It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability a...It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported.For this,a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions(ψ_(ss)),initial void ratio of hosted clays(e_(c0))and void ratio at liquid limit of hosted clays(e_(cL)).The roles of ψ_(ss) in both the relationships of permeability coefficient of hosted clay(k_(v-hosted clay))versus effective vertical stress(σ'_(v))and void ratio of hosted clay(e_(c-hosted clay))versus σ'_(v) were analyzed.The results show that the permeability coefficient of reconstituted sandy clays(k_(v))is dominated by hosted clay(k_(v)=k_(v-hosted clay)).Both ψ_(ss) and σ'_(v) affect the k_(v) of sandy clays by changing the e_(c-hosted clay) at any given σ'_(v).Due to the partial contacts and densified clay bridges between the sand particles(i.e.structure effects),the e_(c-hosted clay) in sandy clays is higher than that in clays at the same σ'_(v)v.The k_(v)-e_(c-hosted clay) relationship of sandy clays is independent of σ'_(v) and ψ_(ss)but is a function of e_(cL).The types of hosted clays affect the k_(v) of sandy clays by changing the e_(cL).Based on the relationship between permeability coefficient and void ratio for the reconstituted clays,an empirical method for determining the k_(v) is proposed and validated for sandy clays.The predicted values are almost consistent with the measured values with k_(v-predicted)=k_(v-measured)=0.6-2.5.展开更多
Eco-geotechnical engineering plays a pivotal role in enhancing global sustainability and upholding the perfor-mance of earthen structures.The utilization of vegetation to stabilise geotechnical infrastructures is wide...Eco-geotechnical engineering plays a pivotal role in enhancing global sustainability and upholding the perfor-mance of earthen structures.The utilization of vegetation to stabilise geotechnical infrastructures is widely recognized and embraced for its environmentally friendly attributes.The spectre of climate change further in-tensifies the focus on the effects of temperature and humidity on vegetated soil.Consequently,there is a pressing need for research exploring the influence of changing climates on vegetated infrastructures.Such research de-mands a holistic and interdisciplinary approach,bridging fields such as soil mechanics,botany,and atmospheric science.This review underscores key facets crucial to vegetated geotechnical infrastructures,encompassing climate projections,centrifuge modelling,field monitoring,and numerical methodologies.展开更多
Soil contamination remains a global problem,and numerous studies have been published for investigating soil re-mediation.Thermal desorption remediation(TDR)can significantly reduce the contaminants in the soil within ...Soil contamination remains a global problem,and numerous studies have been published for investigating soil re-mediation.Thermal desorption remediation(TDR)can significantly reduce the contaminants in the soil within a short time and consequently has been used worldwide.However,the soil properties respond to TDR differently and are dependent on the experimental set-up.The causative mechanisms of these differences are yet to be fully elucidated.A statistical meta-analysis was thus undertaken to evaluate the TDR treatment effects on soil properties and plant per-formance.This review pointed out that soil clay was reduced by 54.2%,while soil sand content was enhanced by 15.2% after TDR.This might be due to the release of cementing agents from clay minerals that resulted in the formation of soil aggregates.Soil electrical conductivity enhanced by 69.5% after TDR,which might be due to the heating-induced loss of structural hydroxyl groups and the consequent liberation of ions.The treatment of TDR leads to the reduction of plant germination rate,length,and biomass by 19.4%,44.8%,and 20.2%,respectively,compared to that of control soil.This might be due to the residue of contaminants and the loss of soil fertility during the thermal process that inhibited plant germination and growth.Soil pH and sulfate content increased with heating temperature increased,while soil enzyme activities decreased with thermal temperature increased.Overall,the results suggested that TDR treatment has inhibited plant growth as well as ecological restoration.展开更多
Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years.Three 10 m5 m grassed plots were constructed in completely decomposed...Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years.Three 10 m5 m grassed plots were constructed in completely decomposed granitic soil.Two of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar amendment.During the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were measured.The monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,respectively.In the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised pronouncedly.The threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold RLD.The presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended plot.Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.展开更多
The combined effects of climate change and intensified engineering activities have increased soil-related hazards globally,such as slope failures and dust storms(Cui et al.,2021).Shallow landslides and surface erosion...The combined effects of climate change and intensified engineering activities have increased soil-related hazards globally,such as slope failures and dust storms(Cui et al.,2021).Shallow landslides and surface erosion frequently occur,particularly in response to heavy rainfall(Qin et al.,2022).These hazards result in the loss of human life and entail significant economic losses and environmental risks.Traditional engineering practices often use environmentally unfriendly materials,which have ecologically caused detrimental effects on geotechnical infrastructures.In recent years,people have been looking for more“green”solutions worldwide.Soil bioengineering using vegetation is a promising sustainable alternative and highly cost-effective strategy for strengthening topsoil so as to mitigate soil erosion and shallow landslides(Ng,2017).To address the issues encompassing social,environmental,ecological,and economic considerations,“green”engineering measures are suggested to promote sustainability by involving the vegetation approach(Rowe&Jefferis,2022).展开更多
The substantial generation of building waste had precipitated significant environmental issues in China,attributable to urban expansion.Recycled concrete aggregate(RCA)produced from building waste had been used as an ...The substantial generation of building waste had precipitated significant environmental issues in China,attributable to urban expansion.Recycled concrete aggregate(RCA)produced from building waste had been used as an alternative material in green roofs as substrates.However,the biological dynamics of RCA are unknown.Thus,the column test was performed to investigate the effects of different biochar types and application ratios on the biochemical properties and bacterial communities of RCA.Results show that the nutrients of RCA have been improved by biochar addition regardless of biochar types and application ratios.This led to the increase in plant weight and height by at least 227%and 38%in biochar amended RCA.However,biochar application reduced bacterial richness andα-diversity,while enhancing plant growth.This indicated that biochar application directly improves certain bacterial species that promote plant growth and productivity.Biochar application reduced the Proteobacteria abundance and enhanced the percentage of Acidobacteriota in RCA,indicating that biochar application shaped the bacterial communities into raw soil composition.The outcome of this research suggests that biochar application improved RCA biochemical performance as a substrate for green roofs,which provides a potential method to consume substantial RCA.展开更多
Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and field.However,no systemat...Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and field.However,no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs(FRC)and coarse-grained RCAs(CRC)that can be used for the three-layer landfill cover system.The aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of RCAs.The numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm,its saturated permeability increases by 10 times.As a result,a larger amount of rainwater infiltrates into the cover system,causing a higher lateral diversion in both the top FRC and middle CRC layers.No further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 mm.Both the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall event.This implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of materials.Although it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible,this study provides an upper limit to the particle size that can be used in the bottom layer(D10 not larger than 0.02 mm).With this limit,the three-layer system can still minimize the water percolation to meet the design criterion(30 mm/yr)even under a 100-year return period of rainfall in humid climates.展开更多
The increasing emission of greenhouse gases such as CO_(2),CH_(4),and N_(2)O from the soil has become a growing concern globally.To address this issue,biochar has emerged as an environmentally friendly soil amendment ...The increasing emission of greenhouse gases such as CO_(2),CH_(4),and N_(2)O from the soil has become a growing concern globally.To address this issue,biochar has emerged as an environmentally friendly soil amendment that can affect the gas permeability of soil and reduce greenhouse gas emissions.The biochar-soil-plant system exhibits a complicated interaction that promotes plant productivity and root elongation,further impacting greenhouse gas emissions.The objective of this paper is to provide a comprehensive review of the effects of biochar on soil gas permeability and consequently greenhouse gas emission in vegetated soil.The paper begins by discussing the basic characteristics of biochar and its impact on soil microstructure.It then explores the impact of biochar on the gas permeability of both non-vegetated and vegetated soil.The mechanisms through which biochar influences greenhouse gas emission are explained in terms of modified soil aeration,water holding capacity,adsorption,pH,available nutrients,and the activity of soil microbes and enzymes.The role of plants in greenhouse gas emission in biochar-amended soil is also analysed by comparing the vegetated group with the non-vegetation group.The paper includes a discussion of the various methods used to measure soil gas permeability,such as the steady-state and transient methods,as well as greenhouse gas emission measurement techniques,such as the chamber system and micrometeorological methods.Finally,future research directions are proposed to highlight the impact and corresponding mechanisms of plant roots on the biochar-induced variation of soil gas permeability and greenhouse gas emission.展开更多
Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of bi...Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory investigation.First,a gas permeability model was developed for vegetated coarse-grained soils with biochar addition.Then,a well-instrumented laboratory column test and two tests from the literature,considering bare,grass,biochar and grass+biochar conditions,were used for model validation.Finally,a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission rate.Results showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of saturation.The lowest water retention capacity,the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed column.However,adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability,resulting in the lowest gas emission rate.The measured gas emission rates for the four cases meet the recommended value by the design guideline.The parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170%in the grass case but decreased by 97%in the grass+biochar case.Under the severe drought condition with soil suction around 500 kPa,the gas emission rate in the grassed case exceeded the design value by 18%,while those in the biochar cases were far below the allowable value.Therefore,peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.52278334 and 4197724)Fundamental Research Funds for the Central Universities (Grant No.2242024k30066).
文摘It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported.For this,a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions(ψ_(ss)),initial void ratio of hosted clays(e_(c0))and void ratio at liquid limit of hosted clays(e_(cL)).The roles of ψ_(ss) in both the relationships of permeability coefficient of hosted clay(k_(v-hosted clay))versus effective vertical stress(σ'_(v))and void ratio of hosted clay(e_(c-hosted clay))versus σ'_(v) were analyzed.The results show that the permeability coefficient of reconstituted sandy clays(k_(v))is dominated by hosted clay(k_(v)=k_(v-hosted clay)).Both ψ_(ss) and σ'_(v) affect the k_(v) of sandy clays by changing the e_(c-hosted clay) at any given σ'_(v).Due to the partial contacts and densified clay bridges between the sand particles(i.e.structure effects),the e_(c-hosted clay) in sandy clays is higher than that in clays at the same σ'_(v)v.The k_(v)-e_(c-hosted clay) relationship of sandy clays is independent of σ'_(v) and ψ_(ss)but is a function of e_(cL).The types of hosted clays affect the k_(v) of sandy clays by changing the e_(cL).Based on the relationship between permeability coefficient and void ratio for the reconstituted clays,an empirical method for determining the k_(v) is proposed and validated for sandy clays.The predicted values are almost consistent with the measured values with k_(v-predicted)=k_(v-measured)=0.6-2.5.
文摘Eco-geotechnical engineering plays a pivotal role in enhancing global sustainability and upholding the perfor-mance of earthen structures.The utilization of vegetation to stabilise geotechnical infrastructures is widely recognized and embraced for its environmentally friendly attributes.The spectre of climate change further in-tensifies the focus on the effects of temperature and humidity on vegetated soil.Consequently,there is a pressing need for research exploring the influence of changing climates on vegetated infrastructures.Such research de-mands a holistic and interdisciplinary approach,bridging fields such as soil mechanics,botany,and atmospheric science.This review underscores key facets crucial to vegetated geotechnical infrastructures,encompassing climate projections,centrifuge modelling,field monitoring,and numerical methodologies.
基金the financial sponsorship from the National Key R&D Program of China(No.2023YFC3905800)Youth Innovation Promotion Association CAS(2021349)+5 种基金Guangdong Youth Talent Support Program(2021TQ06L121)State Key Laboratory of Subtropical Building Science in South China University of Technology(2022ZC01)Shenzhen Science and Technology Program(KCXFZ20211020163816023)financially supported by the Natural Science Foundation of Wuhan(No.2024040801020271)the Fundamental Research Funds for Central Public Welfare Research Institutes(No.CKSF20241004/YT)the support from FINNCERES flagship and tenure track fund(91160169(TT/Bordoloi)。
文摘Soil contamination remains a global problem,and numerous studies have been published for investigating soil re-mediation.Thermal desorption remediation(TDR)can significantly reduce the contaminants in the soil within a short time and consequently has been used worldwide.However,the soil properties respond to TDR differently and are dependent on the experimental set-up.The causative mechanisms of these differences are yet to be fully elucidated.A statistical meta-analysis was thus undertaken to evaluate the TDR treatment effects on soil properties and plant per-formance.This review pointed out that soil clay was reduced by 54.2%,while soil sand content was enhanced by 15.2% after TDR.This might be due to the release of cementing agents from clay minerals that resulted in the formation of soil aggregates.Soil electrical conductivity enhanced by 69.5% after TDR,which might be due to the heating-induced loss of structural hydroxyl groups and the consequent liberation of ions.The treatment of TDR leads to the reduction of plant germination rate,length,and biomass by 19.4%,44.8%,and 20.2%,respectively,compared to that of control soil.This might be due to the residue of contaminants and the loss of soil fertility during the thermal process that inhibited plant germination and growth.Soil pH and sulfate content increased with heating temperature increased,while soil enzyme activities decreased with thermal temperature increased.Overall,the results suggested that TDR treatment has inhibited plant growth as well as ecological restoration.
基金the financial sponsorship from the National Natural Science Foundation of China(Grant Nos.U20A20320,52308342)the Fundamental Research Funds for the Central Universities(Grant No.RF1028623071).
文摘Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years.Three 10 m5 m grassed plots were constructed in completely decomposed granitic soil.Two of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar amendment.During the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were measured.The monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,respectively.In the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised pronouncedly.The threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold RLD.The presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended plot.Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.
文摘The combined effects of climate change and intensified engineering activities have increased soil-related hazards globally,such as slope failures and dust storms(Cui et al.,2021).Shallow landslides and surface erosion frequently occur,particularly in response to heavy rainfall(Qin et al.,2022).These hazards result in the loss of human life and entail significant economic losses and environmental risks.Traditional engineering practices often use environmentally unfriendly materials,which have ecologically caused detrimental effects on geotechnical infrastructures.In recent years,people have been looking for more“green”solutions worldwide.Soil bioengineering using vegetation is a promising sustainable alternative and highly cost-effective strategy for strengthening topsoil so as to mitigate soil erosion and shallow landslides(Ng,2017).To address the issues encompassing social,environmental,ecological,and economic considerations,“green”engineering measures are suggested to promote sustainability by involving the vegetation approach(Rowe&Jefferis,2022).
基金the National Key R&D Program of China(No.2023YFC3905800)the State Key Laboratory of Subtropical Building and Urban Science in South China University of Technology(No.2022ZC01).
文摘The substantial generation of building waste had precipitated significant environmental issues in China,attributable to urban expansion.Recycled concrete aggregate(RCA)produced from building waste had been used as an alternative material in green roofs as substrates.However,the biological dynamics of RCA are unknown.Thus,the column test was performed to investigate the effects of different biochar types and application ratios on the biochemical properties and bacterial communities of RCA.Results show that the nutrients of RCA have been improved by biochar addition regardless of biochar types and application ratios.This led to the increase in plant weight and height by at least 227%and 38%in biochar amended RCA.However,biochar application reduced bacterial richness andα-diversity,while enhancing plant growth.This indicated that biochar application directly improves certain bacterial species that promote plant growth and productivity.Biochar application reduced the Proteobacteria abundance and enhanced the percentage of Acidobacteriota in RCA,indicating that biochar application shaped the bacterial communities into raw soil composition.The outcome of this research suggests that biochar application improved RCA biochemical performance as a substrate for green roofs,which provides a potential method to consume substantial RCA.
基金the financial sponsorship from the National Natural Science Foundation of China(Grant Nos.U20A20320 and 51778166)the funding from the State Key Laboratory of Subtropical Building Science in South China University of Technology(Grant No.2022ZC01).
文摘Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and field.However,no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs(FRC)and coarse-grained RCAs(CRC)that can be used for the three-layer landfill cover system.The aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of RCAs.The numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm,its saturated permeability increases by 10 times.As a result,a larger amount of rainwater infiltrates into the cover system,causing a higher lateral diversion in both the top FRC and middle CRC layers.No further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 mm.Both the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall event.This implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of materials.Although it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible,this study provides an upper limit to the particle size that can be used in the bottom layer(D10 not larger than 0.02 mm).With this limit,the three-layer system can still minimize the water percolation to meet the design criterion(30 mm/yr)even under a 100-year return period of rainfall in humid climates.
基金the Fundamental Research Funds for the Central Universities(4021002305)the funding from the State Key Laboratory of Subtropical Building Science in South China University of Technology(2022ZC01).
文摘The increasing emission of greenhouse gases such as CO_(2),CH_(4),and N_(2)O from the soil has become a growing concern globally.To address this issue,biochar has emerged as an environmentally friendly soil amendment that can affect the gas permeability of soil and reduce greenhouse gas emissions.The biochar-soil-plant system exhibits a complicated interaction that promotes plant productivity and root elongation,further impacting greenhouse gas emissions.The objective of this paper is to provide a comprehensive review of the effects of biochar on soil gas permeability and consequently greenhouse gas emission in vegetated soil.The paper begins by discussing the basic characteristics of biochar and its impact on soil microstructure.It then explores the impact of biochar on the gas permeability of both non-vegetated and vegetated soil.The mechanisms through which biochar influences greenhouse gas emission are explained in terms of modified soil aeration,water holding capacity,adsorption,pH,available nutrients,and the activity of soil microbes and enzymes.The role of plants in greenhouse gas emission in biochar-amended soil is also analysed by comparing the vegetated group with the non-vegetation group.The paper includes a discussion of the various methods used to measure soil gas permeability,such as the steady-state and transient methods,as well as greenhouse gas emission measurement techniques,such as the chamber system and micrometeorological methods.Finally,future research directions are proposed to highlight the impact and corresponding mechanisms of plant roots on the biochar-induced variation of soil gas permeability and greenhouse gas emission.
基金Fundamental Research Funds for the Central Universities(Grant No.3221002220A1)State Key Laboratory of Subtropical Building Science in South China University of Technology(Grant No.2022ZC01).
文摘Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory investigation.First,a gas permeability model was developed for vegetated coarse-grained soils with biochar addition.Then,a well-instrumented laboratory column test and two tests from the literature,considering bare,grass,biochar and grass+biochar conditions,were used for model validation.Finally,a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission rate.Results showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of saturation.The lowest water retention capacity,the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed column.However,adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability,resulting in the lowest gas emission rate.The measured gas emission rates for the four cases meet the recommended value by the design guideline.The parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170%in the grass case but decreased by 97%in the grass+biochar case.Under the severe drought condition with soil suction around 500 kPa,the gas emission rate in the grassed case exceeded the design value by 18%,while those in the biochar cases were far below the allowable value.Therefore,peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions.
