effect of XR1#was the best.Under high-temperature evaporation,the water migration change rate,water loss rate,accumulated evaporation amount,and accumulated salt content of the improved soil columns within a depth range of 0–40 cm were reduced by an average of 53.6%,47.3%,69.5%,and 40%,respectively,compared with the untreated soil column.During low-temperature cooling,the characteristics of water-salt migration changed significantly,and the deformation of salt-frost heave decreased significantly.The water-salt content at the freezing point(−4.5°C)changed from a cliff-like steep drop(untreated saline soil)to a slow decrease at environmental temperature(MICP-treated saline soil),and the amount of water crystallization decreased from 81%to 56.7%at−5°C.At the end of the cooling process,the amount of salt-frost heaving on the surface of the soil columns decreased by an average of 62.7%.Based on the measured data,a numerical simulation was conducted using the HYDRUS-1D model,which had good reliability and accurately simulated and predicted the law of water-salt migration in saline soil under the conditions of microbial solidification and improvement.MICP technology significantly reduced the change rate of water-salt migration and water evaporation in saline soil,hindered salt accumulation,and reduced salt-frost heave deformation,which effectively improved saline soil.The research results provide an important innovation and theoretical basis for the improvement of saline soil.
基金supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,PR China(Project Nos.HKU 17207518 and R5037-18).
文摘This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.
基金Supported by Scientific Research Fund of Yunnan Education Department(2024Y742,2023Y0863)National Natural Science Foundation of China(42067009)+1 种基金College Students'Innovative Training Plan Program of Yunnan Education Department in 2023(S202311393044,S202311393061)Key Project of Science and Technology Program of Yunnan Province(202202AE090015).
文摘At present,long-term continuous cropping in agricultural production has formed a relatively common development trend.With the increase of continuous cropping years,soil phenolic acids are also affected to varying degrees.This paper summarized the effects of continuous cropping on soil phenolic acids and the research progress of continuous cropping obstacle reduction techniques,aiming at providing theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promoting the healthy and sustainable development of modern agriculture.
文摘Soil is an essential component of what surrounds us in nature, providing as the basis for our infrastructure and construction. However, soil is not always suitable for construction due to a variety of geotechnical issues such as inadequate bearing capacity, excessive settlement, and liquefaction susceptibility. Through improving the engineering qualities of soil, such as strength, permeability, and stability, ground grouting is a specific geotechnical method used. Using a fluid grout mixture injected into the subsurface, holes are filled and weak or loose strata are solidified as the material seeps into the soil matrix. The approach’s adaptability in addressing soil-related issues has made it more well-known in the fields of civil engineering and construction. In the end, this has improved groundwater management, foundation support, and overall geotechnical performance.
基金Supported by Scientific and Technological Development Project of Tobacco Industry in Helongjiang Province(HYK[2015]59)~~
文摘This study was conducted to study the feasibility of biochar in soil im- provement and tobacco quality. The black soil in NinganCountry of Mudanjiang was used as the material in this study, and the effects of biochar on tobacco-planting soil C/N, soil microorganisms, the development of tobacco, and chemical compo- nents and neutral aroma components in flue-cured tobacco werestudied. The results showed that the application of biochar at a rate of 1 800 kg/hm2 could increase soil C/N by 31.79%, and the quantity of actinomycetes in the soil was 3.8 times as much as that in control. The growth wasobviously better after biochar application, plant height and effective leaf number were significantly higher than those ofcontrol, but total sugar and nicotine were not significantly different. The application of biochar at a rate of 1 200 kg/hm2 increased the potassium content by 11%, the application of biochar at a rate of 2 400 kg/hm2 improved total sugar content by 5.40%, and the application of biochar at a rate of 1 800 kg/hm2 made the tobacco solanone content 1.97 times as that of control. Comprehensive studies showed that the application of biochar 1 200-1 800 kg/hm2 could improvesoilenvironment, and promote tobacco growth and quality.
基金Supported by Multi-goal Geochemical Survey in Laoling-Hekou Regions,Shandong Province of National Soil Survey and Pollution Prevention(GZTR20060104)~~
文摘Based on the geochemical data obtained from the national project about the prevention and control of soil contamination, this paper explored the properties of soil chemical elements in Huanghuaihai Plain, Shandong Province. The results showed that among the grade-one nutritive elements in soil, organic matter, nitrogen and phosphorus were relatively deficient while potassium was rich. Meanwhile, as the grade-two nutritive elements, calcium oxide and magnesium oxide were relatively short and sulfur’s content was abundant. About the other beneficial and trace nutri-tive elements, iron oxide, manganese, molybdenum and boron were deficient, but the content of chlorine was high, hardly lack. The main barriers to improving land productivity were soil salinization and soil heavy metal contamination. The values of soil integrated fertility index that most of the soil in the study area is middle-lower fertilized. Specifical y, the low fertility area and lower fertility area are 6 1604 and 1 244 km2 respectively, occupying about 97.43% and 1.97% of the total area. The moderate fertility soil has an area of 172 km2, occupying about 0.27% of the total area. The higher fertility soil covers an area of 128 km2, while the high fertility area of only 76 km2. This article proposed scientific fertilization, elimination of soil obsta-cle, remediation of heavy-metal-contaminated soil and other effective measures to improve land productivity according to the basic investigation results, which provides a good technological support for the planning and development of good-quality and high-benefit agriculture.
基金supported by the National Key Research and Development Program(Nos.2023YFC3707101 and 2023YFF0614301)the Tsinghua University Initiative Scientific Research Program(No.2023Z02JMP001)the Linghang Project of School of Environment(No.025108011).
文摘Carbon dioxide (CO_(2)) mineralization technology has attracted significant attention, due tothe synergistic terminal treatment of CO_(2) and industrial waste. The combined CO_(2) mineralizationprocess with steel enterprises is a promising route to simultaneously address CO_(2)emissions and SS treatment. Recently, a serial of the relevant work focus on a single type ofsteel slag (SS), and the understanding of CO_(2) absorption by mineralization of various SS isvery lacking.Meanwhile, it is urgent requirement for systematic summary and discussion onhow to make full use of the mineralized products produced after the mineralization of CO_(2)in SS. This review aims to investigate the progress of CO_(2) mineralization using SS, includingthe potential applications of mineralization products, as well as the environmental impactand risk assessment ofmineralization product applications. Currently, the application of SSmineralization products is primarily focused on their use as construction materials with loweconomic value. With usage of the mineralization products for ecological restoration (e.g.sandy soil remediation) was treated as an advanced route, but still remaining challenge infunctional materials preparation, and its technical economy and possible hazards need tobe further explored by long-term experimental tests.
基金Supported by National Natural Science Foundation of China(41401559)Project of Hubei Provincial Science and Technology Department(2014CFB558)Project of Hubei Provincial Department of Education(D20141001)~~
文摘In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, alkaline salt content, optimal irrigation, gypsum conversion, gypsum and soil treatment and improvement depth. The ions on the obtained filtrate were analyzed in terms of salts. The improving ef- ficiency of gypsum for meadow alkali soil was analyzed through comparing the con- tents of soluble salts in pre-improvement and post-improvement soil by reasoning and calculation. The results showed that, （1） the dissolved amount and conversion amount of gypsum were increased, and the soil alkalinity was decreased corre- spondingly with the increased irrigation amount. However, after reaching a certain extent, the linear relationships became unobvious gradually. Therefore, the irrigation amount should be arranged reasonably for different treatment. （2） Compared with those at low temperature, the dissolved amount of gypsum at high temperature was increased by 1.47-1.50 times, the release amount of exchangeable sodium was in- creased by 2.98-4.70 times, and the release amount of exchangeable magnesium was increased by 2.07-2.90 times. In overall, the improving efficiency of gypsum in summer was better. However, gypsum had two shortcomings in summer. First, a large amount of gypsum leaked away. Second, a large amount of exchangeable magnesium, along with exchangeable sodium, was substituted by gypsum. （3） Compared with the other two treatments, treatment B （mixing gypsum and top 20- cm soil） showed the best improving efficiency, and it was characterized by stepwise dealkalization from top to down. In addition, mixing gypsum and topsoil is more practical in the production.
文摘This work’s aim is to participate in local materials (raw or fiber improved), which can be used in sustainable and accessible buildings to every Senegalese. To do this, studied materials are respectively collected from a laterite clay pit in Ndouloumadjie Dembe (Matam, Northern Senegal) and another from a termite mound in Tattaguine (Fatick, Central Senegal). These samples are first subjected to Geotechnical identification tests. Mud bricks are then made with raw or sifted millet involucre improved to 1%, 2%, and 3% at 5 mm sieve samples. These briquettes are subjected to compression tests and thermal evaluations. Lagrange and Newton methods of numeric modelling are used to test the whole mixture points between 1% and 3% millet involucre for a better correlation between mechanical and thermal parameters. The results show that in Matam, as well as in Tattaguine, these muds, raw or improved, are of good thermomechanical quality when they are used in bricks making. And the thermomechanical coupling quality reaches a maximum situated at 2.125% for Ndouloumadjie and 2.05% for Tattaguine. These briquettes’ building quality depends on the mud content used in iron, aluminum, silica and clay. Thus, same natural materials can be used in the establishment of habitats according to their geotechnical, chemical, mechanical and thermal characteristics.
基金supported by the National Parks Board,Singapore,and the Cities of Tomorrow R&D programme(Grant No.COT-V1-2020-4)by Ministry of National Development and National Research Foundation,Singapore.
文摘Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.
