Behavior Of Expansive Soils Research Articles

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.

A laboratory investigation and numerical modeling on fiber reinforced lime and alkaline binder stabilized pavement subgrade soil

The differential settlement and excessive deflection in expansive subgrade soils lead to low volumetric stability upon moisture imbalance and cause severe damage to highway and airport field pavement surfaces. The present paper attempts to strengthen the stability behavior of expansive subgrade soil using an envirosafe alkaline binder (AB) with polypropylene fiber (PLF). AB was produced by combining dry aluminosilicate precursors (steel slag [SS] and sugarcane bagasse ash [SBA]) with a liquid activator (mixture of sodium hydroxide [NaOH] and sodium silicate [Na2SiO3]) in 0.4 water to binder (w/b) ratio. California bearing ratio (CBR) based resilient modulus, shear strength ratio (Sr), and consolidation tests were conducted as performance indicators of expansive subgrade soil reinforced with discrete PLF (0–0.5%) in 6% lime and 6% alkaline binder. The study also proposes the optimal sugarcane bagasse ash-steel slag-PLF dosage in the AB-stabilized subgrade layer. Moreover, mineralogical and morphological studies using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were also carried out to understand the crystalline compounds and micro surface texture of the soil-fiber mixture. It was revealed that AB-fiber-soil exhibits higher interfacial frictional bonding and interlocking density than lime-fiber-soil. Also, 2D finite element analyses were carried out to compare the behavior of subgrade under the influence of vehicular load on the surface. PLF-AB soil mixture shows 72% lower vertical deformation than unstabilized expansive soil. Based on the findings of this study, recommendations for the practical application of stabilizing expansive subgrade soils were proposed.

Assessing the synergistic effects of GGBS and glass fiber on expansive soil behavior using response surface methodology

Assessing the synergistic effects of GGBS and glass fiber on expansive soil behavior using response surface methodology

Studying the Behavior of Expansive Soil Reinforced by Micropiles

Expansive soil is a form of soil that can expand and contract, changing its volume. Montmorillonite, a mineral with the ability to dissolve in water, makes up the majority of these kinds of soils, and by increasing the volume of the soil, it causes the soil to heave. Expansive soils could be a substantial concern for engineered buildings due to their capacity to adjust to seasonal variations by contracting or expanding moisture content. Many researchers focused on soils that were swollen and looked at how they behaved as well as how they could be improved. In this study, the work depends on inserting micro-piles with different depths and configuration widths to investigate which depth and configuration can be obtained to improve the bearing capacity of foundations on expansive soil. The main purpose of this study is to reinforce the expansive soil with micro-piles with different depths (1B, 2B, and 3B) and different configuration widths (under footing only, 1B and 2B). It was concluded that the soil reinforced with micro-piles improved the load-bearing capacity of the expensive soil and decreased the swell pressure. The increasing depth of the micropiles 2B to 3B (B is the width/diameter of the foundation) can increase the bearing capacity by just 6%; therefore, increasing the depth beyond 2B is not beneficial. Also, the increase in width of the configuration of the micro piles from 1B to 2B increases the bearing capacity by just 4%; therefore, the increase in width greater than 1B is not valid. Doi: 10.28991/CEJ-2024-010-01-017 Full Text: PDF

Experimental study of stabilization of soil using nano silica.

The behavior of structures depends on the properties of the soil on which they are constructed. Some problems like settlement and bearing capacity are critical for structures over the expansive soil, the soil sample has been characterized as expansive soil based on swelling test. Stabilization techniques are adopted to enhance the expansive soil behavior and performance of foundation overlying weak soil. This paper focuses on studying the effect of nanomaterials (Nano MgO and Nano Al2O3) with different proportions viz. 0.5%, 1.0%, 1.5% and 2.0% on the properties of expansive soil. The results indicate that swelling potential is reduced with the addition of these nanomaterials and thus making the soil suitable for construction purposes.

Dynamic behaviour of oyster shell powder-modified expansive soil under cyclic loading

This paper systematically studies the dynamic mechanical properties of oyster shell powder (OSP)-modified expansive soil under simulated train loads. A GDS dynamic triaxial test system was used in the study. The axial cumulative strain development and hysteresis curve characteristics of expansive soil with different oyster shell powder particle sizes (dosp=0–0.075 mm, 0.075–0.15 mm, 0.15–0.25 mm, 0.25–0.5 mm, 0.5–1.0 mm, 1.0–2.0 mm), dosages (Fosp=0 %, 3 %, 6 %, 9 %) and cyclic stress ratios (CSR=0.1, 0.15, 0.2, 0.25, 0.275, 0.3) were studied. The results show that when dosp< 0.5 mm, the axial cumulative strain, damping ratio and dynamic resilient modulus of the modified soil are significantly improved with increasing oyster shell powder content; when Fosp= 9 % and dosp< 0.5 mm, the dynamic performance of the modified soil is similar. When Fosp= 9% and dosp= 0.25–0.5 mm, compared with plain soil, the axial cumulative strain decreases by 37.3 %, the damping ratio decreases by 39 %, and the dynamic elastic modulus increases by 29.9 % after 200,000 cycles. When dosp> 0.5 mm, the performance of each dynamic performance index of the modified soil deteriorates compared with that of the plain soil, and the deterioration effect is more significant with increasing oyster shell powder content and particle size. When oyster shell powder-modified soil is used as a subgrade filler for a ballasted track railway with a design speed below 200 km/h, it is recommended to control the content of oyster shell powder as Fosp= 9 % and the particle size of oyster shell powder as dosp= 0.25–0.5 mm. At this time, from the perspective of controlling the postconstruction settlement of the railway subgrade, the cyclic stress ratio CSR should be controlled below 0.2.

Wet-dry cycle of expansive soil stabilized with fly ash and waste foundry sand on bearing capacity and swelling potential

The behavior of expansive soil, which is sensitive to water, makes it susceptible to moisture content changes, resulting in the soil becoming soft during the rainy season and soil shrinkage during the dry season. This research aims to study the effects of the wet-dry cycle on the bearing capacity and swelling potential of stabilized expansive clay soil using two types of industrial waste, namely Fly Ash (FA) and Waste Foundry Sand (WFS), as soil improvement and industrial waste management efforts. The wet-dry cycle is assumed to represent the changes in the environment due to seasonal variations. The wetting cycle is conducted by immersing the soil samples in water, while the drying cycle is achieved by allowing them to air dry at room temperature. The FA content is set at 9% and the WFS content at 15% by weight of dry soil. The California Bearing Ratio (CBR) test is performed after the completion of the wet-dry cycle, while the swelling test is conducted during the wet-dry cycle. Each sample undergoes one, two, and three cycles of wetting and drying. The results showed that the CBR value increased with the addition of FA and WFS. The CBR value of natural soil is 8.89% while the CBR value of soil+9%FA+15%WFS is 16.02%. During the wetting phase, the CBR value decreases with increasing moisture content. After undergoing the third cycle, the CBR value and development potential tend to remain constant.

Discrete particle methods for granular bentonite material simulation

Bentonite clays are strategic materials to ensure the sealing capacity of engineered barrier systems (EBS) in deep geological repositories of high-level radioactive waste. Formerly installed in the form of compacted blocks, in recent years, there has been growing interest in EBS design using granular bentonite materials (GBM) due to improved construction processes [1]. GBM range from the powdered and granulated forms, both natural and obtained from crushed blocks, to compressed bentonite pellets, and the mixtures thereof. The effect of thermo-hydro-chemo-mechanical (THCM) conditions on the evolving gap-filling performance following installation has been investigated in full-scale experiments [2] and in laboratory-scale tests [3], with particular focus on bentonite pellet-powder mixtures [4, 5, 6].&#x0D; Numerical modelling of coupled THCM expansive soil behaviour is widespread using continuum methods, namely the finite element method [7, 8], applicable up to full-scale systems even though at the expense of resolution. At the laboratory scale, discrete particle-based methods accounting for the granular nature of bentonite materials in the early stages of hydration provide insight into pellet shape and local effects on the mechanical behaviour of dry pellet-powder systems as well as hydro-mechanical effects on the swelling capacity of GBM systems.&#x0D; The compressibility of dry pellet packings and pellet-powder mixture samples is modelled by the discrete element method (DEM). This method has been applied to study the swelling behaviour of pellets represented by spherical particles [9]. The DEM is a powerful tool for reproducing complex granular shapes by non-spherical particle surfaces [10] and also with clumps of spheres (Figure 1(a)), allowing to define mixed material and mechanical contact properties within the pellets. The deformation and fissuring of pellets under oedometer compression is tracked using a cohesive particle model [11], including damage for interparticle contacts in tension, which captures deformation associated phenomena such as surface spalling and pellet reorganisation occurring at stress levels below the diametral fracture. In addition, bentonite powder is represented by loose packings of upscaled spheres matching&#x0D; the experimental porosity of the fillings, interacting by a classical linear spring-dashpot contact model resulting in the reduced overall compressibility observed in pellet-powder mixtures [5].&#x0D; Flow through GBM systems is modelled by the new discrete particle-based XMm method [12]. In the XMm, the material is discretised into a set of bentonite units (BU) or particles acting as representative elementary volumes of a homogeneous continuum inside which the mass balance equations are solved at the megastructural (X), macrostructural (M), and microstructural (m) pore levels (Figure 1(b)). Moreover, the mechanical compatibility of the system is obtained from the coupling between strain increments and centroid displacements in each BU, where the contact stress and overlap between neighbouring particles are updated similarly to the DEM approach. The hydro-mechanical problem is posed as a set of ordinary differential equations (ODE) to be solved for each BU, and thus the efficiency of the XMm is a compromise between the typically reduced computational cost of ODE solvers and the number of BU considered. The XMm has been used to simulate the hydration of a powder sample with low heterogeneity [4], successfully capturing the evolution of the displacement field upon saturation in isochoric conditions. This method is applied to reproduce the confined hydration of a heterogeneous pellet-powder system [6]. Assuming 2D axisymmetry, the XMm allows defining different initial material properties in each BU introducing the heterogeneity of the sample. The evolving swelling pressure is reproduced as well as the hydration velocities at the different structural levels, showing the decreasing heterogeneity of the mixture.

Experimental Analysis on Swelling, Shrinkage and Consolidation behavior of Expansive Soils under wetting – drying cycles

Expansive soil get compressed under the applied external loading and by its self-weight, during this loading pore water goes out of the soil mass, called as consolidation and during the increase in temperature of the soil mass, water evaporates and leaves the soil mass, called as shrinkage. In both the cases, volume change occurs in cohesive soil mass. In this study, an attempt is made to criticize the consolidation and shrinkage phenomena to find the settlement of soils. An expansive cohesive soil sample has been taken and tested for basic properties and also tested for shrinkage, swelling and consolidation. Results shows that settlement caused by shrinkage is greater than consolidation, for the given thickness of clay strata and the type of mineral and proportion.

In-situ Creep Behavior of Expansive Soils Based on Pressuremeter Test

In-situ Creep Behavior of Expansive Soils Based on Pressuremeter Test

Understanding the role of Ca2+, Na+ on swelling behaviour of natural expansive soils: a field application perspective

Understanding the role of Ca2+, Na+ on swelling behaviour of natural expansive soils: a field application perspective

ECO-FRIENDLY SOIL STABILIZATION: A COMBINED APPROACH USING LIME AND WASTE EGGSHELL POWDER

&lt;p&gt;In recent years, geotechnical engineers preferred environmentally friendly and sustainable techniques to improve the engineering characteristics of expansive soil. This paper focuses on the comparative study of the enhancement in engineering properties of expansive soil using lime and waste eggshell powder. A series of laboratory tests such as Unconfined Compressive Strength Test, pH test, Free swell Index Test, Swelling Pressure Test, California – Bearing Ratio test and Atterberg’s limit test were performed for evaluating the engineering behaviour of expansive soil with lime and waste eggshell both individually and together. The experimental test results showed that the combined admixtures significantly improve the engineering characteristics of the soil. The maximum value of compressive strength at the inclusion of 9% lime and 12% waste eggshell powder was observed to be 306 kPa. The swell pressure of the treated soil showed up to a reduction till 2.32 at the inclusion of 3% lime and 12% waste eggshell powder. In all the tests, the combined admixtures exhibited greater efficiency when compared to individual inclusion of lime and waste eggshell. Thus, the investigation results confirmed the efficient use of lime and waste eggshell powder at optimum percentages as soil-stabilizing material and made them suitable for field applications.&lt;/p&gt;&#x0D;

Study on Cynodon dactylon root system affecting dry–wet cracking behavior and shear strength characteristics of expansive soil

Expansive soil exhibits remarkable characteristics of water absorption expansion and water loss shrinkage, rendering it susceptible to cracking under the alternating dry–wet environments of nature. The generation and development of cracks in expansive soil can result in catastrophic engineering accidents such as landslides. Vegetation protection is an important approach to stabilizing expansive soil slopes and fulfilling ecological protection requirements. In this study, through indoor experiments and theoretical analysis methods, the effects of Cynodon dactylon roots on the crack development and shear strength of expansive soil subjected to dry–wet cycles were analyzed, and the relationship between the crack development and shear strength decay in root-doped expansive soil was explored. Furthermore, the mechanism of vegetative root system action was elucidated. The results show that the Cynodon dactylon root system exerts a significant inhibitory effect on crack development in expansive soil. The crack indexes of root-doped expansive soil exhibit significant phase characteristics during the process of dry–wet cycles. The crack-blocking and reinforcing effect of the root system becomes pronounced as the root-to-soil mass ratio increases and the root diameter decreased. Moreover, the process of crack development in expansive soil is accompanied by a decrease in soil shear strength. The quantitative relationship between crack development and shear strength decay can serve as a basis for predicting the stability of slope soil. Overall, the results highlight the potential of vegetation-based approaches in protecting slopes with expansive soils and have practical implications for ecological protection and engineering design in areas with expansive soils.

Sustainable Lignin to Enhance Engineering Properties of Unsaturated Expansive Subgrade Soils

New ways to apply sustainable materials, such as biomass components, are essential for reducing dependence on fossil fuels. This work investigated the engineering properties of unsaturated expansive subgrade soils stabilized by bio-based energy coproducts containing lignin. Lignin is a waste by-product of the paper and pulp industry that is frequently burned. Highway subgrade could consume lignin as an environmentally benign, low-cost, and energy-efficient chemical substance for soil stabilization. Swell and shrink behavior of expansive subgrade soils complicates highway construction and causes damage to existing highways. However, research on the hydromechanical properties and volume change behavior of lignin-stabilized expansive soil is limited, and better insight is required into its unsaturated behavior for safe and economical pavement design practices. In this research, a series of geotechnical laboratory tests were conducted to characterize expansive subgrade soils treated with lignin by determining the Atterberg limits, compaction and consolidation behaviors, swelling characteristics, and water retention properties. The mechanisms influencing the changes in engineering properties of lignin-treated expansive soils were further investigated using soil pH, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The study shows that the optimal lignin content contributed to an acceptable degree of soil stabilization. The lignin-based cementing material effectively bonds soil particles together and fills pores, thereby preventing water infiltration into the soil and reducing the swell–shrink potential of stabilized soils.

Laboratory investigations on the behavior of CBR in two expanding soils reinforced with plant fibers of varying lengths and content

Any structure built on soil with poor mechanical and physical properties, such as swelling soil, needs to be reinforced. Previous research has focused on the effects of additives such as lime, cement, and sand on these properties. On the other hand, current technological developments in soil reinforcement are leading to more cost-effective and environmentally friendly engineering solutions. In this context, using plant fibers in civil engineering, especially in geotechnical engineering, is considered a new technique to solve soil problems. This study aimed to investigate the effect of discrete, randomly distributed fibers on the heave of expansive soil. California Bearing Ratio or CBR tests were performed on two types of reworked expansive soils without and with fibers, varying the length and percentage of addition. This paper presents the results of an experimental program on the ability of fibers to inhibit the behavior of expansive soil. Three natural fibers (Alfa, jute, and sisal fibers) were used as reinforcement materials. These fibers were used in different percentages, namely 1%, 3%, 9%, and 18%, with three lengths (L1 = 10 mm L2 = 30 mm, and L3 = 90 mm) respectively. For a specific type of fiber. It was found that the improvement in swelling potential/pressure was a direct function of the length or percentage of fiber addition. The longest fiber is most effective at slowing down swelling to produce the optimum stabilization scenario. 18% has been suggested as the optimal content for all three types of fiber. On the other hand, higher inclusions might be a good option if the compression set is not a key problem. The study provides a solution for dealing with expansive soils before construction begins and is a step toward mitigating the disasters associated with infrastructure on expansive soils.

The Role of Stress States on the Hysteric Behavior of Expansive Soil under Multiple Drying-Wetting Cycles

Expansive soils in the field are typically exposed to cyclic wetting and drying due to climatic fluctuations and subjected to a variety of stress conditions in nature or when used as compacted layers for the construction of hydraulic barriers or waste disposal facilities. The hysteric behavior of the soil-water characteristic curve (SWCC) is a key parameter for understanding, modeling, and interpreting the unsaturated behavior of these soils under such conditions. This study investigates the effect of stress states on the hysteresis behavior of soil-water characteristic curves (SWCCs) for compacted highly expansive clay over a range of matric suction between 0 and 1500 kPa. Two test series were performed, the first test series investigated the effect of stress states on the hysteresis of SWCCs during a single drying-wetting (DW) cycle. The second test series studied the combined effect of stress applied and multiple drying-wetting cycles on the SWCC hysteresis. For the sake of comparison, the overall SWCC hysteresis due to drying-wetting cycles was quantified using the average degree of hysteresis in terms of volumetric water content (ADHθ). Furthermore, contributors to the observed hysteresis were defined using two newly proposed measures; namely, average degree hysteresis in terms of gravimetric water content (ADHw) and in terms of volume change (ADHe*). The outcomes of this study indicate that consideration of stress states on the hysteresis of SWCC for expansive clay is of great importance. The results show a dual trend for the variation of ADHθ with applied vertical stress. Furthermore, multiple DW cycles induced a significant reduction in the hysteresis (ADHθ) under low- and high-stress states up to a certain level of DW cycles, then, no further changes in the hysteresis trend were detected. It was also found that hysteresis loops under a low-stress state were concentric in shape while hysteresis loops for specimens under a high-stress state were non-concentric, with a downward shift in hysteresis loops with the increase in DW cycles.

Understanding the Engineering Behaviour of Expansive Soil Amended with Bagasse Ash and Lime Using Microstructural Analysis

Understanding the Engineering Behaviour of Expansive Soil Amended with Bagasse Ash and Lime Using Microstructural Analysis

Hydromechanical behavior of unsaturated swelling clays: review

Expansive soils are materials composed mainly of active minerals of the smectite family, where montmorillonite is an essential member of that group. These types of soils tend to undergo volumetric changes due to variations in moisture content. Many geotechnical engineering practices, such as dam core design or subgrade compaction, require a thorough evaluation of the response of these soils to determine placement conditions. However, the main problem in evaluating the mechanical response of this type of soil lies in the nonlinear nature, which limits the use of most classical constitutive models that apply the basic rules of elastoplasticity. In this study, an analysis is carried out to understand the hydromechanical behavior of expansive soils in saturated and unsaturated conditions. Direct and indirect physical evidence is presented and discussed to evaluate the hydraulic response of the soil structural elements responsible for these adverse dynamics from a global (expansive phenomena as a whole) and individual (swelling and shrinkage) perspective. Since the response of these soils is hydrostatic dependent, the locus of water movement in porous media is examined, starting from the Richards equation (1931), in order to consider the flow mechanisms in unsaturated media under transient conditions.

Viability of bulk utilization of granite sludge powder (GSP) to enhance the geotechnical behavior of expansive soil

Granite blocks are cut, ground, and polished in the processing industries to achieve the desired dimension and texture. As a by-product of this process, finely powdered granite sludge powder (GSP) is generated. Over the last few decades, extensive research has been conducted in the field of using various industrial by-products to enhance the geotechnical characteristics of poor soils, thereby benefiting both the environment and the economy. The current study seeks to determine whether granite sludge powder can improve the geotechnical properties of expansive soils and be reused in pavement applications. Thus, the effect of different concentrations of granite sludge powder (0%, 5%, 10%, 20%, 30%, and 40% of the dry weight of soil) on the index and engineering properties of black cotton (BC) soil is evaluated. The study reveals that, with addition of up to 40% granite sludge powder to untreated natural expansive soil reduced free swell, Atterberg limits, and optimum moisture content. Whereas the engineering properties such as UCS, dry density, and CBR improved with the addition of GSP up to 30% and reduced thereafter. The maximum CBR value of 19.8 was obtained at 30% GSP concentration relative to the weight of dry soil. According to the test results obtained, granite sludge powder up to 30% can improve expansive soils geotechnical properties and could be used in subgrade applications for low volume roads.

Effect of Metakaolin on the Swelling and Shrinkage Behaviour of a highly Expansive Soil

Chemical stabilization of soil is essential for construction work because it improves engineering characteristics of soil, such as swelling soil stability. The main objective of the research is to investigate the impact of adding Metakaoline (MK) on the behavior of expansive soil to reduce swelling. Different amounts of Metakaoline, such as 2 %, 4 %, and 6 % of the weight of dry soil, are used to prepare the soil specimens. The engineering properties of the soil sample are examined using a variety of laboratory tests (consolidation, swelling potential, and liner shrinkage) original and treated soil at various mixing ratios to determine the swell potential and swelling pressure. The findings showed that the addition of MK has caused a reduction in the swelling reaching about 91% with 4% MK at 14 days, Also, the swelling pressure decreased from 110 kPa to 30 kPa with 4% Metakaolin.