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The engineering properties of expansive soils are conventionally improved through the use of additives such as fly ash, lime, and chemical additives. Such soils are often referred to as stabilized or modified or treated expansive soils. The soil-water characteristic curves (SWCC) of two expansive soils from Texas were measured both in natural and s...
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... fibers are used to enhance tensile strength of soils and to promote recycling of fibrous materials. The physical characteris- tics of both polypropylene and nylon fibers are summarized in Table 3. These fibers are not affected by the presence of salt content in soils, biological degradation, ultraviolet degradation, and high temperature conditions see Table 3. ...
Citations
... Expansive soils are prevalent in arid and semi-arid regions globally [1], [2]. These soils typically demonstrate moderate to high plasticity, along with low to moderate strength and pronounced swelling and shrinkage characteristics [3]. Moisture fluctuations profoundly influence both the mechanical and hydraulic properties of such soils, especially those prone to swelling and shrinkage. ...
The objective of this study was to assess the impact of chemical stabilization on slope stability using water retention test data. The analysis focused on hypothetical expansive soil with a 10 m height and a 34° angle. Two critical unsaturated hydraulic properties were considered: (1) soil water retention curve and (2) hydraulic conductivity function. Chemical stabilizers were introduced at varying percentages relative to cement content, with silica fume (SF) partially replacing portions of the cement. The influence of stabilizers on slope stability was evaluated by examining changes in the factor of safety (FOS) with different stabilizer concentrations. Generally, the FOS increased with higher cement content, with further improvement observed when cement was partially replaced by silica fume. Additionally, the addition of silica fume enhanced water retention capacity, as evidenced by altered pore pressure distribution and water table levels post-rainfall infiltration.
... Likewise, the physical properties of unsaturated soil take on the form of a nonlinear function of suction, which can vary from zero to a million kilopascals depending on the climatic conditions [16]. The behavior of an unsaturated soil sample is primarily influenced by its soil water characteristic curve (SWCC), which shows the correlation between the amount of water in the soil pores (measured in terms of volumetric or gravimetric water content, saturation ratio, etc.) and the soil matric suction [17][18][19]. For a better understanding of the behavior of unsaturated soils, various researchers [20][21][22] have explored the variation of soil parameters along the wetting/drying path of SWCC. ...
The relationship between the soil water characteristic curve (SWCC) and the mechanical behavior of unsaturated soil is imperative and has been well investigated. However, the correlation between elastic wave velocity along the wetting and drying paths of SWCC is largely unknown due to the nonavailability of a standard experimental setup for such a purpose. An ordinary triaxial apparatus has been modified for laboratory assessment of SWCCs under different K o stresses, along with the measurement of shear and compression wave velocities in due course. The main aim of the study is to draw SWCC, wave velocity characteristic curve (WVCC), and a Poisson’s ratio characteristic curve (PRCC) and to establish the phenomenon that these curves possess hysteresis. The Poisson’s ratio was obtained indirectly by measuring Vp and Vs. Three soil samples with relative densities of 85%, 56%, and 39% were prepared and placed in a modified triaxial test apparatus under wetting and drying cycles. The test results showed that the newly developed apparatus is accurately capable of measuring SWCC. Owing to the similarity in the shape of wave velocity and Poisson’s ratio, response to SWCC, WVCC, and PRCC are drawn. The phenomenon of stress history and the effective stress of the soil affected the behavior during wetting and drying paths.
... High suction does not necessarily imply high swelling. Expansive clays stabilized using cement or lime can show very high suction but low swell potential [21,41,42]. It is common in the literature to find prediction models that estimate the swelling pressure, swell potential, compressive strength, etc. using the SWCC. ...
The major problematic soils in semi-arid regions include expansive soils and collapsible soils. These two types of soils cause problems and are hazardous for buildings when moisture is introduced following a dry or semi-dry season. In order to assess the risk and damage likely to occur, a protocol of investigation needs to be considered by geotechnical engineers to quantify and assess the possible heave or collapse that may occur. The characterization and prediction of unsaturated soil behavior in semi-arid areas can now be enabled following the advancement of unsaturated soil mechanics. Heave is associated with the wetting of expansive soils, while excessive settlement or the sudden loss of support may occur when water is introduced to collapsible soils. This work calls for more than one parameter for the assessment of problematic soils to avoid misleading predictions based on a single test. This study presents an investigation of two sets of soil samples obtained from semi-arid areas in Saudi Arabia known for their collapsible or expansive nature. Tests under controlled suction and variable effective stress were conducted. The air entry values, inflection points, and residual points were established and compared for the two problematic soils. A series of oedometer tests was conducted for typical soils, and settlement and collapse were measured and assessed. The swell potential for the tested clays varied from 4% to 22%. It is possible to integrate the data from the soil–water characteristic curve (SWCC) and compressibility tests with any project specification and applied stresses to produce reliable recommendations for the construction and protection of structures in hazardous soils.
... The modification of the natural soil is carried out to assess the effect of the treatment method on different plasticity index soil. The research shows that the 30% BA (by dry weight of soil) content can be considered the optimum percentage for soil reinforcement [38,39]; therefore, the 30% BA content was used in this research. The Atterberg's limit, compaction, free swell index, and grain size distribution tests are conducted on natural and modified clayey soil. ...
Microbially induced calcite precipitation (MICP) has emerged as a promising and environmentally friendly technique to ameliorate unfavorable soil conditions. However, the durability of biotreated clay under freeze–thaw cycles, crucial for road pavement applications, remains inadequately investigated. This research aims to evaluate the effectiveness and long-term performance of biostimulated MICP in improving the engineering properties of expansive clayey soils. The study encompasses both macroscopic and microscopic analyses of untreated and biostimulated soils. Plasticity, strength, mineralogical composition, and chemical characteristics are thoroughly examined. Mechanical tests, including unconfined compressive and split tensile strength assessments, are conducted to evaluate the strength of the biocemented specimens. Additionally, chemical analyses such as pH, electrical conductivity, and calcite content are performed to study the changes in chemical properties. Microstructural examination allows for an in-depth understanding of the structural modifications. Biocemented specimens are subjected to repeated freeze–thaw cycles (2, 4, 6, 8, and 10 cycles) to assess the durability of the treated soils. The study investigates the evolution of properties after each cycle, addressing concerns related to long-term sustainability and performance. The results demonstrate that the biostimulated MICP treatment significantly enhances the calcite content of the treated specimens, exhibiting up to 205% increase, which directly correlates with improved unconfined compressive and split tensile strength. Furthermore, the distribution of calcite content in the biotreated samples is analyzed to provide insights into the uniformity of the biocementation process. In conclusion, the findings underscore the efficacy of the MICP technique for enhancing the strength and stability of expansive clayey soils under freeze–thaw conditions. The study reveals its potential as an eco-friendly alternative for road pavement applications without adverse effects on the natural soil ecosystem. This investigation contributes essential knowledge toward the practical implementation of biostimulated MICP in civil engineering projects, offering sustainable solutions for soil improvement in the field of geotechnical engineering.
... On the other hand, the presence of sulfate ions (SO4 2-) in lime-stabilized soil leads to the formation of ettringite mineral, which is responsible for severe damages observed in road pavements, foundations and infrastructures founded on them (e.g. Mitchell, 1986;Baryla et al., 2000;Puppala et al., 2003Puppala et al., , 2006Puppala et al., , 2009Celik and Nalbantoglu, 2013). These damages depend on the type of additive and its amount, the mineralogical composition of the stabilized soil and the type of sulfate and its amount (e.g. ...
The use of lime in sulfate-bearing clayey soils has historically caused structural damage to infrastructures due to the formation of an expansive ettringite mineral. In this paper, a research was conducted to study the effectiveness of natural pozzolana (NP) for providing better stabilization of sulfate-bearing soils. Compaction and free-swell potential tests were first performed on lime-stabilized grey and red clayey soils (GS and RS) containing different contents of added sodium and calcium sulfates (2, 4 and 6% Na2SO4 or CaSO4·2H2O). Then, the same tests were repeated by adding 20%NP. The test results indicated that the presence of 4% and 6% Na2SO4 in the soil resulted in an abnormal increase in the swell potential of both lime-stabilized GS and RS. The X-ray diffraction (XRD) results confirmed the growth of the ettringite mineral responsible for this higher swell potential. However, the use of 8% lime with 20%NP in stabilizing sulfate-bearing clayey soils produced significant improvements in the optimum moisture content (OMC) and maximum dry density (MDD), as well as in the swell potential. The addition of 20%NP into the lime-stabilized GS and RS eliminated the harmful effect of Na2SO4. In addition, for 120-day curing period, the use of 6% CaSO4·2H2O was found very effective by reducing the swell potential of NP-lime-stabilized GS and RS from 7.33% to 0.4% and from 2.79% to 0.2%, respectively trips. KEYWORDS: Clayey soils, Mineral additives, Sulfates, Compaction, Swell potential, Stabilization.
... However, the presence of sulfate in the stabilized soil caused the formation of the expansive ettringite mineral, which is responsible for damages observed on the infrastructures such as cracks and expansion [1,[18][19][20][21][22][23][24][25]. These damages have been found in dependent on the type of the additive used and its amount, the type of sulfate and its amount and the soil nature [15,17,[26][27][28][29][30][31]. ...
... In addition, in 2010, Ayyappan et al. [43] studied the influence of PF on the engineering behavior of soil-fly ash mixtures used as materials for road construction where they observed that the addition of PF considerably improved the UCS of soil-fly ash mixtures and the optimum dosage rate of the PF was identified as 1% by dry weight of soil-fly ash mixture. The same findings have been found by several researchers when using synthetic fibers in combination with lime for stabilizing finegrained soils [20,[44][45]. For example, in 2012, Pradhan et al. [46] investigated the effect of random addition of PF on strength of cohesive soils where they observed that 0.8%PF content (20 mm length) provided the highest soaked CBR value, increasing the CBR value by three times compared to the control soil. ...
This paper aims to assess the behavior of the unconfined compressive strength (UCS) of polypropylene fiber (PF) reinforced natural pozzolana-lime-stabilized expansive grey clayey soil (GS) contaminated by sulfates. Lime (0–8%), natural pozzolana (NP) (0–20%), and PF (0–3%) by dry weight of soil were used. GS was contaminated by different sulfate contents (0-6%) and UCS was assessed at various curing periods (7–120 days). Results showed that adding 8% lime alone or with 20% NP considerably improved UCS. Including 1% or 2% PF as reinforcement without sulfates in lime-stabilized GS transferred stress from GS to PF due to bonding. However, increasing PF beyond 2% formed lumps, reducing contact and friction coefficient, thus decreasing UCS. This means that the optimum PF dosage was found to be 2%. The UCS of GS increased with PF content up to 2% and then decreased. The UCS significantly increased with higher calcium sulfate content and curing period due to observed cementing agents in X-ray diffraction (XRD) and scanning electron microscopy (SEM). Adverse effect of ettringite mineral on UCS caused by sodium sulfate addition was suppressed with the combination of 20% NP and 2% PF in lime-stabilized GS. Binding forces from lime and NP resisted to ettringite expansion. Sensitivity of UCS to sulfate effect was more pronounced with sodium sulfate than calcium sulfate. In addition, NP–PF mixture in lime-stabilized GS was more effective, improving the strength of expansive soil, especially with sodium sulfate. In conclusion, reinforcement of NP-lime-stabilized expansive soils with PF is an effective method.
... This is because water has difficulty reaching the pockets of unsaturated clay, and clay powder has a higher compression index than clay lumps. Expansive clay is a typical unsaturated soil, and its basic properties-that is, its swelling, shrinkage, and fissure properties-can be greatly affected by water content [14][15][16][17]. Consequently, the repeated uneven swelling and shrinkage of expansive clays under the strong alternating action of drying and wetting can induce disasters, including slope erosion, collapse, and landslides. ...
Expansive clay is one of the most widely distributed soils in the world. Due to its rich content of strongly hydrophilic minerals—such as montmorillonite—expansive clay exhibits substantial swelling and shrinkage properties, and overconsolidation. The formation process of undisturbed expansive clay has a long and complicated geological history and innumerable drying–wetting cycles, resulting in the formation of special internal structures. In this study, the mud-to-natural-consolidation deposition process was simulated using a saturated mud-remolded sample preparation device, and then, mud-remolded soil under a certain consolidation pressure was prepared. Subsequently, the effects of the stress history and drying–wetting cycle on its mechanical properties and microstructure were examined through uniaxial consolidation compression experiments, K0 consolidation experiments, and pressure plate experiments of undisturbed soil, mud-remolded soil, and a drying–wetting cycle sample. The results showed that the mud-remolded soil completely broke the natural structure of the undisturbed soil, with the structural characteristics of the remolded soil being restored to a certain extent after the drying–wetting cycle. This not only reduced the void ratio of the soil sample, but also changed its compressibility and water retention characteristics, revealing the role of atmospheric drying–wetting cycles in the natural overconsolidation state of expansive clay and providing a theoretical basis for understanding their overconsolidation characteristics.
... Expansive soils are foundation material that alters volume due to changes in soil moisture [5,6]. These type of soils are typically found in the world's dry and semi-arid regions. ...
Model footing tests were conducted on two types of footings having aspect ratio (L/B) equals to 1, and 2 resting on single and two layered soil with a geogrid layer placed at the interface of two layered soil. The effect of the upper soft clayey layer stabilized with molasses, waste foundry sand, and lime over medium dense sand was studied by varying the thickness ratio (h/B) of upper layer (h/B = 0.8, 1.2, 1.6, 2.0). The reinforcement effect was investigated by adding geogrid layer of varying width ratio (b/B = 0, 2, 3, 4) at the interface between upper soft/stabilized clayey layer and lower medium dense sand layer. In order to validate the results of the model plate load tests, the bearing capacity behaviour of footings with aspect ratios (L/B) of 1 and 2 was calculated using the finite element method (FEM)-based ABAQUS software. The results of model plate load tests shows that the ultimate bearing capacity of square and rectangular shaped footings at h/B = 1.6 and b/B = 3 was optimum when compared to other thickness ratios (h/B) and width ratios (b/B). This is because the above soft clayey soil was stabilised with optimum amount of additives and placement of a geogrid layer at the interface. Further, upon comparing the pressure settlement behaviour curves generated using model plate load tests and ABAQUS software, a close agreement was found, with numerical results rising slightly upwards.
... Al.,207). The "n" value of a lime-treated soil sample increases as the percentage of lime increases, meaning that the addition of lime results in a more uniform pore size distribution (Puppala et al., 2006) and a faster rate of desaturation than a natural soil sample that has not been treated. The effects of lime treatment on the values of "m" are found to be insigni cant. ...
The engineering behavior of natural untreated and compacted lime-treated expansive soils, which typically exist in a state of unsaturated condition, can be better-explained using concepts from unsaturated soil mechanics. The soil water characteristics curve (SWCC) is the key unsaturated soil property for obtaining unsaturated soil property functions (USPFs). However, there are limited studies on the effect of lime on the SWCC of lime-treated expansive soils. This study investigated the effect of lime on the SWCC of lime-treated expansive soils. The drying portion of SWCCs for untreated natural soil and lime - treated soil samples with three different lime contents (3%, 6% and 9%) with 7 days of curing were studied. The SWCCs were determined by using pressure plate apparatus in the suction range of 0–1400 kPa. The shrinkage curve (SC) was also determined to evaluate the change in volume of the different soil samples. The experimental results indicate that SWCC is affected by lime treatment and there is a change in the SWCC parameters and in the shape and position of SWCC as the percentage of lime is changed. The SWCC of the lime-treated soil samples show a higher rate of desaturation as the lime content increases. The Air Entry Value (AEV) and residual water content of lime-treated soil decreases with increase in percentage of lime and the SWCC shifts towards the left side as the AEV decreases. The differences in AEV obtained from gravimetric water content based SWCC (w-SWCC) and degree of saturation-based SWCC (S-SWCC) for the lime-treated soil samples are small when compared to the untreated natural soil sample.
... Soil water characteristic curves (SWCCs) are useful for illustrating how compaction conditions, index properties, and mineralogy affect the unsaturated hydraulic conductivity properties of clay barrier soils and can be used when modelling flow and transport. SWCC has proven to be a valuable conceptual and interpretative tool by which the engineering behavior of unsaturated soils such as flow, strength and volume change behavior can be understood and predicted (Puppala et al., 2006). Soil suction, Ψ , affects the properties of an unsaturated soil to a great extent and hence its measurement is important for modelling its engineering behavior. ...
A laboratory investigation was carried out on tropical black clay (an expansive soil also known as black cotton soil because cotton plant thrives well on it) treated with up to 12% bagasse ash by dry weight of soil. Specimens were prepared at optimum moisture content and compacted using British Standard light or Standard Proctor (relative compaction = 100%) to evaluate its effectiveness when used in waste containment application. Soil-bagasse ash mixtures were assessed to determine their soil water retention behaviors by curve fitting methods using the two most common soil water characteristics curve (SWCC) models, developed by van Genuchten and Brooks-Corey. The unsaturated hydraulic conductivity values decreased with higher bagasse ash content and matric suction but were less than 1 x 10-9 m/s required for a liner material.
