Expansive Clay Research Articles

Enhancement of Resilient Modulus and Strength of Expansive Clay Stabilized by Wool and Agricultural Waste

Enhancement of Resilient Modulus and Strength of Expansive Clay Stabilized by Wool and Agricultural Waste

Strength and dilatancy of an unsaturated expansive soil at high suction levels

A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength. The suction of the soil samples was controlled using a vapour equilibrium technique, with four suction levels ranging from 3.29 MPa to 198.14 MPa, where water retention is dominated by adsorption. The experimental results show that the tested soil exhibits a brittle failure mode under high suction, significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction. This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength, causes the soil to fail before reaching the critical state, a phenomenon not observed in soils under high suction, and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement. The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength, with the maximum dilatancy angle increasing with suction and decreasing with confining pressure. However, the initial dry density has a negligible impact on the soil's dilatancy under high suction levels. This observation further supports that, for unsaturated soils under high suction levels, dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles.

Enhancing Soil Quality: A Systematic Analysis of Solutions for Expansive Clays in Scopus Indexed Literature

Enhancing Soil Quality: A Systematic Analysis of Solutions for Expansive Clays in Scopus Indexed Literature

Mechanistic analysis of urban tree-soil interactions: Species-specific water use and desiccation effects on expansive clays

Mechanistic analysis of urban tree-soil interactions: Species-specific water use and desiccation effects on expansive clays

Study on the disintegration characteristics of expansive stiff clay: with consideration of expansion-disintegration interaction

Study on the disintegration characteristics of expansive stiff clay: with consideration of expansion-disintegration interaction

Sustainable soil stabilization using industrial waste ash: Enhancing expansive clay properties

This study investigates the use of various industrial waste materials—silica fume (SF), cement kiln dust (CKD), calcium carbide residue (CCR), rice husk ash (RHA), and ground granulated blast furnace slag (GGBS)—as eco-friendly stabilizers for expansive clay soil (ECS). Laboratory tests were conducted to assess the impact of different proportions (3 %, 6 %, and 9 %) of these additives on the soil's physical, mechanical, and microstructural properties. Results indicated that the inclusion of industrial waste significantly improved the soil's behavior, with notable reductions in liquid limit (up to 37.66 %), plasticity index (up to 74.76 %), and swell potential. Additionally, unconfined compressive strength (UCS) and shear strength increased substantially, with UCS values rising from 114.64 kPa to 1582.91 kPa at 30 days of curing for 9 % GGBS. Microstructural analyses confirmed the formation of cementitious compounds, which enhanced soil particle bonding and durability. These findings suggest that industrial waste materials can serve as effective and sustainable alternatives to traditional soil stabilizers, offering both performance improvements and environmental benefits.

Quantitative investigation of temperature-dependent bound water degeneration in bentonite clays

Temperature increases in saturated clay alter the physicochemical clay-water interactions and may lead to the conversion of bound water into free water. These changes significantly influence the physical, chemical, and engineering properties of clays, which are critical for geotechnical and geological engineering and minimizing risks in areas with expansive clay soils. However, quantifying this phenomenon remains challenging in the literature. This study presents a robust experimental approach for quantifying the thermal-induced conversion of bound water in clays, providing valuable insights into the mechanisms governing their thermo-mechanical behavior. A novel experimental method is proposed to quantify the degenerated bound water content in a clay system subjected to temperatures ranging from 20 to 50 °C. The research employs the siphon principle to examine volume changes in a clay system at elevated temperatures, focusing on measuring the conversion of bound water to free water. This method accounts for thermal expansion of both the soil constituents and the confining glass cylinder, as well as potential evaporation losses. To validate the setup's accuracy, a calibration test using standard Ottawa sand with negligible bound water was performed. After measuring system error, the primary outcome was calibrated. Results showed that at 30 °C, 40 °C, and 50 °C, 3 %, 9 %, and 15 % of the initial bound water, respectively, converted to free water.

Measuring shrinkage of expansive soils using a novel automated high‐frequency setup

AbstractSoil shrinkage characteristic curves are used to describe the shrinkage behavior and hydraulic properties of unsaturated soils. To construct soil shrinkage characteristic curves, a high‐data‐density measurement method is needed that relates water content to soil volume changes. We present a fully automated soil shrinkage measurement setup, based on the simplified evaporation method, to characterize the shrinkage behavior of undisturbed natural expansive clay soils. The high data density creates the opportunity to produce soil shrinkage characteristic curves without the need for a mathematical model. The technique allows for resaturation of the samples after drying, enabling differentiation between reversible and irreversible shrinkage. The setup consists of the commercialized HYPROP2 apparatus combined with optical distance sensors to measure the horizontal and vertical dimensions of the samples, yielding data on the sample volume, weight, and soil water suction. The measurement frequency is once per 10 min, and the measurement period is up to 4 weeks, providing a detailed time series of the drying and shrinkage characteristics. The setup can capture the different shrinkage phases and offers the opportunity to relate the soil shrinkage characteristic curve to soil water suction. The measurement data acquisition rate and accuracy enable detailed interpretation of soil water retention curves for nonrigid soils and are shown to be essential for understanding and quantifying the shrinkage potential of several types of deposits.

Effect of Calcium Carbide Residue on Shrinkage Mechanism of Clayey Subgrade Soil

ABSTRACT Calcium carbide residue (CCR) has been identified as an effective replacement for traditional lime for the stabilization of expansive soils. The shrinkage of expansive clay severely threatens the foundation layers’ long-term stability. The efficacy of CCR stabilization in reducing compressibility and enhancing the strength and stiffness of clay has been widely reported; however, the calcium-based additive stabilized soil tends to lose its engineered integrity under field-exposed seasonal moisture variation, specifically, shrinkage induced by prolonged drying. In this study, the shrinkage characteristic of CCR-treated clay (6%, 9%, and 12%) slurry was investigated by digital image analysis and mercury displacement method to quantify volumetric shrinkage strain. The results were compared with those of 4% and 6% lime-treated clay, which revealed the higher efficacy of CCR in reducing shrinkage strain by 47–57%. A characteristic shrinkage curve that depicted the significant variation of shrinkage phases in CCR-treated clay samples is developed. The dominance of the proportional shrinkage phase is observed in both untreated and treated clay samples. The shrinkage caused by evaporation, hydration, and decalcification is postulated in treated clays. This study is expected to contribute to the understanding of shrinkage mechanisms of CCR-treated clay and assist in the future design of stabilized embankment sections or subgrade for unpaved roads.

A Comparative Study of Real-World vs. Small-Scale Mat Foundations on Expansive Clay Soils for Low-Cost Housing

A Comparative Study of Real-World vs. Small-Scale Mat Foundations on Expansive Clay Soils for Low-Cost Housing

Expansive clay subgrade soil improvement using municipal solid waste fly ash: Experimental and numerical approach

The expansive soil under investigation has caused damage to lightweight structures due to its swelling and shrinkage characteristics in response to changing moisture content. The study aims to assess the impact of municipal solid waste (MSW) fly ash on the engineering properties of subgrade expansive soils and its influence on pavement structure deformation. The influence of municipal solid waste fly ash on expansive soils was evaluated using laboratory tests and finite element methods. The Abaqus software was used to investigate the effects of MSW fly ash on pavement structure deformation. The input parameters employed for this analysis were elastic modulus, Poisson ratio, load, contact area dimension, and pavement layer thickness. To mitigate this issue, MSW fly ash was used as a stabilizing agent at varying percentages (5 %, 10 %, 15 %, 20 %, 25 %, and 30 % of the dry mass of the soil sample).According to the AASHTO soil classification, the soil is classified as A-7, has a high free swell, a low soaked CBR value, and a high soaked CBR swell, and does not meet the ERA manual standard for subgrade materials. The laboratory tests shown several improvements in the engineering properties of expansive soil when MSW fly ash were mixed. These improvements included a reduction of soaked CBR swelling, free swell index, plasticity index, specific gravity, optimum moisture content. Additionally, the maximum dry density and soaked CBR values increased. Numerical analysis using Abaqus software focused on vertical deformation of the pavement structure. The results showed that as the percentage of MSW fly ash in form 0 % to 25 % of soil dry weight, the vertical deformation of the pavement structure decreased from 0.84 mm to 0.67 mm. This demonstrates that the addition of MSW fly ash reduced the deformation of expansive sub-grade soil and improved the engineering qualities of pavement structure. In conclusion, the study revealed that the use of MSW fly ash as stabilizing agent effectively reduced the deformation of expansive subgrade soil and improved the engineering qualities of pavement structure.

Assessing the effects of different foundation base shapes on settlement and heaving in expansive clay: numerical analysis

AbstractThis paper investigates the behavior of shallow foundations with different base shapes on expansive soils under various Stresses conditions and different slopes of the base. Expansive soils are soils that undergo significant volume changes due to variations in moisture content, which can cause severe damage to structures built on them. The shape of the foundation base can influence the magnitude and distribution of the soil pressures, as well as the deformation and cracking of the foundation. The paper presents a numerical analysis using a finite element method with Plaxis 3D. The paper also proposes some recommendations for the optimal design of foundation base shapes on expansive soils. The numerical results show that the foundation base shape has a significant effect on the stress and displacement distributions in the soil and the foundation and that some shapes perform better than others in terms of reducing the soil pressures. The paper provides some useful insights for the design and construction of shallow foundations on expansive soils.

A Laboratory Scale Model Analysis of Stock Raft Foundations and Ventilated Foundation Systems Constructed on Expansive Clay Soils

A Laboratory Scale Model Analysis of Stock Raft Foundations and Ventilated Foundation Systems Constructed on Expansive Clay Soils

Enhancing the Mechanical and Microstructural Properties of Low Expansive Clay Subgrade with Vinyl Acetate-Ethylene Polymer Incorporation

Enhancing the Mechanical and Microstructural Properties of Low Expansive Clay Subgrade with Vinyl Acetate-Ethylene Polymer Incorporation

Strength Characteristics of Bentonite Nano Clay Stabilized with Addition of Lime, Fly Ash, and Silica Fume for Soil Environmental Sustainability

The suboptimal engineering characteristics, including low tensile strength and significant compressibility volumetric changes, are the significant challenges faced during the construction of sub-structures in expansive Soil. The instability of the sub-structure leads to the settlement of the structure and compromises its safety and endurance. This paper explores how Bentonite nano clay (BNC) reacts with varying proportions of lime, Fly Ash, and silica fume. The ratios used for these additives were 2%, 4%, and 6%. The Compaction Characteristics and the stress-strain curve are analyzed. Incorporating silica fume into BNC leads to a decrease in both the liquid limit and the plasticity index. Concurrently, this addition increases the plastic limit of the clay. As the percentage of silica fume in the mixture rises, there is a corresponding decrease in the maximum dry unit weight and an increase in the optimum moisture content. Additionally, the introduction of silica fume contributes to an increase in the free swell but also it has an increase in the swelling pressure of clay. These results suggest that silica fume stabilization is an effective method for treating expansive clay.

Microstructural analysis of the pore size and volume distribution of bentonite at two different hydraulic states utilizing different drying techniques

Bentonite, which is known as adsorbent expansive clay, is widely used as a nanoparticle in a variety of applications due to its unique microstructure. Analyzing the pore size distribution is crucial for studying its microstructural behavior. Drying techniques and initial moisture content play a significant role in the microstructural changes of clays. This study aimed to investigate how different drying techniques and initial moisture content influence the pore size and volume distribution of bentonite. The results indicate a correlation between drying techniques and hydraulic states with the microstructural changes observed in bentonite. Pore size distribution analysis reveals distinct differences in micro, meso, and macro-pore volumes depending on the employed drying techniques. Conventional drying methods show significant alterations in pore volume distribution for specimens prepared with moisture content from dry and wet of the compaction curve's optimum water content. Conversely, a separate phenomenon is observed for specimens subjected to direct outgassing without prior drying. It is observed that specimens undergoing outgassing at elevated temperatures exhibit almost similar pore volume distributions between dry and wet specimens. Dry specimens exhibit a higher cumulative pore volume and a greater number of macro pores compared to wet specimens when subjected to a specific drying method. Moreover, specimens subjected to outgassed freeze-drying, oven-drying, and air-drying exhibit significant changes in cumulative pore volume distribution compared to those without outgassing treatment. These findings highlight the importance of employing a standardized drying technique to accurately predict the microstructural behavior of bentonite clay and understand its pore-size distribution.

Unconfined Compressive Strength Testing on Expansive Clay Soils Stabilized with Cement and Lime

Soil stabilization offers an alternative solution to overcome the problem of expansive clay soil characteristics. Unconfined compressive strength tests were conducted on original and expansive clay soils containing cement and lime to investigate the effectiveness percentage of two pozzolan materials. The amount of material stabilization with percentages 2, 4, 7, 10 % cement, and 5% lime for each sample was adopted. The dimensions of the cylindrical sample were 3’’ in height and 3/2’’ in diameter. The relative density was 80% for all samples and sheared at a strain rate of 1 %. The properties of the original expansive clay soil are (w) 40.11%, (γd ) 1.3 gr/cm³, (Gs) 2.59, (LL) 60.05%, (PL) 38.16%, (IP) 21.88% and (qu) 0.61 kg/cm2. The test results indicate that the clay exhibits high plasticity. Based on the results, the effective combination percentage of two pozzolan materials to enhance the characteristics of expansive clay soil is 2% to 7 % cement and 5% lime. However, adding 10% cement and 5% lime causes the UCS value to decrease. The finding of this investigation shows the combination of two pozzolan materials, especially cement and lime, can effectively enhance the UCS values. This enhancement is observed at specific percentages of cement and lime addition. These results underscore the importance of carefully selecting proportions to achieve desired soil stabilization outcomes.

Influence of Mixing Rubber Fibers on the Mechanical Properties of Expansive Clay under Freeze–Thaw Cycles

With the growth of the transportation industry, large volumes of waste tires are being generated, which necessitates the development of effective solutions for recycling waste tires. In this study, expansive clay was mixed with rubber fibers obtained from waste tires. Triaxial tests were conducted on the rubber fiber-reinforced expansive clay after freeze–thaw cycles. The experimental results of the unreinforced expansive clay from previous studies were used to evaluate the effect of mixing rubber fibers on the mechanical properties of rubber fiber-reinforced expansive clay under freeze–thaw cycles. The results demonstrate that the mixing of rubber fibers significantly reduces the effect of freeze–thaw cycles on the shear strength and elastic modulus of expansive clay. The shear strength and elastic modulus of the unreinforced expansive clay decrease markedly as the number of freeze–thaw cycles increases, while the shear strength and elastic modulus of the rubber fiber-reinforced expansive clay do not exhibit any remarkable change. A calculation model of the deviatoric stress–axial strain curves after freeze–thaw cycles was established. The model describes the deviatoric stress–axial strain behavior of rubber fiber-reinforced expansive clay and unreinforced expansive clay under different confining pressures and different numbers of freeze–thaw cycles.

Effect of Drying and Wetting Cycles on the Surface Cracking and Hydro-Mechanical Behavior of Expansive Clays

Expansive clays present serious issues in a variety of engineering applications, including roadways, light buildings, and infrastructure, because of their notable volume changes with varying moisture content. Tough weather conditions can lead to drying and shrinking, which alters expansive clays’ hydro-mechanical properties and results in cracking. The hydro-mechanical behavior of Al-Ghatt expansive clay and the impact of wetting and drying cycles on the formation of surface cracks are addressed in this investigation. For four cycles of wetting and drying and three vertical stress levels, i.e., 50 kPa, 100 kPa, and 200 kPa, were investigated. The sizes and patterns of cracks were observed and classified. A simplified classification based on main track and secondary branch tracks is introduced. The vertical strain measure at each cycle, which showed swell and shrinkage, was plotted. The hydromechanical behavior of the clay, which corresponds to three levels of overburden stress as indicated by its swell potential and hydraulic conductivity was observed. It was found that at low overburden stresses of 50 kPa, the shrinkage is high and drops with increasing the number of cycles. Al-Ghatt clay’s tendency to crack is significantly reduced or eliminated by the 200 kPa overburden pressure. The results of this work can be used to calculate the depth of a foundation and the amount of partial soil replacement that is needed.

Intuitionistic Connection Cloud Model Based on Rough Set for Evaluation of the Shrinkage–Swelling of Untreated and Lime-Treated Expansive Clays

The evaluation of the shrinkage–swelling characteristic of expansive clay is of great significance, but it is a complex problem since the evaluation process involves numerous uncertain factors, such as randomness, non-subordination, and hesitation uncertainties. Here, an intuitionistic connection cloud model has been proposed to address this issue. First, an evaluation index system is established. According to the reliability of interval-valued evaluation indexes, the corresponding cloud numerical characteristic parameters are specified based on the membership interval generated by the intuitionistic fuzzy principle. Moreover, the improved conditional information entropy based on rough set theory is utilized to assign the index weight. Subsequently, combined with the weight, the intuitionistic connection degree of the sample to the classification standard is determined to identify the shrinkage–swelling grade. Finally, a case study on the shrinkage–swelling grade of untreated and lime-treated expansive clays in Hefei Xinqiao International Airport was performed to illustrate the validity and reliability of the model. The results show that the proposed model is reasonable and feasible for the evaluation of the shrinkage–swelling grade of untreated and lime-treated expansive clays.