Clayey Subgrade Soils Research Articles

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.

Geopolymer Production From Waste Polyethylene Terephthalate and Glass For Clay Subgrade Stabilization

In this study, the efficacy of Polyethylene Terephthalate (PET) and Waste Glass Powder (WGP) as soil stabilizers was investigated to address the research questions and objectives. It examines the enhancement of mechanical strength of clayey subgrade soils sourced from Ogun state, Nigeria across varying proportions (5% −20%) including the potential cost analysis. Providing experimental insights into soil stabilization using PET individually and in combination with WGP-based geopolymers. Optimal stabilization was achieved at 5% PET, accompanied by 5%-20% WGP, and activated with a 2M NaOH solution. Results demonstrated enhanced mechanical strength with both stabilizers, with the combination of PET and WGP proving the most effective. Specifically, stabilization with 5% PET (1.18mm) WGP geopolymer, activated with 2% NaOH, yielded optimal results, exhibiting UCS values ranging from 180kN/m2 to 320kN/m2, surpassing cement-based stabilization (UCS value: 380kN/m2). Moreover, durability testing revealed significant improvements, with PET+WGP samples displaying a UCS mean of 259.4kN/m2, a weight of 89.67g, and a percent change in mean and weight of −25.79% and −25.86%, respectively, compared to cement-stabilized soil (UCS mean: 408.66 kN/m2, percent change: 2.15%, weight mean: 109.25g, percent change: -25.86%). Furthermore, PET+WGP exhibited a 125% increase in CBR compared to PET alone and a better cost reduction of $6,153,850,000.00 for 100km, highlighting its superior performance and cost reduction. The findings of this study hold significance for informed decision-making in material selection for road pavement works, offering an alternative method and contributing to Sustainable Development Goals and Circular Economy initiatives by advocating sustainable waste management and road infrastructure.

Influence of fibres on the resilient modulus and expansion of clayey subgrade soils

ABSTRACT Expansive clayey soils at the subgrade level of roads and highways in different cities can affect the performance and durability of pavements. This increases the need for maintenance and conservation work, leading to higher operating costs. Traditionally, clayey soils are stabilised by adding lime or cement. However, the handling and use of these materials are restricted in some Latin American countries due to illegal drug production, and obtaining high-quality materials from distant sources can be impractical. The goal of this study is to determine the effectiveness of incorporating fibres in improving the performance of expansive clayey subgrade soils. To achieve this goal, resilient modulus tests and measurements of compacted soil expansion were performed. Two types of fibres were selected for this study: natural Ichu fibre, which is common in the Peruvian Andes, and polypropylene fibre. The soil used was a high-plasticity clay from the city of Pucallpa, to which varying percentages of fibres were incorporated (0.25%, 0.5% and 1%). The samples were prepared with a gyratory compactor to achieve their maximum dry density as obtained with the standard compaction effort. The results indicated that the incorporation of fibres improved the value of the resilient modulus while significantly reducing soil swelling.

Effect Of Water-Fly Ash-Cement Grouting On The Clayey Subgrade Soil Characteristics of The Tuban-Babat Lamongan-Gresik National Road

Effect Of Water-Fly Ash-Cement Grouting On The Clayey Subgrade Soil Characteristics of The Tuban-Babat Lamongan-Gresik National Road

Kaolinite subgrade strength characteristics variation with RBI Grade 81

The shrinking behaviour of clay soil due to moisture variation causes damage to the foundation of structures, residential, commercial structures and embankment construction. To overcome this problem, the soil needs to be treated to improve its strength and durability of the ground. The best technique is stabilization, which enhances the engineering soil properties, upgrades the shear strength, and reduces the consistency limit. In this present study, Kaolinite clayey subgrade soil is stabilized using Road Building International Grade 81 (RBI), and its effects on the strength characteristics of the soil are studied. Compaction characteristics, Atterberg's limits, Unconfined Compression Strength tests (UCS), and Split Tensile Strength (STS) on the soil samples were performed. The same composites are studied for SEM and XRD results to confirm the morphology of the new compounds formed. Compaction factors increased optimum moisture content (OMC), and the maximum dry density (MDD) decreased with RBI Grade 81 to kaolinite. UCS values increased significantly for the clayey subgrade with the addition of RBI Grade 81. RBI Grade 81 at 8% shows an enhanced upgrade in the clay subgrade's strength compared with the natural kaolinite subgrade. Hence, RBI Grade 81 can be recommended as a potential soil stabilizing agent, particularly for clayey subgrade soil.

Effect of Axle Overloading on Pavement Structural Behaviour with Improved Clayey Subgrade Using PET Fibres

Clayey subgrade soils are considered to have a lower bearing capacity, which may develop early pavement failure due to diverse axle loading. To avoid such failure issues, these soils must be treated prior to the beginning of the construction work. In the recent past, soil stabilization with plastic waste has become popular to reduce waste and improve soil behaviour. The current study aimed to use polyethylene terephthalate (PET) waste bottles to improve clayey subgrade soil for pavement construction. The PET fibre content varied between 1% and 5% by weight of the dry soil to investigate its influence on compaction, California bearing ratio (CBR), unconfined compressive strength (UCS), and tri-axial shear strength. The modified soil matrix with PET was further stabilized using Terrasil (0.1%) in order to improve the strength properties of the treated soil with ageing. Overall, the influence of the addition of the PET fibre on the structural behaviour of flexible pavement under diverse axle loading conditions was evaluated using Finite Element (FE) techniques. The pavement model is computationally implemented in ANSYS to study pavement structural behaviour in terms of surface deflection, vertical stress and strain on the subgrade layer, maximum shear strain in the bituminous layer, and tensile strain at the base of the bituminous layer under standard loading and overloading by 1.25 and 1.5 times. The test results indicated that the addition of PET fibres in subgrade soil significantly increases the CBR, UCS, and internal friction angle and decreases the compaction characteristics. The use of PET fibres in subgrade stabilization can result in a significant reduction in pavement thickness. FE analysis results compare pavement rutting performance and show that overloading reduces rutting life.

Strengthening Soft Clayey Subgrade Soil Layer Using Cement Kiln Dust and Palm Kernel Ash Materials

The product materials which are generated from industrial manufacturing are used to enhance the engineering and chemical properties of soil. There are three phases of soil improvement are improvement without the addition of any other material, adding certain materials, and providing reinforcement. This study used materials product from industrial and waste materials as additives to improve the physical properties and strength of clayey soil subgrade under foundation and flexible pavement structure. This study has been investigated the effect of isolated and combined Cement Kiln Dust (CKD) and Palm Kernel Ash (PKA) materials on strength of clayey soil as tested by California Bearing Ratio (CBR) test. Various percentages of CKD and PKA materials were added to clayey soil samples to determine the optimum percent of CKD and PKA. The results showed that CKD and PKA have improved soil strength at the optimum compound percent of CKD content was 8% and PKA was 2% by weight of dry soil.

Displacement Monitoring in Airport Runways by Persistent Scatterers SAR Interferometry

Deformations monitoring in airport runways and the surrounding areas is crucial, especially in cases of low-bearing capacity subgrades, such as the clayey subgrade soils. An effective monitoring of the infrastructure asset allows to secure the highest necessary standards in terms of the operational and safety requirements. Amongst the emerging remote sensing techniques for transport infrastructures monitoring, the Persistent Scatterers Interferometry (PSI) technique has proven effective for the evaluation of the ground deformations. However, its use for certain demanding applications, such as the assessment of millimetric differential deformations in airport runways, is still considered as an open issue for future developments. In this study, a time-series analysis of COSMO–SkyMed satellite images acquired from January 2015 to April 2019 is carried out by employing the PSI technique. The aim is to retrieve the mean deformation velocity and time series of the surface deformations occurring in airport runways. The technique is applied to Runway 3 at the “Leonardo da Vinci” International Airport in Rome, Italy. The proposed PSI technique is then validated by way of comparison with the deformation outcomes obtained on the runway by traditional topographic levelling over the same time span. The results of this study clearly demonstrate the efficiency and the accuracy of the applied PSI technique for the assessment of deformations in airport runways.

Toward improved performance of unpaved roads: laboratory tests and field investigation of a soil-byproduct base layer

ABSTRACT In this study, the performance of two steel slag byproducts is investigated to produce mixtures for base layers of unpaved roads. The basic physical properties including Atterberg limits, grain size distribution, California bearing ratio and expansion tests of eight different mixtures of soil-byproduct are investigated in laboratory to understand the engineering properties of the mixtures. The byproducts are mixed in different proportions from 50% to 80% by weight with a local (clayey) subgrade soil. Subsequently, two selected mixtures are used to build an experimental road section along an unsurfaced road. Results demonstrate that the gradation and strength of the samples satisfy the requirements for base layers. Furthermore, the mixtures are shown to be of low-plasticity at higher byproduct content and non-expansive. Field investigations show that 12 roller passes at the standard Proctor and 14 at the intermediate Proctor are enough to reach 100% of the degree of compaction.

Mechanical Properties of Low Plasticity Clay Soil Stabilized with Iron Ore Mine Tailing and Portland Cement

Due to economical and environmental issues, utilization of mineral wastes, e.g. iron ore mine tailing (IOMT), as road materials can be recommended as a sustainable alternative. In the present study, mechanical properties, as well as resistance to freezing and thawing cycles (F-T) of low plasticity clay soil stabilized with different percentages of Portland cement (0, 6, 9, 12 and 15%) and different IOMT content (0, 10, 20, 30 and 40%) has been investigated. To this end, unconfined compressive strength (UCS), initial elastic modulus (E0), and indirect tensile strength (ITS) at different curing times of 7, 14, 18, and 56 days for different admixtures was determined to select optimum mix design for stabilization of clayey subgrade soil. This study shows that by increasing the percentage of cement, strength parameters such as UCS, E0, and ITS increases while increasing IOMT does not show a specific trend to increase strength parameters. Evaluation of strength parameters at different curing time showed that in short-term curing times (7 and 14 days), iron ore mine tailing has a positive effect on the strength parameters, while in long-term curing times (28 and 56 days), iron ore mine tailing has a negative effect on the strength parameters. In total, it was found that 12% of the Portland cement and 10 to 40% of the IOMT passes the UCS and F-T criteria for stabilization of low plasticity clay soils, while clay soil (without IOMT) requires at least 15% of Portland cement for stabilization.

Estabilización de suelos mediante el uso de lodos aceitoso

This study of soil stabilization emerges as an alternative in road construction to replace the conventional materials used in the granular layers and/or to improve the subgrade of the pavement structures, while taking advantage of the waste from oil extraction, in an attempt to mitigate the negative impacts on the environment. Soils from the Tunja region were used. A granular material and a clayey subgrade soil were characterized and later mixed with different percentages of oily sludge. Different tests were conducted to determine the properties and analyze the possible behavior in the field with each mixture, among them the CBR and resilient modules. It was determined that with the addition of 6% sludge the best results are obtained referring to improving the properties of resistance and plasticity of the granular material and 4% for the subgrade, with curing periods of 26 days.

Experimental Investigation on Strength and Bearing Capacity Improvement of a High Plasticity Clayey Subgrade Soil Using Lime

Limited connectivity and poor infrastructure of roads acts as a roadblocks hampering the socio-economic development of one region. In order to overall development of these regions an effort should be given to cultivate well established road network. But due to scarcity of good quality soil PWD engineers are often forced to build roads over the weak soil which directly affects the strength and durability of the road. It is therefore essential to improve the engineering properties of such problematic soil with suitable stabilization technique as and when encountered. Lime stabilization is one such well known chemical stabilization technique extensively used to improve the poor subgrade condition and it is recommended by several codes in INDIA. This paper attempts to study the effect of lime on strength and bearing capacity improvement of soft clayey soil. A series of UCS and CBR tests are conducted with different percentages of lime (i.e. 3, 5, 7 and 9%) and at different curing period to assess the potential of lime in strength improvement. Test results indicate that strength, stiffness and bearing capacity of the soil is considerably improved after lime amendment. Both unconfined compressive strength (UCS) and California bearing ration (CBR) improved up to 7% of lime beyond that it decreases. The improvement of UCS and CBR is found approx three and five fold as compared to original soil. Underlying mechanisms of this improvement is further scrutinized by microstructural analysis such as X-ray diffraction (XRD), Field Emission scanning electron microscope (FESEM) with Energy dispersive X-Ray Analysis (EDAX). Apparent formation of some new peaks in XRD analysis and change of textural and structural morphology of clayey soils obtained from FESEM confirms the formation of cementitious compounds in the lime stabilized soil.

Resilient modulus of clayey subgrade soils treated with calcium carbide residue

ABSTRACT Use of industrial by-products to improve subgrade soils in flexible pavements is gaining popularity as a sustainable construction practice. Calcium carbide residue (CCR) is a by-product of acetylene gas industry. In this paper, an attempt has been made to evaluate the influence of calcium carbide residue in improving the performance of clayey subgrade soils. The improvement in resilient modulus of two clayey soils (with low plasticity and high plasticity) with the addition of calcium carbide residue is studied by carrying out repeated load triaxial tests. The influence of variation in moisture content on the repeated loading behaviour of virgin soils and CCR stabilized soils is examined. Two regression models (Universal and NCHRP model) reported in literature are found to exhibit very good fit with the experimental data.

Resilient and permanent deformation behaviour of clayey subgrade soil subjected to repeated load triaxial tests

Mechanistic-empirical design of flexible pavement AASHTO practice requires resilient characteristics of sub grade soil. Though the resilient modulus is assumed to account for plastic strain accumulation, some subgrade soils with more fine content undergo excessive plastic deformation under repeated loads even though they have remarkable resilient properties. Hence permanent deformation is also an important parameter which should be considered in the design process. In the present study, permanent deformation behaviour of clayey subgrade soil with intermediate compressibility is studied using repeated load triaxial tests. The influence of confining pressure, moisture content and deviator stress levels on the permanent deformation behaviour is examined. The transition of the soil sample from stable to unstable state can be observed and critical stress levels established with the help of shake down theory. Two regression models reported in the literature, Power law model and VTT model, are used to predict the plastic strains with a number of load cycles and stress levels as the variables.

Integrated geophysical investigation of the causes of road pavement failure along Ibadan-Lagos dual-carriage, Southwestern, Nigeria

An integrated geophysical study has been conducted in a segment of Ibadan- Lagos Dual-carriage road to examine the geological factors responsible for highway failure. Schlumberger Vertical Electrical Sounding (VES) and Very Low Frequency Electromagnetic Method (VLF-EM) to evaluate the subsurface integrity, mapping out the subsurface structural features within the sub-grade soil and delineating the bedrock relief as a means of establishing the causes of road pavement failure of 1300 m stretch of road from Ibadan axis. Results from VLF-EM showed the presence of near surface linear geologic structures from the surface to a depth of 15 m which suggests probable conductive zones that have devastating effects to the foundation of the road pavement (g1, g2 and g3). VES results showed the presence of four geologic layers while fractured basement were observed with resistivity value generally less than 100 Ωm which indicates the presence of the water table. The unstable segment is characterized by low resistivity of the near surface materials and shallowness of the aquifer zone on which the road pavement was constructed. The failure of the road is caused mainly by geologic sequence and structures such as clayey subgrade soil under the road pavement and some suspected geological features such as faults and fractures. Keywords: Lithologic contacts, aquifferous zone, geoelectric section, linear contact, sub-grade soil

Assessment of sulphates effect on pH and pozzolanic reactions of soil–lime–natural pozzolana mixtures

ABSTRACTThe geotechnical properties of subgrade soils may need to be enhanced for appropriateness in pavement construction using mineral additives such as cement, lime (L) and fly ash. An experimental investigation was undertaken to study the effects of sodium (Na2SO4) and calcium (CaSO4·2H2O) sulphates on pH and pozzolanic reactions of soil–lime–natural pozzolana (soil–L–NP) mixtures in order to choose an adequate mixture for pavement subgrade soil stabilisation. The pH was measured for different curing periods with and without sulphates. The results showed that increases and decreases in pH values depend on the type of additive and its amount, type of sulphate and its content, mineralogical composition of stabilised soil and curing period. In addition, the pH parameter can be used as an indicator to track the pozzolanic reactions process. On the other hand, clayey subgrade soils can be stabilised with Lime–Natural Pozzolana (L–NP) mixtures containing any amounts of CaSO4·2H2O which is highly recommended. However, Na2SO4 with a low content has a better effect on the behaviour of these soils but become deleterious when its content is greater than 2%. In general, the addition of sulphates accelerates both the pozzolanic reactions and NP dissolution.

Mechanical Behavior and Sulfate Resistance of Alkali Activated Stabilized Clayey Soil

Clayey subgrade soil requires treatment in order to make the subgrade stable for pavement structures. Treatment of clayey soil i.e. stabilization of clayey soil by cement, lime, and fly ash are established techniques used in geotechnical and highway engineering. Stabilization by alkali activation of fly ash is reported recently but literatures are limited. Present study investigates the stress strain behavior, peak stress and ultimate strain of clayey soil stabilized by slag and slag-fly ash blending by alkali activation. The peak stress as high as 25.0 N/mm2 may be obtained at 50% slags content when 12 molar sodium hydroxide solutions were used. Peak stress, ultimate strain and slope of stress–strain curve of stabilized clay are controlled by Na/Al and Si/Al ratios. Stress–strain response and peak stress of slag and fly ash blended specimen are not governed by Na/Al and Si/Al ratios; rather the behavior is dependent predominantly on slag content.

Remediation of Mud Pumping on a Ballasted Railway Track

Maintenance of ballasted railway tracks is a major cost for railway infrastructure owners. In many developed countries, much of the railway infrastructure is mature and was built for service requirements long since superseded. The increased demands on historic infrastructure can lead to the development or exacerbation of localised trackbed problems that require disproportionate levels of maintenance. Identifying these and applying cost effective remediation has the potential to reduce maintenance spend in the long term. However, it is not always clear what the most cost effective remediation will be. One type of localised maintenance issue is the development of wet beds or wet spots, which can occur where saturated clayey subgrade soils are overloaded and result in the development of mud pumping as trains pass. This leads to the migration of fines into the ballast bed and a deterioration in local track performance. Over time the track overlying the wet bed settles disproportionately more, sleepers become progressively more voided, and train ride quality deteriorates. Maintenance of the wet bed may involve locally digging out and replacing the ballast; however, unless the underlying cause is addressed the problem is likely to recur, requiring repeated localised maintenance interventions. This is costly, reactive and ultimately an ineffective approach to managing the problem. This paper presents a study of a wet bed in the UK, both prior to and after a full track renewal. Transient track deflections during train passage were monitored using sleeper mounted geophones and high speed filming techniques. Loaded track geometry data were obtained from a track recording vehicle. It is shown that local maintenance interventions were generally ineffective, but that a renewal of the top 200mm of the trackbed including placement of a geotextile filter and geogrid appears to have been successful in remediating the problem, at least in the short term.

Assessment of Molding Moisture and Suction on Resilient Modulus of Lime Stabilized Clayey Subgrade Soils

A comprehensive laboratory study was undertaken to evaluate the effects of molding moisture and suction on the resilient modulus (MR) and unconfined compressive strength (UCS) of lime stabilized clayey subgrade soils. Two subgrade soils, AASHTO class A-6 and A-7-6, are stabilized with three percentages (0, 5, and 7 %) of lime on the basis of pH test and used to prepare cylindrical MR samples at three moisture contents: optimum moisture content (OMC), dry state (OMC-2 %), and wet state (OMC +2 %). MR tests on lime stabilized soils are conducted with a modified stress sequence incorporated in the AASHTO T307 procedure based on past literature and laboratory experience gained in this study. Test results revealed that the effects of moisture on MR and UCS values of lime stabilized soils were less than those on untreated soils. MR and UCS values increased due to lime treatment, but improvement varied with soil type and lime dose. A filter paper method was used to determine the total and matric suctions at different moisture states in this study. It was observed that osmotic suction increased to 15 % of the total suction due to lime treatment. Finally, an existing MR constitutive model was revised by incorporating total suction. The revised model was shown to have better predictive capability over existing MR models.

Addition of Lime and Fly Ash to Improve Highway Subgrade Soils

AbstractLaboratory tests have been carried out in order to evaluate the improvement in engineering properties relevant to highway design and construction obtained when clayey subgrade soils are stabilized with lime or fly ash. The experimental program included California bearing ratio (CBR) tests to evaluate the bearing strength of stabilized soils used as working platforms during highway construction. The admixture of lime or fly ash caused an increase in the plasticity limit, while both the liquid limit and the plasticity index of the soils have been reduced. Substantial increases in the California bearing ratio value, higher than those of the soil–fly ash mixtures, have been obtained when the soil samples were mixed with lime. The swelling after a 4-day soaking period has been reduced with the addition of both additive materials. The increase in optimum moisture content acts subsidiarily to the increased CBR value, particularly at high lime or fly ash percentages. An analogous effect has been found for...