This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The ...This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The impact of SDG components on the strength and durability of solidified soil was analysed through a series of tests,including unconfined compressive strength,water stability coefficient,water absorption rate,drying-wetting cycles,and shrinkage tests.Furthermore,microstructure characteristics were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM).The study shows that the solidified soil has excellent strength and durability when the SDG stabilizer contains 60% GGBGS,10% DG,and 30% CCS.Additionally,increasing the DG content negatively affects the soil's resistance to water.The SDG stabilizer has potential chemical cementitious characteristics and the calcium carbide slag is rich in calcium ions,which undergo an ion exchange reaction with minerals in the soil.These findings offer new ideas for the development of soil stabilizers.展开更多
The research analyzed characters of soil stabilizer and detailed the solidification mechanism.Furthermore,new type soil stabilizer Q2 was used in a base of Beijing Vocational College of Agriculture and a solidified ro...The research analyzed characters of soil stabilizer and detailed the solidification mechanism.Furthermore,new type soil stabilizer Q2 was used in a base of Beijing Vocational College of Agriculture and a solidified road with length of 250 m,width of 4 m and thickness of 0.25 m were constructed.The road was tested with an agricultural truck and subgrade tolerance to freezing was tested also.It is suggested that new type soil stabilizer would reduce construction cost of road,protect environment,and reduce construction period,with high value of application.展开更多
The change in the thickness of water films of special clay particles such as sliding clay, red clay, and expansive clay is an important factor in producing geological disasters and geological environmental damage. In ...The change in the thickness of water films of special clay particles such as sliding clay, red clay, and expansive clay is an important factor in producing geological disasters and geological environmental damage. In order to reduce the thickness of water films, ionic soil stabilizer （ISS） is used to treat sliding clay, red clay, and expansive clay. Direct shear test of sliding clay and shrinkage, free swell rate, zeta potential, and cation-exchange capacity of red clay and expansive clay are carried out. The results show that as the plastic indexes of special clay soil decrease, the shear strength of sliding clay increases, the shrinkage and free swell rate of red clay and expansive clay decrease, and the thickness of the water film thins after treatment with the ionic soil stabilizer. Therefore, the geological engineering disasters caused by changes in the thickness of water films of special clay can be effectively inhibited.展开更多
In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental sch...In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental scheme.Three levels o f each factor armconsidered to obtain the change laws o f UCS,in which the binder dosages are8%,10%,and12%;the curing times ae7,14and21d;the gradation nae0.3,0.35and0.4;and the degrees of compaction are95%,97%,and99%.The range analysis clearly indicates that the influence degree o f the four factors on UCS is in such an order:dosage,age,gradation,and degree o f compaction.The variance analysis shows that only the composite soil stabilizer dosage can significantly affect UCS.In road construction,the examination o f composite soil stabilizer dosage and base-course maintenance should be given much more attention to obtain satisfactory base-course strength,compared w ith gradation floating and the change of degree o f compaction.展开更多
A stabilized soil structure formation model was introduced. In order to form compact stabilized soil structure, cementitious hydrates were needed to wrap and bind the soil aggregates. Meanwhile, expansible hydrates we...A stabilized soil structure formation model was introduced. In order to form compact stabilized soil structure, cementitious hydrates were needed to wrap and bind the soil aggregates. Meanwhile, expansible hydrates were needed to squeeze and fill the pores, especially the pores in the aggregates. The experimental results show that the influences of various chemical characteristic factors of soil on the strength of the stabilized soil are boiled down, for the influence on the concentration of Ca（OH）2 in the pore solution of the stabilized soil, and the amount of CSH generated by cement. Finally an optimization design method is proposed, with which the stabilizer can be designed according to characteristics of soil samples.展开更多
The impact mechanism of vegetation on slope soil water infiltration and stability in the loess areas of the northeastern Qinghai-Tibet Plateau remains unclear.Understanding this mechanism is crucial for regional ecolo...The impact mechanism of vegetation on slope soil water infiltration and stability in the loess areas of the northeastern Qinghai-Tibet Plateau remains unclear.Understanding this mechanism is crucial for regional ecological restoration and shallow geological disaster prevention.This study investigated slopes covered by Caragana korshinskii Kom.by employing double-ring infiltration tests to explore the permeability characteristics and influencing factors of root-containing soils and to propose an appropriate infiltration model.Considering the synergistic effects of the canopy and roots,the hydrological response and stability of vegetation-covered slopes under rainfall infiltration conditions were evaluated through numerical simulation analysis.The results revealed that within the main root distribution layer(0-0.5 m),the initial and average infiltration rates and the permeability coefficient of the root-soil composite were significantly higher than those of bare land.Coarse roots with diameters of>5 mm were the key contributors to enhancement of the infiltration capacity.The dry density,fine particle content,and initial water content of the soil around the roots were negatively correlated with the infiltration process.The Horton model effectively reproduced the infiltration process under the canopy and on bare land.The roots significantly accelerated the advance of the slope wetting front during rainfall infiltration,whereas the canopy delayed its onset and progression.The rainfall infiltration process on vegetation-covered slopes was divided into three stages:the equilibrium infiltration stage,optimal infiltration stage beneath the canopy,and secondary equilibrium stage.Vegetation enhances slope stability through coupling of the canopy and root,with an order of canopy-root mode>root mode>bare slope.Under heavy rainfall conditions,the direct contribution of canopy interception to slope stability is limited,and its primary role is to delay the occurrence of instability.During this period,the mechanical effect of roots becomes the dominant mechanism in slope protection.展开更多
Unconfined Compressive Strength(UCS)is a key parameter for the assessment of the stability and performance of stabilized soils,yet traditional laboratory testing is both time and resource intensive.In this study,an in...Unconfined Compressive Strength(UCS)is a key parameter for the assessment of the stability and performance of stabilized soils,yet traditional laboratory testing is both time and resource intensive.In this study,an interpretable machine learning approach to UCS prediction is presented,pairing five models(Random Forest(RF),Gradient Boosting(GB),Extreme Gradient Boosting(XGB),CatBoost,and K-Nearest Neighbors(KNN))with SHapley Additive exPlanations(SHAP)for enhanced interpretability and to guide feature removal.A complete dataset of 12 geotechnical and chemical parameters,i.e.,Atterberg limits,compaction properties,stabilizer chemistry,dosage,curing time,was used to train and test the models.R2,RMSE,MSE,and MAE were used to assess performance.Initial results with all 12 features indicated that boosting-based models(GB,XGB,CatBoost)exhibited the highest predictive accuracy(R^(2)=0.93)with satisfactory generalization on test data,followed by RF and KNN.SHAP analysis consistently picked CaO content,curing time,stabilizer dosage,and compaction parameters as the most important features,aligning with established soil stabilization mechanisms.Models were then re-trained on the top 8 and top 5 SHAP-ranked features.Interestingly,GB,XGB,and CatBoost maintained comparable accuracy with reduced input sets,while RF was moderately sensitive and KNN was somewhat better owing to reduced dimensionality.The findings confirm that feature reduction through SHAP enables cost-effective UCS prediction through the reduction of laboratory test requirements without significant accuracy loss.The suggested hybrid approach offers an explainable,interpretable,and cost-effective tool for geotechnical engineering practice.展开更多
Global grassland degradation necessitates the identification of sustainable grazing management strategies.In semi-arid regions,grazing exclusion(GE),cold-season grazing(CG),and free grazing(FG)represent common practic...Global grassland degradation necessitates the identification of sustainable grazing management strategies.In semi-arid regions,grazing exclusion(GE),cold-season grazing(CG),and free grazing(FG)represent common practices in grassland ecosystems,yet the long-term ecological consequences of these patterns on plant community structure and soil aggregate stability remain inadequately elucidated.In this study,we evaluated the effects of GE,CG,and FG on soil organic carbon,soil water content,soil bulk density,soil aggregates,and vegetation indicators in Xilamuren steppe,a semi-arid grassland in northern China through field sampling and laboratory analyses in 2024.Our findings revealed that,compared to CG and FG,GE significantly enhanced aboveground and belowground biomass,species diversity,and soil physical-chemical properties in the 0–30 cm layer.The dominant plant species in GE and CG sites were Stipa krylovii,Leymus chinensis,and Agropyron cristatum,whereas Stipa krylovii,Artemisia frigida,and Leymus chinensis were predominant in FG site.Different grazing patterns led to distinct soil aggregate distributions,with>2.00 and<0.25 mm aggregates exhibiting the highest content in different soil layers depending on the grazing patterns.All grazing management strategies significantly improved soil aggregate stability,with the overall stability following the order:GE>CG>FG.Furthermore,random forest modeling identified plant species diversity,plant growth traits,and grazing patterns as the primary determinants of soil aggregate stability.Collectively,these results offer valuable insights into the sustainable management and ecological restoration of semi-arid grasslands under different grazing pressures.展开更多
This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main cr...This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.展开更多
We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing al...We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing alkali-activated sewage sludge(AASS)as a binder for stabilizing the clayey soil.Sewage sludge(SS)in varying proportions of 1.5%,2%,2.5%,3.5%,and 4.5%was utilized to prepare geopolymer binders using sodium and potassium-based alkali activators.Furthermore,unconfined compressive strength(UCS)and direct shear tests were conducted to examine the strength development of clayey soil stabilized with AASS.While the study presented some intriguing results,we have identified critical concerns regarding(i)the selection of SS as a precursor for alkali activation,(ii)technical inconsistencies associated with the compaction characteristics and microstructural analysis,and(iii)the feasibility of the proposed methodology for practical applications.Through our discussion,we seek to highlight these issues and provide constructive feedback to advance the understanding of alkali activation processes and their implications for soil stabilization.展开更多
A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a ba...A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a basic understanding of aggregate formation and stabilization,the functional relationship between aggregate stability and erosion resistance under extended sugarcane monoculture remains inadequately characterized.We employed an integrated methodology combining dry/wet sieving,the Le Bissonnais method and scanning electron microscopy to quantitatively evaluate the soil aggregate stability and erosion resistance across six distinct cultivation chrono-sequences(3–32 years)and two soil depths(0–15 cm and 15–30 cm)in the sugarcane cultivation area of Qingshui Village,Wuxuan County,Guangxi Zhuang Autonomous Region,China,aiming at providing insights for developing soil conservation strategies in sugarcane cultivation systems.The results reveal three core findings.First,planting years significantly influence the proportions of soil aggregates with varying particle sizes.Under the treatments with Le Bissonais methods,the mean weight diameter(MWD)under fast wetting,disturbance after pre-wetting,and slow wetting decrease with increasing planting years,while the relative dissipation index,relative mechanical fragmentation index,and erodibility factor(K)exhibit varying degrees of change,indicating progressive soil structural degradation and increased erosion susceptibility.Second,long-term sugarcane monocropping leads to declining soil organic carbon,liquid limit,plastic limit,and clay content,likely due to factors such as soil-forming materials and rainfall.Concurrently,the increased sand content and porosity weaken interparticle bonding and reducing aggregate stability over time.Third,correlation analysis demonstrates that MWD and geometric mean diameter(GMD)under disturbance after pre-wetting and slow wetting treatments show strong positive correlations with soil organic carbon,p H,clay content,liquid limit,and plastic limit but negative correlations with sand content,total porosity,and capillary porosity.Furthermore,K is significantly negatively correlated with soil physicochemical properties as well as GMD and MWD.These results help us understand the mechanism of aggregate stability variation in sugarcane-cultivated red soils and support the development of soil conservation strategies for sustaining sugarcane productivity in subtropical regions.展开更多
In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear str...In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear strength are indicators that reflect soil resistance to erosion and its ability to prevent shallow landslides,respectively.However,limited research has focused on the response of soil aggregate stability and shear strength to reforestation.We selected three types of reforestations(Phyllostachys edulis forest,Cunninghamia lanceolata(Lamb.)Hook.forest,Citrus sinensis(L.)Osbeck.orchard),a natural forest(mixed coniferous and broadleaf forests),and a fallow land as study plots,and measured root traits,and soil physicochemical traits,i.e.,pH,soil organic matter(SOC),Soil water content(SWC),soil bulk density(BD),soil cohesion(c),soil internal friction angle(φ)and analyzed their multiple interactions.The soil aggregate stability traits,refer to the mean weight diameter(MWD)and geometric mean diameter(GMD),exhibited a significant increase in reforested plots,approximately 200%compared to fallow land and 50%compared to natural forests.For soil shear strength the values were approximately 20%higher than in fallow land and approximately 10%lower than in natural forests.Soil aggregate stability and soil shear strength did not exhibit a significant positive correlation across all plots,and the underlying drivers of these traits were variable.For instance,in natural forest and timber stands,soil aggregate stability was mainly influenced by soil organic carbon,while soil shear strength was primarily affected by root length density.In economic forest,aggregate stability and shear strength are mainly affected by organic carbon.Overall,we found that vegetation restoration enhances soil erosion resistance,however,the primary drivers for the improvement of aggregate stability(soil organic carbon)and shear strength(root length density)are different.Therefore,in future benefit assessments of vegetation restoration projects aimed at soil erosion control,different indicators should be considered based on specific conditions.展开更多
The sustainable geotechnical approach for addressing the challenges associated with clayey soils at construction sites involves the modification of these soils’mechanical and chemical characteristics using soil enhan...The sustainable geotechnical approach for addressing the challenges associated with clayey soils at construction sites involves the modification of these soils’mechanical and chemical characteristics using soil enhancement methods.The present study investigates the coupling effect of sandstone slurry waste(SSW)and calcium carbonate nanoparticle(CCN)as potential stabilizers to enhance the characteristics of clayey soil.A comprehensive investigation was conducted using compaction tests,plasticity index(PI)tests,California bearing ratio(CBR)tests,unconfined compressive strength(UCS)tests,and microstructural analyses of clayey soil,SSW and SSW-CCN-treated clay samples containing 5%,10%,15%,20%,25%,30%,and 35%SSW and 0.3%,0.6%,0.9%,1.2%,and 1.5%CCN mixed with clayey soil in different combinations of clay,SSW,and CCN.The findings reveal that incorporating 25%SSW with 0.9%CCN into clay soil results in an increase in the UCS from 132.2 kPa for untreated clayey soil without curing to 263 kPa after a 28-d curing period.Similarly,a rising trend in CBR results is observed up to 25%SSW addition in clay soil and up to 0.9%CCN addition in SSW-clay mixture.Initially,notable enhancements in UCS were attributed to a denser soil structure,followed by the formation of calcium–silicate–hydrate(CSH)gel,which intensified with prolonged curing.Gel patches were detected by scanning electron microscopy(SEM)in addition to particle aggregation.The results obtained from thermogravimetric analysis,Fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)supported the presence of hydration products such as CSH.The experimental study indicates that SSW,in combination with CCN,offers a sustainable alternative to traditional soil stabilizers.展开更多
A plastic mixture construction technology using MBER （material becoming earth into rock） soil stabilizer is introduced and the water quality of a solidified soil cistern using the technology is analyzed. Rainwater w...A plastic mixture construction technology using MBER （material becoming earth into rock） soil stabilizer is introduced and the water quality of a solidified soil cistern using the technology is analyzed. Rainwater was harvested in July, 2012. Water quality of runoff and cistern water after storage was measured, including turbidity, chemical oxygen demand （COD）, total nitrogen, nitrate, and ammonia. Results show that pollutant concentrations in runoff decreased with time, indicating that runoff in the early time should be removed. Nitrate concentrations in cistern water increased after storage, while the remaining parameters decreased. Measured pollutant concentrations did not exceed the limit according to the standard for drinking water in China. It can be concluded that the solidified soil cistern with plastic mixture construction technology can provide available water for domestic use.展开更多
Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs...Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.展开更多
To improve the applicability of red mud in subgrade construction,we studied the effects of four traditional retarders,including borax,sodium hexametaphosphate,sodium gluconate,and sucrose,on the setting time,mechanica...To improve the applicability of red mud in subgrade construction,we studied the effects of four traditional retarders,including borax,sodium hexametaphosphate,sodium gluconate,and sucrose,on the setting time,mechanical properties and soil solidification of red mud-based subgrade engineered cementitious material(RCM).The mechanisms of the retarders on the hydration process of RCM were analyzed by hydration microcalorimeter,XRD,TG,and SEM-EDS.The experimental results show that four retarders have retarding effect on RCM,among which sodium gluconate and sucrose have significant retarding effect and do not have adverse effect on 28 d strength.Borax can slightly delay the setting time,and sodium hexametaphosphate has a better retarding effect,but they both reduce the 28 d strength.Microcosmic analysis shows that the retarders do not change the type of RCM hydration products,but mainly slow down the rate of hydration reaction through the adsorption and complexation or reaction of Ca^(2+)in the slurry.All the results show that the retarder has no weakening effect on the unconfined compressive strength,water stability and CBR properties of the stabilized subgrade soil based on RCM.展开更多
Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil sta...Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.展开更多
Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-f...Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.展开更多
Background:Soil aggregates are the basic units of soil structure,and their stability is a key indicator of soil quality and capacity to support ecosystem functions.The impacts of various environmental factors on soil ...Background:Soil aggregates are the basic units of soil structure,and their stability is a key indicator of soil quality and capacity to support ecosystem functions.The impacts of various environmental factors on soil aggregates have been widely studied.However,there remains elusive knowledge on the synergistic effects of changing forest stand structure on soil aggregate stability(SAS),particularly in subtropical China where soil erosion remains a critical issue.Methods:We investigated variations in the components of soil humus(HS),including humic acids(HAs),fulvic acids(FAs),and humins(HMs),under pure Chinese fir(Cunninghamia lanceolata)plantation(PP)and multilayered mixed plantation(MP)comprising C.lanceolata,Castanopsis hystrix,and Michelia hedyosperma.The state of soil aggregate stability,was determined by three separate methods,i.e.,dry-sieving,wet-sieving,and the Le Bissonnais.High-throughput sequencing was used to determine the diversity and composition of microbial communities under PP and MP.We then built partial least squares path models(PLS-PM)for assessing the responses of SAS to the variations in soil microorganisms and HS components.Results:The MP stands had significantly greater SAS(P<0.05),higher content of HAs and more rapid organic matter humification within aggregates,than the PP stands.High-throughput sequencing confirmed that the Pielou andα-diversity index values(Chao1 and Shannon)for fungi were all significantly higher under MP than under PP,while no marked difference was found in bacterialα-diversity between the two plantation types.Moreover,there were markedly greater abundance of three bacterial phyla(Verrucomicrobia,Chloroflexi,and Gemmatimonadetes)and three fungal phyla(Ascomycota,Kickxellomycota,and Glomeromycota),and significantly less abundance of two bacterial phyla(Planctomycetes and Firmicutes)and four fungal phyla(Basidiomycota,Mortierellomycota,Mucoromycota,and Rozellomycota)under MP than under PP.The Chloroflexi and Ascomycota phyla appeared to be the primary drivers of soil aggregate distribution.Our findings revealed that the promotion of SAS under MP was mainly driven by increased soil organic matter(SOM)content,which altered bacterial communities and enhanced fungal diversity,thereby increasing HAs content and the rate of organic matter humification.Conclusions:Considering the combined effects of enhanced soil quality,productivity,and relevant economic costs,introducing broadleaved tree species into Chinese fir plantations can be an effective strategy for stabilizing soil structure against erosion in subtropical China.Our study elucidated the controls on variations of SAS in Chinese fir-dominated plantations and demonstrated the benefit of converting pure Chinese fir plantation to multi-layered mixed plantations in increasing soil structural stability and improving site quality.展开更多
This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized s...This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.展开更多
基金Funded by the National Key R&D Program of China (No. 2022YFC3803405)the China State Construction Key Laboratory Project (No. ZJXJ-PT-2022-14)。
文摘This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The impact of SDG components on the strength and durability of solidified soil was analysed through a series of tests,including unconfined compressive strength,water stability coefficient,water absorption rate,drying-wetting cycles,and shrinkage tests.Furthermore,microstructure characteristics were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM).The study shows that the solidified soil has excellent strength and durability when the SDG stabilizer contains 60% GGBGS,10% DG,and 30% CCS.Additionally,increasing the DG content negatively affects the soil's resistance to water.The SDG stabilizer has potential chemical cementitious characteristics and the calcium carbide slag is rich in calcium ions,which undergo an ion exchange reaction with minerals in the soil.These findings offer new ideas for the development of soil stabilizers.
基金Beijing Agricultural Science and Technology Project(2013011202)~~
文摘The research analyzed characters of soil stabilizer and detailed the solidification mechanism.Furthermore,new type soil stabilizer Q2 was used in a base of Beijing Vocational College of Agriculture and a solidified road with length of 250 m,width of 4 m and thickness of 0.25 m were constructed.The road was tested with an agricultural truck and subgrade tolerance to freezing was tested also.It is suggested that new type soil stabilizer would reduce construction cost of road,protect environment,and reduce construction period,with high value of application.
基金supported by the National Natural Science Foundation of China (Nos. 40972185, 41002102)Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 200804910504)
文摘The change in the thickness of water films of special clay particles such as sliding clay, red clay, and expansive clay is an important factor in producing geological disasters and geological environmental damage. In order to reduce the thickness of water films, ionic soil stabilizer （ISS） is used to treat sliding clay, red clay, and expansive clay. Direct shear test of sliding clay and shrinkage, free swell rate, zeta potential, and cation-exchange capacity of red clay and expansive clay are carried out. The results show that as the plastic indexes of special clay soil decrease, the shear strength of sliding clay increases, the shrinkage and free swell rate of red clay and expansive clay decrease, and the thickness of the water film thins after treatment with the ionic soil stabilizer. Therefore, the geological engineering disasters caused by changes in the thickness of water films of special clay can be effectively inhibited.
基金The National Natural Science Foundation of China(No.51108081)
文摘In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental scheme.Three levels o f each factor armconsidered to obtain the change laws o f UCS,in which the binder dosages are8%,10%,and12%;the curing times ae7,14and21d;the gradation nae0.3,0.35and0.4;and the degrees of compaction are95%,97%,and99%.The range analysis clearly indicates that the influence degree o f the four factors on UCS is in such an order:dosage,age,gradation,and degree o f compaction.The variance analysis shows that only the composite soil stabilizer dosage can significantly affect UCS.In road construction,the examination o f composite soil stabilizer dosage and base-course maintenance should be given much more attention to obtain satisfactory base-course strength,compared w ith gradation floating and the change of degree o f compaction.
基金Funded by the National Natural Science Foundation of China(No. 50278007)
文摘A stabilized soil structure formation model was introduced. In order to form compact stabilized soil structure, cementitious hydrates were needed to wrap and bind the soil aggregates. Meanwhile, expansible hydrates were needed to squeeze and fill the pores, especially the pores in the aggregates. The experimental results show that the influences of various chemical characteristic factors of soil on the strength of the stabilized soil are boiled down, for the influence on the concentration of Ca（OH）2 in the pore solution of the stabilized soil, and the amount of CSH generated by cement. Finally an optimization design method is proposed, with which the stabilizer can be designed according to characteristics of soil samples.
基金funded by Science and Technology Program of Qinghai Province of China(2024-SF-129)the National Natural Science Foundation of China(42002283).
文摘The impact mechanism of vegetation on slope soil water infiltration and stability in the loess areas of the northeastern Qinghai-Tibet Plateau remains unclear.Understanding this mechanism is crucial for regional ecological restoration and shallow geological disaster prevention.This study investigated slopes covered by Caragana korshinskii Kom.by employing double-ring infiltration tests to explore the permeability characteristics and influencing factors of root-containing soils and to propose an appropriate infiltration model.Considering the synergistic effects of the canopy and roots,the hydrological response and stability of vegetation-covered slopes under rainfall infiltration conditions were evaluated through numerical simulation analysis.The results revealed that within the main root distribution layer(0-0.5 m),the initial and average infiltration rates and the permeability coefficient of the root-soil composite were significantly higher than those of bare land.Coarse roots with diameters of>5 mm were the key contributors to enhancement of the infiltration capacity.The dry density,fine particle content,and initial water content of the soil around the roots were negatively correlated with the infiltration process.The Horton model effectively reproduced the infiltration process under the canopy and on bare land.The roots significantly accelerated the advance of the slope wetting front during rainfall infiltration,whereas the canopy delayed its onset and progression.The rainfall infiltration process on vegetation-covered slopes was divided into three stages:the equilibrium infiltration stage,optimal infiltration stage beneath the canopy,and secondary equilibrium stage.Vegetation enhances slope stability through coupling of the canopy and root,with an order of canopy-root mode>root mode>bare slope.Under heavy rainfall conditions,the direct contribution of canopy interception to slope stability is limited,and its primary role is to delay the occurrence of instability.During this period,the mechanical effect of roots becomes the dominant mechanism in slope protection.
文摘Unconfined Compressive Strength(UCS)is a key parameter for the assessment of the stability and performance of stabilized soils,yet traditional laboratory testing is both time and resource intensive.In this study,an interpretable machine learning approach to UCS prediction is presented,pairing five models(Random Forest(RF),Gradient Boosting(GB),Extreme Gradient Boosting(XGB),CatBoost,and K-Nearest Neighbors(KNN))with SHapley Additive exPlanations(SHAP)for enhanced interpretability and to guide feature removal.A complete dataset of 12 geotechnical and chemical parameters,i.e.,Atterberg limits,compaction properties,stabilizer chemistry,dosage,curing time,was used to train and test the models.R2,RMSE,MSE,and MAE were used to assess performance.Initial results with all 12 features indicated that boosting-based models(GB,XGB,CatBoost)exhibited the highest predictive accuracy(R^(2)=0.93)with satisfactory generalization on test data,followed by RF and KNN.SHAP analysis consistently picked CaO content,curing time,stabilizer dosage,and compaction parameters as the most important features,aligning with established soil stabilization mechanisms.Models were then re-trained on the top 8 and top 5 SHAP-ranked features.Interestingly,GB,XGB,and CatBoost maintained comparable accuracy with reduced input sets,while RF was moderately sensitive and KNN was somewhat better owing to reduced dimensionality.The findings confirm that feature reduction through SHAP enables cost-effective UCS prediction through the reduction of laboratory test requirements without significant accuracy loss.The suggested hybrid approach offers an explainable,interpretable,and cost-effective tool for geotechnical engineering practice.
基金supported by the National Key Research and Development Program of China(2024YFF1306305)the Inner Mongolia Autonomous Region Natural Science Foundation Project(2025QN03106)+1 种基金the Research Start-up Project for the Introduction of High-level and Outstanding Doctoral Talent at Inner Mongolia Agricultural University(NDYB2024-42)the National Natural Science Foundation of China(42201012).
文摘Global grassland degradation necessitates the identification of sustainable grazing management strategies.In semi-arid regions,grazing exclusion(GE),cold-season grazing(CG),and free grazing(FG)represent common practices in grassland ecosystems,yet the long-term ecological consequences of these patterns on plant community structure and soil aggregate stability remain inadequately elucidated.In this study,we evaluated the effects of GE,CG,and FG on soil organic carbon,soil water content,soil bulk density,soil aggregates,and vegetation indicators in Xilamuren steppe,a semi-arid grassland in northern China through field sampling and laboratory analyses in 2024.Our findings revealed that,compared to CG and FG,GE significantly enhanced aboveground and belowground biomass,species diversity,and soil physical-chemical properties in the 0–30 cm layer.The dominant plant species in GE and CG sites were Stipa krylovii,Leymus chinensis,and Agropyron cristatum,whereas Stipa krylovii,Artemisia frigida,and Leymus chinensis were predominant in FG site.Different grazing patterns led to distinct soil aggregate distributions,with>2.00 and<0.25 mm aggregates exhibiting the highest content in different soil layers depending on the grazing patterns.All grazing management strategies significantly improved soil aggregate stability,with the overall stability following the order:GE>CG>FG.Furthermore,random forest modeling identified plant species diversity,plant growth traits,and grazing patterns as the primary determinants of soil aggregate stability.Collectively,these results offer valuable insights into the sustainable management and ecological restoration of semi-arid grasslands under different grazing pressures.
文摘This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.
文摘We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing alkali-activated sewage sludge(AASS)as a binder for stabilizing the clayey soil.Sewage sludge(SS)in varying proportions of 1.5%,2%,2.5%,3.5%,and 4.5%was utilized to prepare geopolymer binders using sodium and potassium-based alkali activators.Furthermore,unconfined compressive strength(UCS)and direct shear tests were conducted to examine the strength development of clayey soil stabilized with AASS.While the study presented some intriguing results,we have identified critical concerns regarding(i)the selection of SS as a precursor for alkali activation,(ii)technical inconsistencies associated with the compaction characteristics and microstructural analysis,and(iii)the feasibility of the proposed methodology for practical applications.Through our discussion,we seek to highlight these issues and provide constructive feedback to advance the understanding of alkali activation processes and their implications for soil stabilization.
基金financial support for the research provided by the National Natural Science Foundation of China(No.42107350)the National Key Research,Development Program of China(No.2023YFD1902801)the Central Government Guides the Development of Local Science and Technology Project,Grant/Award Number:Guike ZY21195022。
文摘A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a basic understanding of aggregate formation and stabilization,the functional relationship between aggregate stability and erosion resistance under extended sugarcane monoculture remains inadequately characterized.We employed an integrated methodology combining dry/wet sieving,the Le Bissonnais method and scanning electron microscopy to quantitatively evaluate the soil aggregate stability and erosion resistance across six distinct cultivation chrono-sequences(3–32 years)and two soil depths(0–15 cm and 15–30 cm)in the sugarcane cultivation area of Qingshui Village,Wuxuan County,Guangxi Zhuang Autonomous Region,China,aiming at providing insights for developing soil conservation strategies in sugarcane cultivation systems.The results reveal three core findings.First,planting years significantly influence the proportions of soil aggregates with varying particle sizes.Under the treatments with Le Bissonais methods,the mean weight diameter(MWD)under fast wetting,disturbance after pre-wetting,and slow wetting decrease with increasing planting years,while the relative dissipation index,relative mechanical fragmentation index,and erodibility factor(K)exhibit varying degrees of change,indicating progressive soil structural degradation and increased erosion susceptibility.Second,long-term sugarcane monocropping leads to declining soil organic carbon,liquid limit,plastic limit,and clay content,likely due to factors such as soil-forming materials and rainfall.Concurrently,the increased sand content and porosity weaken interparticle bonding and reducing aggregate stability over time.Third,correlation analysis demonstrates that MWD and geometric mean diameter(GMD)under disturbance after pre-wetting and slow wetting treatments show strong positive correlations with soil organic carbon,p H,clay content,liquid limit,and plastic limit but negative correlations with sand content,total porosity,and capillary porosity.Furthermore,K is significantly negatively correlated with soil physicochemical properties as well as GMD and MWD.These results help us understand the mechanism of aggregate stability variation in sugarcane-cultivated red soils and support the development of soil conservation strategies for sustaining sugarcane productivity in subtropical regions.
基金supported by the National Natural Science Foundation of China(NO.32201626)the Key Research and Development Program of Jiangxi Province(20223BBG74S01,20223BBG71013).
文摘In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear strength are indicators that reflect soil resistance to erosion and its ability to prevent shallow landslides,respectively.However,limited research has focused on the response of soil aggregate stability and shear strength to reforestation.We selected three types of reforestations(Phyllostachys edulis forest,Cunninghamia lanceolata(Lamb.)Hook.forest,Citrus sinensis(L.)Osbeck.orchard),a natural forest(mixed coniferous and broadleaf forests),and a fallow land as study plots,and measured root traits,and soil physicochemical traits,i.e.,pH,soil organic matter(SOC),Soil water content(SWC),soil bulk density(BD),soil cohesion(c),soil internal friction angle(φ)and analyzed their multiple interactions.The soil aggregate stability traits,refer to the mean weight diameter(MWD)and geometric mean diameter(GMD),exhibited a significant increase in reforested plots,approximately 200%compared to fallow land and 50%compared to natural forests.For soil shear strength the values were approximately 20%higher than in fallow land and approximately 10%lower than in natural forests.Soil aggregate stability and soil shear strength did not exhibit a significant positive correlation across all plots,and the underlying drivers of these traits were variable.For instance,in natural forest and timber stands,soil aggregate stability was mainly influenced by soil organic carbon,while soil shear strength was primarily affected by root length density.In economic forest,aggregate stability and shear strength are mainly affected by organic carbon.Overall,we found that vegetation restoration enhances soil erosion resistance,however,the primary drivers for the improvement of aggregate stability(soil organic carbon)and shear strength(root length density)are different.Therefore,in future benefit assessments of vegetation restoration projects aimed at soil erosion control,different indicators should be considered based on specific conditions.
文摘The sustainable geotechnical approach for addressing the challenges associated with clayey soils at construction sites involves the modification of these soils’mechanical and chemical characteristics using soil enhancement methods.The present study investigates the coupling effect of sandstone slurry waste(SSW)and calcium carbonate nanoparticle(CCN)as potential stabilizers to enhance the characteristics of clayey soil.A comprehensive investigation was conducted using compaction tests,plasticity index(PI)tests,California bearing ratio(CBR)tests,unconfined compressive strength(UCS)tests,and microstructural analyses of clayey soil,SSW and SSW-CCN-treated clay samples containing 5%,10%,15%,20%,25%,30%,and 35%SSW and 0.3%,0.6%,0.9%,1.2%,and 1.5%CCN mixed with clayey soil in different combinations of clay,SSW,and CCN.The findings reveal that incorporating 25%SSW with 0.9%CCN into clay soil results in an increase in the UCS from 132.2 kPa for untreated clayey soil without curing to 263 kPa after a 28-d curing period.Similarly,a rising trend in CBR results is observed up to 25%SSW addition in clay soil and up to 0.9%CCN addition in SSW-clay mixture.Initially,notable enhancements in UCS were attributed to a denser soil structure,followed by the formation of calcium–silicate–hydrate(CSH)gel,which intensified with prolonged curing.Gel patches were detected by scanning electron microscopy(SEM)in addition to particle aggregation.The results obtained from thermogravimetric analysis,Fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)supported the presence of hydration products such as CSH.The experimental study indicates that SSW,in combination with CCN,offers a sustainable alternative to traditional soil stabilizers.
基金The National Key Technology R&D Program of China during the 12th Five Year Plan Period(No.2011BAD31B05)the National Natural Science Foundation of China(No.41371276)+1 种基金the National Science and Technology Major Project of China(No.2009ZX07212-002-003-02)the Knowledge Innovation Project of theInstitute of Soil and Water Conservation,CAS&MWR(No.A315021304)
文摘A plastic mixture construction technology using MBER （material becoming earth into rock） soil stabilizer is introduced and the water quality of a solidified soil cistern using the technology is analyzed. Rainwater was harvested in July, 2012. Water quality of runoff and cistern water after storage was measured, including turbidity, chemical oxygen demand （COD）, total nitrogen, nitrate, and ammonia. Results show that pollutant concentrations in runoff decreased with time, indicating that runoff in the early time should be removed. Nitrate concentrations in cistern water increased after storage, while the remaining parameters decreased. Measured pollutant concentrations did not exceed the limit according to the standard for drinking water in China. It can be concluded that the solidified soil cistern with plastic mixture construction technology can provide available water for domestic use.
基金supported by National Natural Science Foundation of China(Grant No.42201080)Young Scientific and Technological Talents Program of Shaanxi Province(Grant No.2025ZC-KJXX-57)Special Scientific Research Program of the Shaanxi Provincial Department of Education(Grant No.21JK0967)。
文摘Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.
基金Funded by the Shandong Province Key R&D Program(Major Technological Innovation Project(Nos.2023ZLGX01 and 2021CXGC010301)the Youth Project of National Natural Science Foundation(No.52309136)+1 种基金the Competitive Innovation Platform Project of Shandong Province(No.2023CXPT-080)the Postdoctoral Innovation Project(No.SDCX-ZG-202203037)。
文摘To improve the applicability of red mud in subgrade construction,we studied the effects of four traditional retarders,including borax,sodium hexametaphosphate,sodium gluconate,and sucrose,on the setting time,mechanical properties and soil solidification of red mud-based subgrade engineered cementitious material(RCM).The mechanisms of the retarders on the hydration process of RCM were analyzed by hydration microcalorimeter,XRD,TG,and SEM-EDS.The experimental results show that four retarders have retarding effect on RCM,among which sodium gluconate and sucrose have significant retarding effect and do not have adverse effect on 28 d strength.Borax can slightly delay the setting time,and sodium hexametaphosphate has a better retarding effect,but they both reduce the 28 d strength.Microcosmic analysis shows that the retarders do not change the type of RCM hydration products,but mainly slow down the rate of hydration reaction through the adsorption and complexation or reaction of Ca^(2+)in the slurry.All the results show that the retarder has no weakening effect on the unconfined compressive strength,water stability and CBR properties of the stabilized subgrade soil based on RCM.
基金Project supported by the National Natural Science Foundation of China (No.40371059).
文摘Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.
基金supported by Chem Concrete Pty.Ltd.Australia,Abadgaran Negin Jonoobshargh Company(ANJ Co.),Iran(Grant No.118/3C-1399)。
文摘Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.
基金the National Natural Science Foundation of China(Nos.31960240 and 32171755)the Guangxi Natural Science Foundation(No.2019GXNSFAA185023)the Scientific Research Capacity Building Project for Youyiguan Forest Ecosystem Observation and Research Station of Guangxi under Grant No.2203513003。
文摘Background:Soil aggregates are the basic units of soil structure,and their stability is a key indicator of soil quality and capacity to support ecosystem functions.The impacts of various environmental factors on soil aggregates have been widely studied.However,there remains elusive knowledge on the synergistic effects of changing forest stand structure on soil aggregate stability(SAS),particularly in subtropical China where soil erosion remains a critical issue.Methods:We investigated variations in the components of soil humus(HS),including humic acids(HAs),fulvic acids(FAs),and humins(HMs),under pure Chinese fir(Cunninghamia lanceolata)plantation(PP)and multilayered mixed plantation(MP)comprising C.lanceolata,Castanopsis hystrix,and Michelia hedyosperma.The state of soil aggregate stability,was determined by three separate methods,i.e.,dry-sieving,wet-sieving,and the Le Bissonnais.High-throughput sequencing was used to determine the diversity and composition of microbial communities under PP and MP.We then built partial least squares path models(PLS-PM)for assessing the responses of SAS to the variations in soil microorganisms and HS components.Results:The MP stands had significantly greater SAS(P<0.05),higher content of HAs and more rapid organic matter humification within aggregates,than the PP stands.High-throughput sequencing confirmed that the Pielou andα-diversity index values(Chao1 and Shannon)for fungi were all significantly higher under MP than under PP,while no marked difference was found in bacterialα-diversity between the two plantation types.Moreover,there were markedly greater abundance of three bacterial phyla(Verrucomicrobia,Chloroflexi,and Gemmatimonadetes)and three fungal phyla(Ascomycota,Kickxellomycota,and Glomeromycota),and significantly less abundance of two bacterial phyla(Planctomycetes and Firmicutes)and four fungal phyla(Basidiomycota,Mortierellomycota,Mucoromycota,and Rozellomycota)under MP than under PP.The Chloroflexi and Ascomycota phyla appeared to be the primary drivers of soil aggregate distribution.Our findings revealed that the promotion of SAS under MP was mainly driven by increased soil organic matter(SOM)content,which altered bacterial communities and enhanced fungal diversity,thereby increasing HAs content and the rate of organic matter humification.Conclusions:Considering the combined effects of enhanced soil quality,productivity,and relevant economic costs,introducing broadleaved tree species into Chinese fir plantations can be an effective strategy for stabilizing soil structure against erosion in subtropical China.Our study elucidated the controls on variations of SAS in Chinese fir-dominated plantations and demonstrated the benefit of converting pure Chinese fir plantation to multi-layered mixed plantations in increasing soil structural stability and improving site quality.
基金the China Postdoctoral Science Foundation(Grant Nos.2016M600396 and 2017T100355)the Fundamental Research Funds for the Central Universities of China(Grant No.B200204001)Jiangsu Natural Resources Science and Technology Fund(Grant No.KJXM2019025)are also acknowledged.
文摘This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.
