Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion di...Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion discrete model that is capable of dynamically assessing the effect of cracking on moisture diffusion and allowing moisture to be discontinuous on both sides of the cracks.Then,the parametric analysis of the moisture exchange coefficient in the 3D moisture diffusion discrete model is carried out for moisture diffusion in continuous media,and the selection criterion of the moisture exchange coefficient for the unbroken cohesive element is given.Subsequently,an example of moisture migration in a medium with one crack is provided to illustrate the crack hindering effect on moisture migration.Finally,combining the 3D moisture diffusion discrete model with the finite-discrete element method(FDEM),the moisture diffusion-fracture coupling model is built to study the desiccation cracking in a strip soil and the crack pattern of a rectangular soil.The evolution of crack area and volume with moisture content is quantitatively analyzed.The modeling number and average width of cracks in the strip soil show a good consistency with the experimental results,and the crack pattern of the rectangular soil matches well with the existing numerical results,validating the coupled moisture diffusion-fracture model.Additionally,the parametric study of soil desiccation cracking is performed.The developed model offers a powerful tool for exploring soil desiccation cracking.展开更多
In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoe...In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoenvironmental engineering.Despite the growing utilization of biochar as a sustainable soil amendment,there remains a lack of in-depth understanding of biocharewateresoil interactions,as well as its impact on soil desiccation cracking behavior.To address this gap,this study investigated the influence and mechanism of woody biochar dosages and particle sizes on the cracking behavior of three typical clayey soils in subtropical regions in China,namely Pukou expansive soil(PKE),Xiashu soil(XS),and Zhongshan lateritic soil(ZSL).The quantitative analysis of crack images revealed that the use of biochar was not consistently effective in preventing soil cracking.The application of biochar reduced the crack ratio in PKE and XS by up to 24.03%and 53.89%,respectively.In contrast,ZSL exhibited a 74.57%increase in crack ratio with the addition of 10%biochar.This influence can be further enhanced by increasing the dosage and reducing the particle size of biochar.The microstructural analysis demonstrated that biochar exerts an inhibitory effect on PKE and XS primarily through direct replacement,direct barrier,and indirect physical mechanisms.Moreover,an indirect chemical effect between biochar and clay particles was proposed to explain the exacerbated cracking observed in biochar-amended ZSL.To effectively utilize biochar for soil cracking mitigation in subtropical regions,it is essential to evaluate the initial mineral composition and cation type of the soil.展开更多
Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracki...Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracking behavior through a numerous small-sample experiments.However,experimental studies alone cannot accurately describe soil cracking behavior.In this study,we firstly propose a modeling framework for predicting the surface crack ratio of soil desiccation cracking based on machine learning and interpretable analysis.The framework utilizes 1040 sets of soil cracking experimental data and employs random forest(RF),extreme gradient boosting(XGBoost),and artificialneural network(ANN)models to predict the surface crack ratio of soil desiccation cracking.To clarify the influenceof input features on soil cracking behavior,feature importance and Shapley additive explanations(SHAP)are applied for interpretability analysis.The results reveal that ensemble methods(RF and XGBoost)provide better predictive performance than the deep learning model(ANN).The feature importance analysis shows that soil desiccation cracking is primarily influencedby initial water content,plasticity index,finalwater content,liquid limit,sand content,clay content and thickness.Moreover,SHAP-based interpretability analysis further explores how soil cracking responds to various input variables.This study provides new insight into the evolution of soil cracking behavior,enhancing the understanding of its physical mechanisms and facilitating the assessment of potential regional development of soil desiccation cracking.展开更多
Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shr...Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shrinkage and cracking,which can significantly affect its engineering properties and ultimately jeopardize engineering safety.This paper presents a desiccation cracking test of fine-grained coral soil,with a particular focus on the thickness effect.The study involved measuring the water content and recording the evolution of desiccation cracking.Advanced image processing technology is employed to analyze the variations in crack parameters,clod parameters,fractal dimensions,frequency distributions,and desiccation cracking propagation velocities of fine-grained coral soil.Furthermore,the dynamic evolution of desiccation cracking under the influence of layer thickness is analyzed.A comprehensive crack evolution model is proposed,encompassing both top-down and bottom-up crack propagation,as well as internal tensile cracking.This work introduces novel metrics for the propagation velocity of the total crack area,the characteristic propagation velocities of desiccation cracks,and the acceleration of crack propagation.Through data fitting,theoretical formulas for soil water evaporation,propagation velocities of desiccation cracks,and crack propagation acceleration are derived,laying a foundation for future soil cracking theories.展开更多
The effects of desiccation cracking in clay soils on geotechnical constructions are substantial.This study investigates the viability of utilizing Enzyme-induced calcite precipitation(EICP),a bio inspired approach,as ...The effects of desiccation cracking in clay soils on geotechnical constructions are substantial.This study investigates the viability of utilizing Enzyme-induced calcite precipitation(EICP),a bio inspired approach,as a potential solution for addressing desiccation cracking in fine-grain soils.For the EICP technique,crude soybean extract is employed for the purpose of urea hydrolysis.Multiple fluid samples,including a control sample,a cementation solution containing 1 M urea,0.675 M CaCl_(2),and 4 g/L milk,along with various concentrations of enzyme solutions(3-80 g/L),were tested for the study.To evaluate the surface cracking patterns,the method involved constant monitoring and photo recording using a high-resolution camera aided by image processing software.The results showed that fine-grain soils improved from increased calcite precipitation and decreased desiccation cracking intensity when the EICP method was used.Cementation and enzyme solution with low concentrations(3 g/L and 10 g/L)had similar effects on crack remediation,suggesting a modest influence.In contrast to the sample treated with water,the crack network remained unaltered in this case.CaCO3 precipitation within the void area kept the crack network in place even as the void thickness decreased at increasing enzyme concentrations(30 g/L,50 g/L,and 80 g/L).Wetting and drying cycles were found to decrease the crack ratio,crack width,and crack length in the EICP-treated sample,particularly under higher concentrations of urease enzyme.Lower enzyme concentrations of 3 g/L and 10 g/L have minimal impact on crack remediation but effectively inhibit new crack formation.Furthermore,higher enzyme concentrations result in calcium carbonate precipitates,forming a soil crust and increasing surface roughness.The study aims to enhance understanding of the EICP methodology and to provide novel perspectives on potential uses for soil enhancement.展开更多
The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporat...The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporation,while a digital camera was utilized to capture the initiation and progression of soil surface cracking.Results indicate that in the early drying process,the rate of evapotranspiration in vegetated soil correlates positively with leaf biomass.For soil samples with the same layer thickness,the constant rate stage duration is consistently shorter in vegetated soil samples than in their bare soil counterparts.As the layer thickness increases,both vegetated and bare soil samples crack at higher water content.However,vegetated soil samples crack at lower water content than their bare soil counterparts.Vegetation significantly reduces the soil surface crack ratio and improves the soil crack resistance.The crack reduction ratio is positively correlated with both root weight and length density.In thicker vegetated soil layers,the final surface crack length noticeably declines.展开更多
Drought-induced desiccation cracking can trigger several weakening mechanisms in surface soils,potentially precipitating instability and failure of slopes and earthen structures.To investigate the potential applicatio...Drought-induced desiccation cracking can trigger several weakening mechanisms in surface soils,potentially precipitating instability and failure of slopes and earthen structures.To investigate the potential application of distributed fibre optical sensing(DFOS)based on optical frequency domain reflectometry(OFDR)technology in characterizing the twodimensional(2D)desiccation cracking processes of surface soils,a comprehensive test device is utilized to conduct soil evaporation tests,continuously record water content changes,desiccation cracking evolution,and FO sensing strain status.A deep learning-based quantitative analysis method is employed to meticulously examine the relationship between 2D cracking geometric parameters and strain status.The comprehensive analysis not only reveals the mutual feedback response mechanism between the strain status and the soil evaporation-shrinkage-cracking processes,but also clarifies the early detection distance of OFDR technology for 2D desiccation cracking.Specifically,OFDR technology can detect the propagation of horizontal desiccation cracks up to 23 mm in advance with a strain measurement accuracy of 1με.To address the spatial continuity issue in OFDR sensing strain data,an innovative high-resolution characterization framework is proposed by combining the finite element method(FEM)and OFDR technology,referred to as the FEM-OFDR framework.Comparative results indicate that the proposed FEM significantly surpasses both the kriging and radial basis function(RBF)methods in inferring missing OFDR sensing strain data.Notably,during the drying process,reaching a critical water content causes the local decoupling between the uncracked clods and the substrate,resulting in a decreasing trend in the sensing strain at the crack position.This study provides crucial technical means and theoretical support for a deeper understanding of the mechanisms driving 2D desiccation-induced shrinkage and cracking in surface soils.展开更多
Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking.This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey so...Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking.This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils.To validate the feasibility and efficacy of the proposed approach,direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents.Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance.During this period,the effects of W-OH treatment concentration and water content on tensile properties,soil suction and microstructure were investigated.The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil,which not only effectively enhances the tensile strength and failure displacement,but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior.The suction measurements and mercury intrusion porosimetry(MIP)tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores.Combined with the microstructural analysis,it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles.Moreover,desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking.With the increase of W-OH treatment concentration,the surface crack ratio and total crack length are significantly reduced.This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance.展开更多
Both cracks in clay liner and the complex composition of landfill leachate might have effects on the hydraulic conductivity of a compacted clay liner. In this study, the hydraulic conductivities of natural clay and be...Both cracks in clay liner and the complex composition of landfill leachate might have effects on the hydraulic conductivity of a compacted clay liner. In this study, the hydraulic conductivities of natural clay and bentonite-modified clay with and without desiccation cracks were measured, respectively, using three types of liquids as permeating liquid： 2 500 mg/L acetic acid solution, 0.5 mol/L CaCl2 solution, and tap water. When tap water was adopted as the permeating liquid, desiccation cracks resulted in increases in the average value of hydraulic conductivity： a 25-fold increase for the natural clay and a 5.7-fold increase for the bentonite-modified clay. It was also found out that the strong selfhealing capability of bentonite helped to reduce the adverse impact of cracks on hydraulic performance. In contrast to tap water, simulated leachates（acetic acid and CaCl2 solutions） show no adverse effect on the hydraulic conductivities of natural and bentonite-modified clays. It is concluded that desiccation cracks and bentonite have more significant effects on hydraulic performance than simulated leachates.展开更多
Dry-wet cycle is a key factor in surface weathering of earthen heritage,which remains insufficiently explained.It involves the interaction of humidity,stress,and damage.Using the RFPA(realistic failure process analysi...Dry-wet cycle is a key factor in surface weathering of earthen heritage,which remains insufficiently explained.It involves the interaction of humidity,stress,and damage.Using the RFPA(realistic failure process analysis)numerical method,this study reproduced the processes of humidity diffusion,deformation,stress,and damage evolution under dry-wet cycles in the soil site of Suoyang City,China.The numerical results indicate that the drying phase following rainfall has the most significant deteriorative impact on the earthen heritage.The evaporation of surface moisture during this phase causes volume shrinkage,which in turn generates tensile stress and leads to the formation of numerous desiccation cracks.Desiccation cracks provide channels for moisture diffusion,which further exacerbates generation of the cracks,leading to a mutual promotion between the two phenomena.Furthermore,during the wetting phase,the model elements undergo hygroscopic expansion,resulting in a slight increase in strain and displacement.Previously formed cracks may exhibit temporary narrowing or closure,but will revert during the subsequent drying phase.Ultimately,the overall displacement increases with the number of dry-wet cycles.The findings provide a theoretical foundation for protection against surface weathering and other damage in earthen heritage in arid regions.展开更多
The Songnen Plain has a typical soda-saline soil, which often shrinks and cracks under natural conditions during water evaporation. This study aims to analyze the relationships between the crack characteristics and th...The Songnen Plain has a typical soda-saline soil, which often shrinks and cracks under natural conditions during water evaporation. This study aims to analyze the relationships between the crack characteristics and the soil properties of soda-saline soils quantitatively, and attempts to establish prediction models for the main soil properties of soda-saline soils based on the results. In order to achieve these objectives, a desiccation cracking test was conducted using 17 soil specimens with different salinity levels under controlled laboratory conditions. Correlation analysis was then performed between the crack characteristics and the soil properties. The results indicate that the crack characteristics can well represent the surface appearances of cracked soils, they also can well distinguish the salinity levels of soda-saline soils while the clay contents and mineralogical compositions of soils are stable. Among the crack characteristics, crack length has the best relationships with the salinity levels of soda-saline soils. Specifically, the crack length has high correlation(R2 > 0.87) with the electrical conductivity(EC), Na+, CO32– and the salinity, it also has reasonable relationship(R2 > 0.68) with HCO3–, this indicates crack length can be well used for the prediction of these properties of soda-saline soils.展开更多
Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of ei...Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of either permafrost or seasonal frost during the Late Pleistocene and early Holocene. Wedges of about 1 m in depth form polygonal nets of 2-3 m in diameter(type B). They contrast with wedges of 3-4 m in depth that form polygons of 10-15 m in diameter(type A).This review focuses upon the highly variable size of the inferred polygon nets and discusses the problem of differentiating between seasonally and perennially frozen ground, or between seasonal frost and permafrost.展开更多
In continental and oceanic conditions, clay-rich deposits are characterised by the development of polygonal fracture systems（PFS）. PFS can increase the vertical permeability of clay-rich deposits（mean permeability ...In continental and oceanic conditions, clay-rich deposits are characterised by the development of polygonal fracture systems（PFS）. PFS can increase the vertical permeability of clay-rich deposits（mean permeability ≤10-16 m2） and are pathways for fluids. On continents, the width of PFS ranges from centimeters to hundreds of meters, while in oceanic contexts they are up to a few kilometers large. These structures are linked to water-solid separation during deposition, consolidation and complete fluid squeeze of the clay horizon. During the last few decades, modeling of melt migration in partially molten plastic rocks led to rigorous quantifications of two-phase flows with a particular emphasis on 2D and 3D induced flow structures. The numerical modeling shows that the melt migrates on distances almost equal to a few times the compaction length L that depends on permeability and viscosity. Consequently, polygonal structures in partially molten plastic rocks are resulted from the melt-rock separation and their sizes are proportional to L. Applying these results to fluid-solid separation in clay-rich horizons, we show that（1） centimetric to kilometric PFS are resulted from the dramatic increase of L during compaction and（2）, this process involves agglomerates with 100 μm to 1 mm size.展开更多
The phenomena of shrinkage and swelling of clay induce damage to housing structures every year. Precipitation, climatic changes and drought are the cause of wall cracks due to subsidence or swelling of the supporting ...The phenomena of shrinkage and swelling of clay induce damage to housing structures every year. Precipitation, climatic changes and drought are the cause of wall cracks due to subsidence or swelling of the supporting soil. This movement alters the balance between the soil and the structures. To explain this defection, the soil is made up of three elements: the solid, the liquid and the gas. Sometimes in a natural way or following a human intervention, one of these elements undergoes an abnormal variation that causes the loss of the balance between land and works. It is in this sense that this article deals on the one hand with the factors of predisposition and triggering of the phenomena of shrinkage-swelling of the clay soils of Diamniadio and on the other hand, the factors of aggravation linked to the lithological heterogeneity and the variation in the thickness of the layers susceptible to shrinkage-swelling. The studies carried out have enabled a deeper understanding of the behavior of expansive soils following their interactions with climate, vegetation, hydrology, hydrogeology, constructions among others, but also the influence of lateral and vertical variations of fine soil facies.展开更多
Crack patterns observed in nature have attracted the interest of researchers in various fields, and the mechanism of the pattern formation has been investigated. However, the phenomenon is very complicated, and many f...Crack patterns observed in nature have attracted the interest of researchers in various fields, and the mechanism of the pattern formation has been investigated. However, the phenomenon is very complicated, and many factors affect the process. Therefore, we are motivated to construct a general simulation code with a simple algorithm. In this study, crack pattern formation due to shrinkage caused by the drying of a wet material was simulated. The process was simplified as follows: tensile force is generated in the model, and a crack is generated when the tension exceeds a critical value. The tensile forces in the x and y directions are independently evaluated. A crack propagates perpendicular to the tension until it reaches another crack or a boundary. Based on this modeling, simulations with a two-dimensional square domain were performed. Consequently, a cross-divided pattern was generated. Assuming zigzag crack propagation, more realistic patterns were obtained. The effects of the boundary and domain size were also considered, and various characteristic patterns were obtained. Furthermore, the orientation dependency was simulated, and 45˚ declined patterns and rectangularly divided patterns were generated. The model presented in this study is very simplified and is expected to be applicable to various objects.展开更多
Biochar is a carbon-rich material obtained after thermochemical conversion of biomass under no oxygen environment.The effect of biochar amendment on soil properties,such as water retention,infiltration and desiccation...Biochar is a carbon-rich material obtained after thermochemical conversion of biomass under no oxygen environment.The effect of biochar amendment on soil properties,such as water retention,infiltration and desiccation crack potential was studied in the recent years.However,the effect of biochar or feedstock type on these properties is not explicit.This study investigates the effect of two different(in terms of feedstock)types of biochar on the water retention,infiltration and desiccation crack-ing behavior of compacted silty sand.Water retention characteristics,infiltration rate and the progression of desiccation cracks were measured after compacting soil amended with 5-10%(w/w)biochar produced from water hyacinth(WHB)and mesquite.Measurements were also taken for an unpyrolyzed material coir pith(CP,sourced from coconut husk)-amended soil for comparing the results of biochar-amended soil.The results show that the amendment of 5%to 10%biochar increased the maximum water holding capacity(θs),air entry value(AEV)and water content at 1500 kPa(θ1500)of the soil,whereas decreased the infiltration rate and peak crack intensity factor(CIF)of the soil.Moreover,the application of CP increased the infiltration rate.The amendment of WHB showed the highest increment in AEV andθ1500 and the highest decrement in infiltration rate and CIF compared to the other amendments.Based on the results,it is advisable to use the WHB-amended soil in bioengineered structures that could promote the growth of vegetation by higher water retention and could reduce the potential of leachate formation by decreasing water infiltration and desiccation crack potential.展开更多
基金supported by the State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering(Grant No.SKLGDUEK2206)National Natural Science Foundation of China(Grant No.11872340).
文摘Soil desiccation cracking is a common phenomenon on the earth surface.Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil.This work develops a novel 3D moisture diffusion discrete model that is capable of dynamically assessing the effect of cracking on moisture diffusion and allowing moisture to be discontinuous on both sides of the cracks.Then,the parametric analysis of the moisture exchange coefficient in the 3D moisture diffusion discrete model is carried out for moisture diffusion in continuous media,and the selection criterion of the moisture exchange coefficient for the unbroken cohesive element is given.Subsequently,an example of moisture migration in a medium with one crack is provided to illustrate the crack hindering effect on moisture migration.Finally,combining the 3D moisture diffusion discrete model with the finite-discrete element method(FDEM),the moisture diffusion-fracture coupling model is built to study the desiccation cracking in a strip soil and the crack pattern of a rectangular soil.The evolution of crack area and volume with moisture content is quantitatively analyzed.The modeling number and average width of cracks in the strip soil show a good consistency with the experimental results,and the crack pattern of the rectangular soil matches well with the existing numerical results,validating the coupled moisture diffusion-fracture model.Additionally,the parametric study of soil desiccation cracking is performed.The developed model offers a powerful tool for exploring soil desiccation cracking.
基金supported by the National Natural Science Foundation of China(Grant No.42277124)the National Key Research&Development Program of China(Grant No.2020YFC1808004)the Jiangsu Province 333 Talents Youth Talent Support Project.
文摘In subtropical regions,soil desiccation cracking often exerts a significant impact on the interactions between soil water and the atmosphere,making it a subject of great interest in the fields of geotechnical and geoenvironmental engineering.Despite the growing utilization of biochar as a sustainable soil amendment,there remains a lack of in-depth understanding of biocharewateresoil interactions,as well as its impact on soil desiccation cracking behavior.To address this gap,this study investigated the influence and mechanism of woody biochar dosages and particle sizes on the cracking behavior of three typical clayey soils in subtropical regions in China,namely Pukou expansive soil(PKE),Xiashu soil(XS),and Zhongshan lateritic soil(ZSL).The quantitative analysis of crack images revealed that the use of biochar was not consistently effective in preventing soil cracking.The application of biochar reduced the crack ratio in PKE and XS by up to 24.03%and 53.89%,respectively.In contrast,ZSL exhibited a 74.57%increase in crack ratio with the addition of 10%biochar.This influence can be further enhanced by increasing the dosage and reducing the particle size of biochar.The microstructural analysis demonstrated that biochar exerts an inhibitory effect on PKE and XS primarily through direct replacement,direct barrier,and indirect physical mechanisms.Moreover,an indirect chemical effect between biochar and clay particles was proposed to explain the exacerbated cracking observed in biochar-amended ZSL.To effectively utilize biochar for soil cracking mitigation in subtropical regions,it is essential to evaluate the initial mineral composition and cation type of the soil.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFC3707900 and 2024YFC3012700)the National Natural Science Foundation of China(Grant No.42230710).
文摘Soil desiccation cracking is ubiquitous in nature and has significantpotential impacts on the engineering geological properties of soils.Previous studies have extensively examined various factors affecting soil cracking behavior through a numerous small-sample experiments.However,experimental studies alone cannot accurately describe soil cracking behavior.In this study,we firstly propose a modeling framework for predicting the surface crack ratio of soil desiccation cracking based on machine learning and interpretable analysis.The framework utilizes 1040 sets of soil cracking experimental data and employs random forest(RF),extreme gradient boosting(XGBoost),and artificialneural network(ANN)models to predict the surface crack ratio of soil desiccation cracking.To clarify the influenceof input features on soil cracking behavior,feature importance and Shapley additive explanations(SHAP)are applied for interpretability analysis.The results reveal that ensemble methods(RF and XGBoost)provide better predictive performance than the deep learning model(ANN).The feature importance analysis shows that soil desiccation cracking is primarily influencedby initial water content,plasticity index,finalwater content,liquid limit,sand content,clay content and thickness.Moreover,SHAP-based interpretability analysis further explores how soil cracking responds to various input variables.This study provides new insight into the evolution of soil cracking behavior,enhancing the understanding of its physical mechanisms and facilitating the assessment of potential regional development of soil desiccation cracking.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2022CDJQY-012)the Innovation Group Science Foundation of the Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyj-cxttX0003).
文摘Coralline soils,specialized materials found extensively in the South China Sea,are playing an increasingly vital role in engineering projects.However,like most terrigenous soils,fine-grained coral soil is prone to shrinkage and cracking,which can significantly affect its engineering properties and ultimately jeopardize engineering safety.This paper presents a desiccation cracking test of fine-grained coral soil,with a particular focus on the thickness effect.The study involved measuring the water content and recording the evolution of desiccation cracking.Advanced image processing technology is employed to analyze the variations in crack parameters,clod parameters,fractal dimensions,frequency distributions,and desiccation cracking propagation velocities of fine-grained coral soil.Furthermore,the dynamic evolution of desiccation cracking under the influence of layer thickness is analyzed.A comprehensive crack evolution model is proposed,encompassing both top-down and bottom-up crack propagation,as well as internal tensile cracking.This work introduces novel metrics for the propagation velocity of the total crack area,the characteristic propagation velocities of desiccation cracks,and the acceleration of crack propagation.Through data fitting,theoretical formulas for soil water evaporation,propagation velocities of desiccation cracks,and crack propagation acceleration are derived,laying a foundation for future soil cracking theories.
基金supported by a subaward from Rutgers University,Center for Advanced Infrastructure&Transportation,under Grant no.69A3551847102 from the U.S.Department of Transportation,Office of the Assistant Secretary for Research and Technology(OST-R).
文摘The effects of desiccation cracking in clay soils on geotechnical constructions are substantial.This study investigates the viability of utilizing Enzyme-induced calcite precipitation(EICP),a bio inspired approach,as a potential solution for addressing desiccation cracking in fine-grain soils.For the EICP technique,crude soybean extract is employed for the purpose of urea hydrolysis.Multiple fluid samples,including a control sample,a cementation solution containing 1 M urea,0.675 M CaCl_(2),and 4 g/L milk,along with various concentrations of enzyme solutions(3-80 g/L),were tested for the study.To evaluate the surface cracking patterns,the method involved constant monitoring and photo recording using a high-resolution camera aided by image processing software.The results showed that fine-grain soils improved from increased calcite precipitation and decreased desiccation cracking intensity when the EICP method was used.Cementation and enzyme solution with low concentrations(3 g/L and 10 g/L)had similar effects on crack remediation,suggesting a modest influence.In contrast to the sample treated with water,the crack network remained unaltered in this case.CaCO3 precipitation within the void area kept the crack network in place even as the void thickness decreased at increasing enzyme concentrations(30 g/L,50 g/L,and 80 g/L).Wetting and drying cycles were found to decrease the crack ratio,crack width,and crack length in the EICP-treated sample,particularly under higher concentrations of urease enzyme.Lower enzyme concentrations of 3 g/L and 10 g/L have minimal impact on crack remediation but effectively inhibit new crack formation.Furthermore,higher enzyme concentrations result in calcium carbonate precipitates,forming a soil crust and increasing surface roughness.The study aims to enhance understanding of the EICP methodology and to provide novel perspectives on potential uses for soil enhancement.
基金support from the National Natural Science Foundation of China(Grant No.42172290,42230710,41925012)the Natural Science Foundation of Jiangsu Province(Grant No.BK20221250).
文摘The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporation,while a digital camera was utilized to capture the initiation and progression of soil surface cracking.Results indicate that in the early drying process,the rate of evapotranspiration in vegetated soil correlates positively with leaf biomass.For soil samples with the same layer thickness,the constant rate stage duration is consistently shorter in vegetated soil samples than in their bare soil counterparts.As the layer thickness increases,both vegetated and bare soil samples crack at higher water content.However,vegetated soil samples crack at lower water content than their bare soil counterparts.Vegetation significantly reduces the soil surface crack ratio and improves the soil crack resistance.The crack reduction ratio is positively correlated with both root weight and length density.In thicker vegetated soil layers,the final surface crack length noticeably declines.
基金supported by the National Natural Science Foundation of China(Grant Nos.41925012,42230710,42172290)the Natural Science Foundation of Jiangsu Province(Grant No.BK20211087)+2 种基金the Key Laboratory Cooperation Special Project of Western Cross Team of Western Light,CAS(Grant No.xbzg-zdsys-202107)the China Scholarship Council(Grant No.202206190069)the Fundamental Research Funds for the Central Universities。
文摘Drought-induced desiccation cracking can trigger several weakening mechanisms in surface soils,potentially precipitating instability and failure of slopes and earthen structures.To investigate the potential application of distributed fibre optical sensing(DFOS)based on optical frequency domain reflectometry(OFDR)technology in characterizing the twodimensional(2D)desiccation cracking processes of surface soils,a comprehensive test device is utilized to conduct soil evaporation tests,continuously record water content changes,desiccation cracking evolution,and FO sensing strain status.A deep learning-based quantitative analysis method is employed to meticulously examine the relationship between 2D cracking geometric parameters and strain status.The comprehensive analysis not only reveals the mutual feedback response mechanism between the strain status and the soil evaporation-shrinkage-cracking processes,but also clarifies the early detection distance of OFDR technology for 2D desiccation cracking.Specifically,OFDR technology can detect the propagation of horizontal desiccation cracks up to 23 mm in advance with a strain measurement accuracy of 1με.To address the spatial continuity issue in OFDR sensing strain data,an innovative high-resolution characterization framework is proposed by combining the finite element method(FEM)and OFDR technology,referred to as the FEM-OFDR framework.Comparative results indicate that the proposed FEM significantly surpasses both the kriging and radial basis function(RBF)methods in inferring missing OFDR sensing strain data.Notably,during the drying process,reaching a critical water content causes the local decoupling between the uncracked clods and the substrate,resulting in a decreasing trend in the sensing strain at the crack position.This study provides crucial technical means and theoretical support for a deeper understanding of the mechanisms driving 2D desiccation-induced shrinkage and cracking in surface soils.
基金supported by the National Natural Science Foundation of China(Grant Nos.41925012,42230710)Key Laboratory Cooperation Special Project of Western Cross Team of Western Light,Chinese Academy of Sciences(Grant No.xbzg-zdsys-202107).
文摘Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking.This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils.To validate the feasibility and efficacy of the proposed approach,direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents.Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance.During this period,the effects of W-OH treatment concentration and water content on tensile properties,soil suction and microstructure were investigated.The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil,which not only effectively enhances the tensile strength and failure displacement,but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior.The suction measurements and mercury intrusion porosimetry(MIP)tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores.Combined with the microstructural analysis,it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles.Moreover,desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking.With the increase of W-OH treatment concentration,the surface crack ratio and total crack length are significantly reduced.This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance.
基金supported by the National Natural Science Foundation of China(Grant No.51008120)the Youth Chenguang Project of Science and Technology of Wuhan City(Grant No.201271031418)the Outstanding Young Talent Program of Hubei Province(Grant No.2010 CDA091)
文摘Both cracks in clay liner and the complex composition of landfill leachate might have effects on the hydraulic conductivity of a compacted clay liner. In this study, the hydraulic conductivities of natural clay and bentonite-modified clay with and without desiccation cracks were measured, respectively, using three types of liquids as permeating liquid： 2 500 mg/L acetic acid solution, 0.5 mol/L CaCl2 solution, and tap water. When tap water was adopted as the permeating liquid, desiccation cracks resulted in increases in the average value of hydraulic conductivity： a 25-fold increase for the natural clay and a 5.7-fold increase for the bentonite-modified clay. It was also found out that the strong selfhealing capability of bentonite helped to reduce the adverse impact of cracks on hydraulic performance. In contrast to tap water, simulated leachates（acetic acid and CaCl2 solutions） show no adverse effect on the hydraulic conductivities of natural and bentonite-modified clays. It is concluded that desiccation cracks and bentonite have more significant effects on hydraulic performance than simulated leachates.
基金supported by National Natural Science Foundation of China(Grant No.42050201)National Key Research and Development Program of China(Grant No.2020YFC1522200)。
文摘Dry-wet cycle is a key factor in surface weathering of earthen heritage,which remains insufficiently explained.It involves the interaction of humidity,stress,and damage.Using the RFPA(realistic failure process analysis)numerical method,this study reproduced the processes of humidity diffusion,deformation,stress,and damage evolution under dry-wet cycles in the soil site of Suoyang City,China.The numerical results indicate that the drying phase following rainfall has the most significant deteriorative impact on the earthen heritage.The evaporation of surface moisture during this phase causes volume shrinkage,which in turn generates tensile stress and leads to the formation of numerous desiccation cracks.Desiccation cracks provide channels for moisture diffusion,which further exacerbates generation of the cracks,leading to a mutual promotion between the two phenomena.Furthermore,during the wetting phase,the model elements undergo hygroscopic expansion,resulting in a slight increase in strain and displacement.Previously formed cracks may exhibit temporary narrowing or closure,but will revert during the subsequent drying phase.Ultimately,the overall displacement increases with the number of dry-wet cycles.The findings provide a theoretical foundation for protection against surface weathering and other damage in earthen heritage in arid regions.
基金Under the auspices of National Natural Science Foundation of China(No.41201335)
文摘The Songnen Plain has a typical soda-saline soil, which often shrinks and cracks under natural conditions during water evaporation. This study aims to analyze the relationships between the crack characteristics and the soil properties of soda-saline soils quantitatively, and attempts to establish prediction models for the main soil properties of soda-saline soils based on the results. In order to achieve these objectives, a desiccation cracking test was conducted using 17 soil specimens with different salinity levels under controlled laboratory conditions. Correlation analysis was then performed between the crack characteristics and the soil properties. The results indicate that the crack characteristics can well represent the surface appearances of cracked soils, they also can well distinguish the salinity levels of soda-saline soils while the clay contents and mineralogical compositions of soils are stable. Among the crack characteristics, crack length has the best relationships with the salinity levels of soda-saline soils. Specifically, the crack length has high correlation(R2 > 0.87) with the electrical conductivity(EC), Na+, CO32– and the salinity, it also has reasonable relationship(R2 > 0.68) with HCO3–, this indicates crack length can be well used for the prediction of these properties of soda-saline soils.
基金part of a project investigating the nature and extent of paleo-permafrost in West China led by Professor Huijun Jin with the State Key Laboratory of Frozen Soils Engineering (SKLFSE), Northwest Institute of Eco-Environment and Resources (NIEER), Chinese Academy of Sciences (CAS), Lanzhou, under the auspices of National Natural Science Foundation of China (NSFC) (Grant No.41811530093)Russian Federation Bureau of Research (RFBR Grant No.18-5553054) on Formation, modern state of Pleistocene cryogenic deposits in Eastern Asia, and forecast of their dynamics in relation to the ongoing climatic variations+1 种基金Key Programs of the International Cooperation Department of the Chinese Academy of Sciences (CAS) on "Changing permafrost in China, Russia and Mongolia and its impacts on key engineered infrastructures"CAS Strategic Pilot Science and Technology Project (Grant No.XDA05120302) "Permafrost in China during the Holocene Megathermal Period and Last Glaciation Maximum"。
文摘Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of either permafrost or seasonal frost during the Late Pleistocene and early Holocene. Wedges of about 1 m in depth form polygonal nets of 2-3 m in diameter(type B). They contrast with wedges of 3-4 m in depth that form polygons of 10-15 m in diameter(type A).This review focuses upon the highly variable size of the inferred polygon nets and discusses the problem of differentiating between seasonally and perennially frozen ground, or between seasonal frost and permafrost.
基金support by the French Space Agency CNES,PNP(Programme National de Planétologie)TOSCA(Terre,Océan,Surfaces Continentales,Atmosphère)
文摘In continental and oceanic conditions, clay-rich deposits are characterised by the development of polygonal fracture systems（PFS）. PFS can increase the vertical permeability of clay-rich deposits（mean permeability ≤10-16 m2） and are pathways for fluids. On continents, the width of PFS ranges from centimeters to hundreds of meters, while in oceanic contexts they are up to a few kilometers large. These structures are linked to water-solid separation during deposition, consolidation and complete fluid squeeze of the clay horizon. During the last few decades, modeling of melt migration in partially molten plastic rocks led to rigorous quantifications of two-phase flows with a particular emphasis on 2D and 3D induced flow structures. The numerical modeling shows that the melt migrates on distances almost equal to a few times the compaction length L that depends on permeability and viscosity. Consequently, polygonal structures in partially molten plastic rocks are resulted from the melt-rock separation and their sizes are proportional to L. Applying these results to fluid-solid separation in clay-rich horizons, we show that（1） centimetric to kilometric PFS are resulted from the dramatic increase of L during compaction and（2）, this process involves agglomerates with 100 μm to 1 mm size.
文摘The phenomena of shrinkage and swelling of clay induce damage to housing structures every year. Precipitation, climatic changes and drought are the cause of wall cracks due to subsidence or swelling of the supporting soil. This movement alters the balance between the soil and the structures. To explain this defection, the soil is made up of three elements: the solid, the liquid and the gas. Sometimes in a natural way or following a human intervention, one of these elements undergoes an abnormal variation that causes the loss of the balance between land and works. It is in this sense that this article deals on the one hand with the factors of predisposition and triggering of the phenomena of shrinkage-swelling of the clay soils of Diamniadio and on the other hand, the factors of aggravation linked to the lithological heterogeneity and the variation in the thickness of the layers susceptible to shrinkage-swelling. The studies carried out have enabled a deeper understanding of the behavior of expansive soils following their interactions with climate, vegetation, hydrology, hydrogeology, constructions among others, but also the influence of lateral and vertical variations of fine soil facies.
文摘Crack patterns observed in nature have attracted the interest of researchers in various fields, and the mechanism of the pattern formation has been investigated. However, the phenomenon is very complicated, and many factors affect the process. Therefore, we are motivated to construct a general simulation code with a simple algorithm. In this study, crack pattern formation due to shrinkage caused by the drying of a wet material was simulated. The process was simplified as follows: tensile force is generated in the model, and a crack is generated when the tension exceeds a critical value. The tensile forces in the x and y directions are independently evaluated. A crack propagates perpendicular to the tension until it reaches another crack or a boundary. Based on this modeling, simulations with a two-dimensional square domain were performed. Consequently, a cross-divided pattern was generated. Assuming zigzag crack propagation, more realistic patterns were obtained. The effects of the boundary and domain size were also considered, and various characteristic patterns were obtained. Furthermore, the orientation dependency was simulated, and 45˚ declined patterns and rectangularly divided patterns were generated. The model presented in this study is very simplified and is expected to be applicable to various objects.
文摘Biochar is a carbon-rich material obtained after thermochemical conversion of biomass under no oxygen environment.The effect of biochar amendment on soil properties,such as water retention,infiltration and desiccation crack potential was studied in the recent years.However,the effect of biochar or feedstock type on these properties is not explicit.This study investigates the effect of two different(in terms of feedstock)types of biochar on the water retention,infiltration and desiccation crack-ing behavior of compacted silty sand.Water retention characteristics,infiltration rate and the progression of desiccation cracks were measured after compacting soil amended with 5-10%(w/w)biochar produced from water hyacinth(WHB)and mesquite.Measurements were also taken for an unpyrolyzed material coir pith(CP,sourced from coconut husk)-amended soil for comparing the results of biochar-amended soil.The results show that the amendment of 5%to 10%biochar increased the maximum water holding capacity(θs),air entry value(AEV)and water content at 1500 kPa(θ1500)of the soil,whereas decreased the infiltration rate and peak crack intensity factor(CIF)of the soil.Moreover,the application of CP increased the infiltration rate.The amendment of WHB showed the highest increment in AEV andθ1500 and the highest decrement in infiltration rate and CIF compared to the other amendments.Based on the results,it is advisable to use the WHB-amended soil in bioengineered structures that could promote the growth of vegetation by higher water retention and could reduce the potential of leachate formation by decreasing water infiltration and desiccation crack potential.
