Soil Shrinkage Research Articles

Computational Modeling of Desiccation Properties (CW, LS, and VS) of Waste-Based Activated Ash-Treated Black Cotton Soil for Sustainable Subgrade Using Artificial Neural Network, Gray-Wolf, and Moth-Flame Optimization Techniques

Artificial neural network (ANN), gray-wolf, and moth-flame optimization (GWO and MFO) techniques have been used in this research work to predict the effect of activated sawdust ash (ASDA) on the crack width (CW), linear shrinkage (LS), and volumetric shrinkage (VS) of a black cotton soil utilized as a subgrade material. Problematic soils or black cotton soils are not good pavement foundation materials except that they are pretreated in order to meet the basic strength characteristics required for roads in Nigeria. Due to this reason, there has been ongoing research to evaluate the best practices in which black cotton soils can be favorably utilized in earthwork construction. On the other hand, there is a huge concern on the solid waste management system in the wood processing environment and the recycling of sawdust into ash and its reuse as an alternative binder has offered a sustainable disposal system. The work tries to use AI-based techniques to predict the crack and shrinkage behaviors of BCS treated with saw dust ash activated with alkali materials. There was appreciable improvement in the shrinkage and crack parameters over the 30-day drying period due to the addition of ASDA. The intelligent model results showed that the three techniques successfully predicted the CW, LS, and VS with a performance accuracy above 90%, while ANN produced the minimal error in performance outperforming the other techniques. Sensitivity study showed that the drying time (T) was the most influential of the studied parameter. Hence, soil stabilization has shown its potential system of waste management in the wood processing industry.

Experimental Investigation on the Impact of Drying–Wetting Cycles on the Shrink–Swell Behavior of Clay Loam in Farmland

Soil shrink–swell behavior is a common phenomenon in farmland, which usually alters the process of water and solute migration in soil. In this paper, we report on a phenomenological investigation aimed at exploring the impact of drying–wetting cycles on the shrink–swell behavior of soil in farmland. Samples were prepared using clay loam collected from farmland and subjected to four drying–wetting cycles. The vertical deformation of soil was measured by a vernier caliper, and the horizontal deformation was captured by a digital camera and then calculated via an image processing technique. The results showed that the height, equivalent diameter, volume and shrinkage-swelling potential of the soil decreased with the repeated cycles. Irreversible deformation (shrinkage accumulation) was observed during cycles, suggesting that soil cracks might form owing to previous drying rather than current drying. The vertical shrinkage process consisted of two stages: a declining stage and a residual stage, while the horizontal shrinkage process had one more stage, a constant stage at the initial time of drying. The VG-Peng model fit the soil shrinkage curves very well, and all shrinkage curves had four complete shrinkage zones. Drying–wetting cycles had a substantial impact on the soil shrinkage curves, causing significant changes in the distribution of void ratio and moisture ratio in the four zones. However, the impact weakened as the number of cycles increased because the soil structure became more stable. Vertical shrinkage dominated soil deformation at the early stage of drying owing to the effect of gravity, while nearly isotropic shrinkage occurred after entering residual shrinkage. Our study revealed the irreversible deformation and deformation anisotropy of clay loam collected from farmland during drying–wetting cycles and analyzed the shrink–swell behavior during cycles from both macroscopic and microscopic points of view. The results are expected to improve the understanding of the shrink–swell behavior of clay loam and the development of soil desiccation cracks, which will be benefit research on water and solute migration in farmland.

Sap flow monitoring of two Australian native tree species in a suburban setting: Implications for tree selection and management

Sap flow, the transport of fluid in the water-conducting xylem tissues of plants, is commonly measured in studies of plant-water relationships by the heat pulse velocity method. Publications have been rare of long-term sap flow measurements for individual trees in a suburban environment. Plant-water relations in urban settings are essential for promoting urban greening where there is a perceived danger to infrastructure and buildings from planting trees in streets on clay sites. The function of residential houses built on reactive clays can be significantly impaired and walls of buildings cracked if considerable amounts of water are extracted from the soil by the root system of a tree or a group of trees in close proximity, leading to localised soil shrinkage settlement. This part of the wider study aimed to monitor sap flow of eight individual Australian native trees from two species using the heat ratio method (HRM) in the field over 12 months. The analysis of monthly sap flow volume showed a similar pattern for all monitored trees, although daily water demand varied substantially. Methods for estimating tree leaf surface area, crown shape and crown volume were investigated and the equation for calculating thermal diffusivity (k) and sap flow velocity on the basis of the HRM was reviewed. It has been proposed that k may vary substantially depending on how thermal conductivity (K) is estimated, which could lead to significant discrepancies for estimations of plant transpiration. Two K models (KHog and KVan) were investigated and it was found that the impact on mean daily sap volume was negligible for the trees in this study.

Study of Shrinkage and Swelling Phenomena in Clay Soils of Fanaye (Middle Senegal River Valley): Simulation of Water Transfers in a Soil Column

Soil degradation due to shrinkage and swelling of these clay soils is a problem for agriculture. To understand the physical properties of the soils in this agricultural area, we will use an undisturbed soil monolith 60 cm high and 23 cm in diameter in the laboratory. This study quantified the swelling and shrinkage of these soils during a 10-month experiment. The determination of the hydrodynamic parameters of this monolith made it possible to simulate water transfers in a soil of constant volume and a water transfer in a soil of variable volume. The results of this simulation show significant differences between these two cases, hence the need to integrate the variations in soil volume into the simulation processes of water transfers.

Unified Elastic Modulus Characteristic Curve Equation for Variably Saturated Soils

A soil’s elastic modulus is a fundamental property defining the soil’s reversible stress-strain relation under mechanical and environmental loadings. It has been observed that a soil’s elastic modulus can increase up to several orders of magnitude from fully saturated to dry conditions due to two distinct soil water retention mechanisms: adsorption and capillarity. Adsorption affects interparticle stress through van der Waals and electrostatic attraction and interparticle friction coefficient through water film retained by soil sorptive potential. Capillarity governs interparticle stress through capillary pressure and surface tension. The onset and scaling laws of the two mechanisms depend on the soil properties of specific surface area, pore-size distribution, cation exchange capacity, and soil mineralogy. These mechanisms are unified by a proposed elastic modulus characteristic curve (EMCC) equation. It is demonstrated that the proposed EMCC equation can well describe the moisture-dependent elastic modulus of a wide array of soils. Further, an interrelation among the EMCC equation, suction stress and soil shrinkage curves is established, which can greatly facilitate predicting suction stress from soil shrinkage curves and vice versa, further validating the EMCC equation in capturing soil’s hydromechanical behavior. The practical importance of the EMCC equation is demonstrated through prediction of ground heave of various soils due to a hypothetical flooding event.

The application of vapour equilibrium technique to control suction to study the shrinkage and water retention of compacted Claystone-Bentonite mixtures

Understanding soil shrinkage and retaining water is essential for learning more about the possibility of cracking of liner. Moreover, the factors that influence it are also important to know to improve the material tested as hazardous waste liners. The vapour equilibrium technique is widely used to control suction of compacted soils experiencing drying-wetting phenomena. It is considered to be inexpensive, simple, and has the ability to adequately control the suction applied to soil samples. This paper, therefore, describes its application in studying the shrinkage and water retention in compacted claystone-bentonite mixtures. This involved using five saturated salt solutions including potassium sulphate (K2SO4), potassium chloride (KCl), sodium chloride (NaCl), potassium carbonate (K2CO3), and magnesium chloride (MgCl2.6H2O). The sample was allowed to be in equilibrium with the relative humidity salt solution and a calliper was used to measure the dimensions every day up to when this was achieved. The results showed the bentonite in the mixture affects the amount of shrinkage and water retention while the sample’s initial moisture content was also found to be very influential on the magnitude of the primary and residual shrinkage. Moreover, the sample’s ability to hold water was almost the same without differentiating the initial water content at a total suction of more than 41084.91 kPa.

Predictive Model for Soil Shrinkage Characteristic Curve of High Plastic Soils

Abstract Soil shrinkage characteristic curve (SSCC) is the relationship between gravimetric water content (w) and void ratio for a soil drying under zero external stress. It is mandatory for determining the soil-water characteristic curve and modeling water transport in high plastic soils, which exhibit significant volume change. The knowledge of SSCC is required for calculating the degree of saturation or volumetric water content from the known w. However, the measurement of SSCC is extremely tedious and time consuming, particularly for highly plastic clays like bentonite. Therefore, this study attempts to develop a predictive model for SSCC of highly plastic soils based on easily measurable index property, plasticity index (PI). Four bentonites and nine bentonite–fly ash mixes were used to encompass soils with a wide range of PI. The results were used to study the influence of plasticity characteristics on SSCC. The key parameters of SSCC; minimum void ratio, water content at air entry (wAE) and the shrinkage limit (wS) was effectively correlated with PI. The measured SSCCs were quantified using the Fredlund, Wilson, and Fredlund (2002) model, and equations were proposed to estimate the model parameters using PI. The efficacy of the proposed model was demonstrated using an independent data set of bentonite and its mixes with fly ash as well as data from the literature. It was found that the proposed model can predict the SSCC of highly plastic soils with reasonable accuracy.

The Effect of Circulating Fluidised Bed Bottom Ash Content on the Mechanical Properties and Drying Shrinkage of Cement-Stabilised Soil.

This study aimed to determine the effect of circulating fluidised bed bottom ash (CFB-BA) content on the mechanical properties and drying shrinkage of cement-stabilised soil. Experiments were performed to study the changes in unconfined compressive strength and expansibility of cement-stabilised soil with different CFB-BA contents and the underlying mechanisms based on microscopic properties. The results show that CFB-BA can effectively increase the unconfined compressive strength of the specimen and reduce the amount of cement in the soil. When the combined content of CFB-BA and cement in the soil was 30%, the unconfined compressive strength of the specimen with C/CFB = 2 after 60 days of curing was 10.138 MPa, which is 1.4 times that of the pure cement specimen. However, the CFB-BA does not significantly improve the strength of the soil and cannot be added alone as a cementing material to the soil. Additionally, swelling tests showed that the addition of CFB-BA to cement-stabilised soil can significantly reduce the drying shrinkage. This research project provides reference values for the application of CFB-BA in cement–soil mixing piles, including compressive strength and the reduction in the shrinkage deformation of specimens.

Study on Strength, Water Stability, Shrinkage, and Microstructure of CFB Slag Modified Cement Stabilized Clay.

Circulating fluidized bed slag (CFBS) is an industrial waste produced by coal combustion in power plants. To explore the application of CFB slag in cement-stabilized bases, this paper studies the influence of different dosage of CFBS on the mechanics, water stability, and shrinkage of cement-stabilized soil using laboratory experiments. The hydration activity and interface morphology of CFBS in cement-stabilized clay were observed using XRD and SEM. The improvement mechanism of CFBS on the performance of cement-stabilized clay was revealed. The results indicated that, compared with cement-stabilized clay, cement–CFBS-stabilized clay exhibited better mechanical and water stability, and significantly inhibited the shrinkage deformation of cement-stabilized clay. When the addition of CFBS was 70%, cement–CFBS-stabilized clay had the best mechanics and durability. Microscopic tests show that CFBS contains more active silicon aluminum oxide, which is easily dissolved and the hydration of which produces more gel products, so the mixture structure is denser, the strength is improved, and water does not easily evaporate; it has the characteristics of micro expansion which compensates for dry shrinkage deformation.

Experimental and Numerical Analysis of Soil Cracking Characteristics under Evaporation

There are numerous cracks on soil surface in nature. These cracks are mainly formed by the continuous water loss and shrinkage of soil under evaporation. Cracks have an important effect on the properties of soil. The analysis of soil moisture movement and cracking characteristics under evaporation is of great significance to the engineering construction in the cracked soil area. In this work, an experimental study was conducted to investigate the development of soil cracks. Crack geometrical parameters were acquired at various developmental stages. According to this, the crack evolution characteristic was described qualitatively. The law of soil water movement was analyzed through the numerical simulation of evaporation effect on cracked soil. The relationship between soil moisture content and crack width was revealed, and the dynamic prediction of crack development under evaporation was realized. The results show that the development and evaporation process of soil cracks can be divided into three distinct stages, and the longer the stable evaporation time, the greater the development of cracks.

THM analysis of a soil drying test in an environmental chamber: The role of boundary conditions

This paper presents the numerical analysis of an experimental soil drying test carried on an initially slurry soil specimen with controlled temperature and relative humidity in a laboratory environmental chamber. The imposed drying conditions lead to evaporation and a consequent soil shrinkage, triggering a perimeter crack between soil body and mould. The numerical analysis follows a THM approach with two objectives: to identify the soil parameters that govern drying, and to determine the influence of the perimeter crack on evaporation. Identifying the boundary condition requires defining the vapour and heat fluxes, the corresponding transfer coefficients, and the influence of the perimeter crack. The simulations are provided in 3 separate blocks with gradually added complexity until a good fit with the experimental data is obtained. The approach signifies the importance of accounting for the mechanical problem, the initial self-weight settlements of the slurry, the wind effect in the chamber and the evaporation from the exposed crack surface. The local atmosphere within the formed crack, however, differs from the surface, requiring the use of different vapour transfer coefficients at the distinct surfaces. The simulations were assessed based on the ability to reproduce the water loss, developing suction profile and soil relative humidity.

Long‐term effect of sugarcane residue management and chemical fertilization on soil physical properties in South Africa

AbstractSugarcane (Saccharum officinarum L.), an intensive, long‐term, monoculture, economical crop in South Africa, is known to degrade soil characteristics. Soil structure, a key indicator of soil health and biomass production potential, is manageable by agricultural practices. This study aims to evaluate the effect of crop residue management practices (mulching, burning with residues scattered or removed) and mineral fertilization (with or without) on soil structure by analyzing soil shrinkage curves (SSCs) and other soil physical and chemical properties in a long‐term sugarcane trial established in 1939. The SSC provides descriptive structural soil data by differentiating and characterizing two pore systems (plasma and structural pores). By analyzing the SSC of 24 plots (four replicates each treatment), residue management and fertilization practices were found to have statistically and physically significant effects on hydrostructural variables. Partial redundancy analysis showed that residue management practices had a slightly higher effect (19% of total variance) on hydrostructural variables compared with fertilization (12%). The main hydrostructural variables representing the management effect were total soil shrinkage, specific volume, and swelling capacity of the plasma, which were higher in mulched and/or unfertilized plots, indicating that soil was less compact, and shrinkage was more intense, including at the plasma level. The stronger structural dynamics and aggregate stability of the soil were explained by the behavior of the primary aggregates (peds), which were more porous and reactive during the drying process. This study highlights the importance of mulching and limited fertilization to maintain soil structure in the long term while still ensuring yield production.

Utilization of biomass-based by-product lignin to suppress moisture loss-induced shrinkage of silty soil

The global stockpiles of by-product lignin are increasing rapidly with the growing demand on wood-based industry and biomass energy, creating a potential threat to environmental safety without proper disposal. The presented study aimed to evaluate the feasibility of utilizing biomass-based by-product lignin to suppress the shrinkage of silt expected as filling material in engineering construction. A series of laboratory experiments were conducted to investigate the variations in geometry size, mass loss Δm, moisture content w, and unconfined compressive strength qu of the treated samples exposed to the artificial dry condition. The effects of additive dosage and curing time on shrinkage behaviors of lignin treated silt were analyzed. The roles of matric suction on qu and soil microstructure were discussed to understand the mechanism leading to the soil shrinkage. The test results demonstrated that the addition of lignin effectively suppressed shrinkage of compacted silt subjected to dry curing. Both linear shrinkage rate es and volumetric shrinkage rate ev increased with an increase in lignin dosage, indicating excessive addition of lignin produced a negative impact on the shrinkage resistance. The values of es and ev of lignin treated samples were controlled within 1.0% and 3.0%, respectively. As compared to quicklime, lignin exhibited slightly inferior performance of suppressing shrinkage, while it promoted the water-holding capacity of the treated silt. The matric suction resulted from moisture loss was beneficial for strength improvement and also accelerated the process of soil shrinkage. The shrinkage characteristics of lignin treated silt mainly depended on the combined functions of lignin cementation and matric suction. Additional research is recommended to quantitatively evaluate the matric suction variation of lignin treated soils in dry environment. The outcomes of this study are invaluable in facilitating sustainable soil treatment in engineering construction and providing a viable answer to the cleaner production of biomass-based business.

Soil Shrinkage Characterization of Low Plasticity Soil Using Digital Image Analysis Process

The goal of this paper is to better understand the shrinkage behavior of low plasticity (CL) soil, which is common in Warangal, India. Understanding the tensile strength and hydro-mechanical response of soil requires an understanding of the contraction behavior of soil caused by drying during wet-dry moisture cycles. With the use of simple and reliable experimental approaches, the shrinkage mechanism and behavior with suction variation are characterized and described in this study. The findings are related to the change in suction, water content, and void ratio of soil that has been air-dried from complete saturation to dryness. The proposed framework uses two simple approaches to understand soil water retention during the drying phase: one to quantify the suction potential and the other to characterize the shrinkage mechanism. In addition, the use of digital image processing (DIP) to capture sample shrinkage using a simple experimental setup is thoroughly discussed. ImageJ software has been found to be feasible for DIP and to quantify the volume change of laboratory samples. The absence of well-structured soil phases or macropores is attributable to the presence of only normal shrinkage and zero shrinkage phases in the tested soil. In terms of water–retention behavior, the shrinkage curve, and the suction curve are very similar. The effects of capillary suction on the shrinkage response of low plastic soil have been observed, emphasizing the importance of characterizing soil shrinkage behavior using suction as a stress-state variable in volume change studies.

Understanding the performance of expansive subgrade materials treated with non-traditional stabilisers: A review

Expansive soils are problematic soils which pose a risk to the safety of civil engineering structures. These soils can be treated by compaction or by adding additives to the soil. Where the strength and properties of expansive soil cannot be improved via mechanical stabilisation (Compaction), a desirable strength can be achieved through the use of chemical admixture techniques. The swelling and shrinkage of expansive soils cause movement in the soil mass resulting in a deferential settlement in engineering structures such as roads and building leading to cracks and subsequent failure leading to high cost of maintenance. Calcium based additives such as cement and lime have been used in expansive subgrade stabilisation to enhance the strength, reduce swell and subsequent differential settlement. However, the growing concerns on carbon dioxide (CO2) emission and climate change have reignited the need for a more sustainable soil stabilisation techniques using waste materials. In this study, non-traditional expansive subgrade treatment techniques using sustainable waste materials with respect to their efficiency in improving the geotechnical engineering properties of the subgrade materials have been investigated and reviewed. This study also discusses the engineering problems associated with expansive soils, proposing an effective, efficient, cheaper and sustainable application of non-traditional stabilisers in expansive soil stabilisation. The study concludes that, the addition of non-traditional stabilisers in expansive subgrade stabilisation using chemical stabilisation techniques can improve the engineering properties of expansive subgrade materials.

Some Geotechnical Properties of Plastic Soil Enhanced with Cement Dust

Plastic soil exhibits unfavorited geotechnical properties (when saturation), which causes negative defects to engineering structures. Different attempts (included various materials) were conducted to proffer solutions to such defects by experimenting in practical ways. On one hand, these attempts aimed to improve the engineering characteristics of plastic soil, and on the other hand, to use problematic waste materials as a stabilizer, like cement kiln dust, and to reduce environmental hazards. This paper explored the shrinkage, plasticity, and strength behavior of plastic soil enhanced with cement dust. The cement dust contents were 0%, 5%, 10%, 15% and 20% by dry weight of soil. An experimental series of shrinkage and plasticity tests and unconfined compression tests were carried out to explore the effects of cement dust on the quantitative amount of shrinkage, plasticity characteristics, and shear strength experienced by plastic soil. The effects of curing on soil strength were also investigated. The finding of this paper showed that the critical behavior and plasticity of plastic soil could be reduced by mixing the soil with 15% or 20% of cement dust. The undrained shear strength, cu, of plastic soil-cement dust mixtures increased with the increasing dust content up to 20%. In fact, this strength was affected by the curing period. The best enhancement was attained when the content of cement dust was 20%, and the undrained shear strength was increased more than three times at this content.

Utilization of Blast-Furnace Slag as a Standalone Stabilizer for High Sulfate-Bearing Soils

This paper presents experimental results and analysis of sulfate-bearing soils treated with ground granulated blast-furnace slag (GGBS). The experiments involve the unconfined compression strength test, shrinkage, free swelling, suction measurements, and microstructural examination. Short- and long-term swelling tests were conducted to inspect the durability of GGBS stabilization against the sulfate-induced heave. The concept of the shrinkage curve was employed to elucidate how GGBS stabilization alleviates soil shrinkage behavior and alters the pore size distribution. The results manifested that 7% GGBS was sufficiently adequate to improve the 28-day strength of the tested sulfate-bearing soils about five times. The GGBS treatment mainly results in the decline of calcium sulfate content and the formation of calcium silicate hydrate, ettringite, and calcite. The results of long-term swelling tests indicated a delayed sulfate-induced heave that started beyond a month from the time of exposing the treated soils to water. The delayed heave was still not significant as compared with that of the untreated control soil specimens. Accordingly, it is recommended that the treated sulfate-bearing soils are tested with the selected GGBS content for any delayed swelling before application in the field. The GGBS treatment has significantly escalated suction magnitude during curing mainly due to the consumption of water in the hydration process and the formation of ettringite.

A FDEM 3D moisture migration-fracture model for simulation of soil shrinkage and desiccation cracking

This paper proposes a three-dimensional moisture migration model, which can simulate the moisture migration process in soil. A simple moisture transport example with analytic solutions is given to verify the correctness of the 3D moisture migration model. Combining the moisture migration model with the combined finite discrete element method (FDEM), a moisture migration-fracture model that simulates soil shrinkage and cracking is constructed and implemented in an in-house GPU parallel multiphysics finite element-discrete element software, namely MultiFracs. The calculation process of the three-dimensional moisture migration-fracture model is: first obtain the moisture field distribution of the solution domain through the moisture migration model; then obtain the shrinkage stress in all tetrahedral elements according to the change of the moisture field; finally, apply the shrinkage stress as a load to perform the deformation and fracture calculations of FDEM. The 3D moisture migration-fracture model is used to simulate an experiment of clayey soil shrinkage cracking. Image recognition technology is used to carry out quantitative statistics and analysis of desiccation crack patterns. The simulation results show high consistency with the laboratory experiment. Moreover, the influences of shrinkage parameter, water evaporation rate, and layer thickness on clayey soil desiccation cracking are studied comprehensively.

Effects of soil shrinkage in permanent gullies formation: The case of Benggang erosion in the granite area of southern China

Effects of soil shrinkage in permanent gullies formation: The case of Benggang erosion in the granite area of southern China

A Unified Approach for Establishing Soil Water Retention and Volume Change Behavior of Soft Soils

Abstract The assumption of treating the specimen volume as constant while experimentally determining the soil water retention curve (SWRC) of soils is valid only for nonplastic, granular soils. Fine-grained soils usually undergo significant volume change during dewatering and densification, and therefore such an assumption is misleading, even falsifying. The need for developing an easy-to-use lab-scale technique that can enable continuous monitoring of the evolutions in volume, suction, and moisture content of a progressively drying soft soil specimen is evident in the field of characterizing unsaturated soils. Such a method is relevant to establishing SWRC and soil shrinkage curve (SSC) of soft soils that exhibit an appreciable degree of deformation upon subjection to dewatering. To this end, a simple yet improvised method based on the balloon technique incorporating a commercially available high-capacity polymer tensiometer has been proposed to establish SWRC-SSC of soft soils. A comparison between the SWRC and SSC obtained through the proposed method and the conventional methods demonstrated a satisfactory degree of agreement. Densification of the materials realized under the influence of mechanical and hydraulic stresses has been discussed through a comparative analysis between the results from the proposed method and one-dimensional odometer test. For soft soils, the proposed method is particularly appropriate for establishing SWRC in terms of volumetric moisture content and degree of saturation through just a single test.