Expansive Soil Research Articles

Swell-shrink and microstructural response of expansive soil treated with nanomaterials

ABSTRACT Expansive soils like Black Cotton Soil, exhibit numerous engineering hurdles due to their high swell-shrink behaviour, resulting in structural instability. Traditional stabilization techniques often prove inadequate and available nanomaterials are expensive, creating a demand for a cost-effective and eco-friendly stabilizer like nano rice husk ash (nRHA). This study tackles the challenge of stabilizing expansive soil using nRHA, synthesized via two distinct ball milling methods. Various concentrations of nRHA (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) were tested to assess their effectiveness in reducing the swell-shrink behaviour of Black Cotton Soil.r Result indicate that a 0.4% dosage of 2 + 5 hours nRHA (n 2,0.4) significantly decreases the soil’s swell-shrink potential. This treatment triggers the formation of Calcium Aluminium Oxide (CAO) and Calcium Aluminium Silicate Hydrate (CASH) gels, validated by X-ray diffraction (XRD) and Scanning electron microscope (SEM) analysis. This study advances nRHA treatments in enhancing the swell-shrink behaviour of expansive Soil.

Investigation of the Structural Strength of Expansive Soil in a Seasonally Frozen Region

The existence of structural strength in undisturbed soil results in its distinct characteristics compared to remolded soil. Under the influence of freeze–thaw cycles, this difference may easily cause geotechnical disasters in cold regions. This study aimed to analyze and discuss the expression degree and influencing factors of the structural strength of expansive soil. The unconfined compressive strength (UCS) test, high-pressure consolidation test, and microscopic test were performed on expansive soil retrieved from a seasonally frozen region. Moreover, sensitivity parameters, including stress sensitivity (St.qu, St.σk) and strain sensitivity (St.ɛu, St.Cc), were applied to explore the expression degree and influencing factors of structural strength in a seasonally frozen region. The results reveal that the undisturbed samples have better structural connection and particle arrangement than the remolded samples. However, the primary fractures have a certain degrading effect on the strength of the undisturbed soil as influenced by a seasonally frozen region. With the increase in water content and the decrease in density, the expression degree of the structural strength in terms of compressive strength and the ability to resist deformation enhances under the unconfined condition. By contrast, the expression degree increases in strength and decreases in ability under the confined condition. Furthermore, the effect mechanisms of the basic property, particle composition, structural linkage, lateral confinement, and historical role on the structural expression were analyzed.

The Uniaxial Tensile Strength of Compacted Expansive Soils

The Uniaxial Tensile Strength of Compacted Expansive Soils

Ternary medium constitutive model of frozen rubber-reinforced expansive soil

The application of waste rubber for soil improvement is feasible, and the static and dynamic properties of rubber-reinforced soils have been extensively studied. However, the mechanical properties of frozen rubber-reinforced expansive soils have not been effectively studied due to the complexity of multiphase media under the action of multiple fields, and no applicable constitutive models describe them. In this paper, the stress-strain relationship model for frozen rubber-reinforced expansive soils is investigated over a range of strain rates from 0.18% to 0.3% and the following conclusions were obtained: (1) The structural model of the frozen rubber-reinforced expansive soil can be considered a ternary medium model that consists of elasto-brittle bonding elements, elasto-plastic friction elements and elastic friction elements. (2) The stress-strain relationship can be divided into three stages: linear elastic stage, elasto-plastic stage and strain softening (RC ≤ 15%) or hardening (RC = 20%) stage. (3) The rubber content has a greater influence on the stress-strain relationship. When the rubber content reaches 20%, the expression of the stress-strain curve changes from strain softening to strain hardening, at which time the rubber dominates. (4) The maximum shear strength of frozen rubber-reinforced expansive soil is obtained at 10% rubber content.

Effect of Sample Size, Dry Unit Weight, and Hysteresis of Expansive Soil on SWCC and Finite Slope Stability

Effect of Sample Size, Dry Unit Weight, and Hysteresis of Expansive Soil on SWCC and Finite Slope Stability

Laboratory Test and Constitutive Model for Quantifying the Anisotropic Swelling Behavior of Expansive Soils

Expansive soils exhibit directionally dependent swelling that traditional isotropic models fail to capture. This study investigates the anisotropic swelling characteristics of expansive soil with a medium swelling potential through the use of modified oedometric testing. Vertical swelling strains can reach up to 1.71 times that of the horizontal movements, confirming intrinsic anisotropy. A nonlinear elastic constitutive model incorporates vertical and horizontal elastic moduli with respect to matric suction to characterize anisotropy. Three elastic parameters were determined through the experiments, and predictive equations were developed to estimate the unsaturated moduli. The constitutive model and predictive techniques provide practical tools to better assess expansive soil pressures considering anisotropy, offering guidelines for utilization and design. The outcomes advance understanding of these soils’ directionally dependent behavior and stress–strain–suction response.

Utilization of Nano Silica and Plantain Leaf Ash for Improving Strength Properties of Expansive Soil

This study investigates the effect of nanosilica and plantain leaf ash on the sustainable stabilization of expansive soil. This study conducted various strength tests, including Unconfined Compressive Strength (UCS), direct shear, and California Bearing Ratio (CBR) tests, to analyze the enhancement of mechanical properties by adding nano silica and plantain leaf ash. Scanning Electron Microscopy (SEM) analysis was conducted to investigate the interaction mechanism between the soil and the combination of nano silica and plantain leaf ash. Three different combinations of plantain leaf ash were utilized, ranging from 5% to 15%, alongside nano silica ranging from 0.4% to 1.2%. The reinforced soil’s compressive strength, shear strength, and bearing capacity were assessed through UCS, direct shear, and CBR tests. The results demonstrated significant improvements in compressive strength, up to 4.6 times, and enhancements in cohesion and frictional angle, up to 3.3 and 1.6 times, respectively, at 28 days. Moreover, the addition of nano silica and plantain leaf ash led to increased bearing capacity and reduced soil swelling potential, contributing to the overall stability and strength improvement in expansive soil. The SEM test results demonstrate that maximum bonding and compaction occur when 1.2% nano silica and 15% plantain leaf ash are added to the soil.

Evaluation of brown coal fly ash for stabilising expansive clay subgrade: A sustainable solution for pavement construction

Brown coal fly ash (BCFA) is a lower-quality type of fly ash produced through brown coal combustion, and its disposal in landfills raises environmental concerns. This study, for the first time, evaluates the feasibility of using BCFA for stabilising expansive clay subgrade in pavement construction. Various engineering tests were conducted, including unconfined compressive strength (UCS), repeated load triaxial (RLT), soaked California bearing ratio (CBR), direct shear, and shrink-swell tests. The results indicated that adding BCFA increased UCS, resilient modulus, soaked CBR, and cohesion while reducing shrinkage-swell index and shrinkage/swell strain. The highest resilient modulus (82.52 MPa) and soaked CBR (3.41 %) were achieved with 3 % BCFA content. These findings recommend using 3 % BCFA as the optimum content for stabilising expansive clay subgrade. This research fills a gap by assessing the application of BCFA for stabilising expansive clay soil, providing insights for sustainable utilisation of this abundant waste material in construction.

An ensemble framework-based approach for modeling stability of expansive soil slopes: fusion of machine learning algorithms and protection structure disease data.

Slope failures lead to catastrophic consequences in numerous countries, so accurate slope stability evaluation is critical in geological disaster prevention and control. In this study, the type and characteristics of slope protection structure disease were determined through the field investigation of an expansive soil area, and this information is incorporated into the numerical simulations and works to develop prediction models of slope stability. Four base machine learning (ML) methods are used to capture the relationship between protection structure diseases and factor of safety (FOS). Further, with the help of stacked generalization (SG), four ML models are combined, and the final SG model is used to predict the FOS. The results show that ML methods can effectively utilize this information and achieve excellent prediction results. The proposed SG model exhibits superior accuracy and robustness in predicting FOS compared to other ML methods. With FOS as the regression variable, the main feature contributions are slope height (37.05%) > slip distance of retaining wall (25.43%) > expansive force (18.03%) > slope gradient (12.00%); the coupling relationship among features is also captured by the proposed model. It is concluded that the SG method is particularly suitable for slope stability modeling under small sample conditions. Besides, the SG-based model effectively captures the impact of protection structure diseases on slope stability, enhances the interpretability of the ML model, and provides a reference for the maintenance and repair of the protection structure.

The Effectiveness of Fibre–Lime Treatment on the Dynamic Properties of Expansive Soil Under Cyclic Loading

The Effectiveness of Fibre–Lime Treatment on the Dynamic Properties of Expansive Soil Under Cyclic Loading

Prediction of Soil Expansivity with Direct and Indirect Method in Banten Region, Indonesia

Expansive soils are widespread in Indonesia, particularly in Banten Province, causing extensive road damages. The study aimed to predict the soil expansivity of soil subgrade along the damaged road segments in Malingping, Cikeusik-Cibaliung, and Labuan districts. Indirect and direct expansivity predictions were employed to determine soil swelling potential. Indirect expansivity prediction was conducted based on various criteria using the Atterberg limit and grain size distribution. Direct expansivity prediction was conducted using an oedometer apparatus to measure the expansion index according to ASTM D-4829. A dynamic cone penetration test was also conducted to measure CBR values. Various indirect methods showed inconclusive results of swelling potentials, low to very high. The direct method provided more conclusive results, Expansivity Index = 100-167 and swelling values = 9%-18%, thus, categorized as expansive clay (high to very high swelling potential). CBR values were 1.49%-5% which is lower than minimum provisioned CBR (6%).

ENHANCEMENT OF SUB GRADE SOIL BY USING FLYASH AND LIME

Abstract -In India 15% of land is covered by Black Cotton Soil. The presence of montmorillonite clay mineral in the Expansive soil causes Swelling and shrinking properties which leads to major problems in Construction sites. This can be resolved by using soil stabilization techniques which enhances the engineering properties of soil. The soil stabilization is most important for the construction which is widely used in pavements or any other structures on expansive soil. Utilization of industrial waste materials in the improvement of soils is cost-efficient and eco-friendly method. In the present study an experimental investigation is taken to know the Geotechnical Characteristics of Expansive Soil with the Combination of FLYASH and LIME. In this study soil is mixed with the different proportions of (10%,20%,30% & 40%) FLYASH and (2.5%,5%,7.5%,10%,12.5% & 15%) LIME. The strength gained by soil is investigated by conducting California bearing ratio test & it is also calculated to reduce the thickness of the layer. The maximum dry density increased from 1.38g/cc to 1.54g/cc. The CBR un soaked test value enhances from 1.01% to 6.49% respectively Key Words: Black Cotton Soil, Fly ash, Lime, Compaction, maximum dry density, CBR

Dynamic Evolution of Desiccation Cracks and Their Relationship with the Hydraulic Properties of Expansive Soil

Dynamic Evolution of Desiccation Cracks and Their Relationship with the Hydraulic Properties of Expansive Soil

Enzyme-Induced Carbonate Precipitation Using Yellow Soybean for Eco-Friendly Treatment of Expansive Soils

Enzyme-Induced Carbonate Precipitation Using Yellow Soybean for Eco-Friendly Treatment of Expansive Soils

Mechanism of physicochemical effect on the shrinkage of expansive soil

Mechanism of physicochemical effect on the shrinkage of expansive soil

Study on the relationship between matric suction, unconfined compressive strength, and uniaxial tensile strength for compacted expansive soils

Study on the relationship between matric suction, unconfined compressive strength, and uniaxial tensile strength for compacted expansive soils

Sustainable Geotechnics: Harnessing Bagasse Ash and E-Waste for Improving Soil Performance

This study addresses the prevalent issue of expanding soils in India, which exhibit a propensity to shrink and swell in response to changes in moisture content. Because of their high porosity and poor permeability, expansive soils can seriously jeopardize a structure's ability to support its weight. This study was aimed to use industrial waste like Bagasse ash and processed E-waste in a different ratio. Locally available soil from Sultanpur, Uttar Pradesh, was considered for experimental investigation. First optimum Bagasse ash content from different ratio (10%, 20%, 30% and 40%) by weight of soil is determined and then E-waste in different ratios (2.5%, 5% and 7.5%) was blended in soil. To determine enhancement in soil strength various test like California Bearing Ratio, Unconfined Compressive Strength was done. Optimum Bagasse ash content was determined as 15% and E-waste was 7.5%. Results from the experimental test indicate that the addition of E-waste combined with Bagasse ash improves soil strength in terms of CBR and UCS values. These test results will be helpful in the development and design of pavements and road construction in rural areas.

A PINN-based modelling approach for hydromechanical behaviour of unsaturated expansive soils

Hydromechanical behaviour of unsaturated expansive soils is complex, and current constitutive models failed to accurately reproduce it. Different from conventional modelling, this study proposes a novel physics-informed neural networks (PINN)-based model utilising long short-term memory as the baseline algorithm and incorporating a physical constraint (water retention) to modify the loss function. Firstly, a series of laboratory tests on Zaoyang expansive clay, including wetting and drying cycle tests and triaxial tests, was compiled into a dataset and subsequently fed into the PINN-based model. Subsequently, a specific equation representing the soil water retention curve (SWRC) for expansive clay was derived by accounting for the influence of the void ratio, which was integrated into the PINN-based model as a physical law. The ultimate predictions from the PINN-based model are compared with experimental data of unsaturated expansive clay with excellent agreement. This study demonstrates the capability of the proposed PINN in modelling the hydromechanical response of unsaturated soils and provides an innovative approach to establish constitutive models in the unsaturated soil mechanics field.

Microstructural Transformations and Prediction Models of an Expansive Soil Subjected to Simulated Rainfall Conditions

The pore size distributions of an expansive soil under different simulated rainfall conditions were studied using nuclear magnetic resonance (NMR) techniques. Four sets of treatments with different rainfall intensities (light, moderate, heavy, and rainstorm) and durations (0.5 d, 1 d, 2 d, and 3 d) were designed to analyze the effects of rainfall on the microstructure of the expansive soil. Results show that with increasing rainfall duration, micropores gradually form and develop, enlarge, and interconnect in the soil, eventually forming stable seepage channels. Under light and moderate rain conditions, the proportion of micropores gradually decreases, while the proportions of mesopores and macropores gradually increase. Under heavy and rainstorm conditions, the proportion of micropores sharply decreases and then stabilizes, while the proportions of mesopores and macropores increase. With increasing rainfall intensity, the dominant pore size and porosity both initially increase and then stabilize. A quantitative relationship model between pore size, porosity, and rainfall conditions is established and the fitting effect is good. This study shows that rainfall alters the microstructure of expansive soils, which stabilizes after dynamic equilibrium. This provides a theoretical basis for predicting and controlling the engineering behavior of expansive soils under different rainfall conditions.

Behavior of Stiffened Rafts Resting on Expansive Soil and Subjected to Column Loads of Lightweight-Reinforced Concrete Structures

An approach to estimate the behavior of stiffened rafts under column loads of a lightweight-reinforced concrete structure resting on expansive soils is presented in this paper. The analysis was conducted using the computer program SLAB97, which estimates the 3D distorted mound shape using the finite difference method by solving the transient suction diffusion equation in 3D and computing the corresponding soil movements. The interaction between the stiffened rafts and the 3D distorted mound shape is then analyzed using the finite element method. The SLAB97 program has been validated by comparing its results with the results of others that were shown to be valid. The goal of the study is to make the expansive soil structure interaction models that the previous researchers proposed more logical. Assuming the worst initial 3D distorted mound shapes of the two cases of edge heave and edge shrinkage, an upper-bound solution is obtained. Using the two scenarios of edge shrinkage and edge heave, the program was utilized in a parametric investigation to examine the impact of various parameters on the behavior of stiffened rafts on expansive soils. These parameters include the stiffening beam depth, the maximum differential movement of the distortion mound shape, and the raft dimensions. The behavior of the stiffened rafts subjected to concentrated column loads is concluded to be similar to that of the stiffened rafts subjected to uniform and perimeter line loads in both cases of distortion modes, with regard to the shape of raft deformation and distribution of the bending moments; however, the values of the design parameters such as maximum deflection, maximum differential deflection, and maximum moments are entirely different in these two situations.