Now showing 1 - 10 of 18
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    Evaluating Soil Shrinkage Behavior Using Digital Image Analysis Process
    (01-01-2022)
    Sharanya, A. G.
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    Heeralal, M.
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    In this paper, the shrinkage behavior of silty clay soil widely found in Warangal is characterized under free evaporation condition over a wide range of suction. As a part of the research evaluation, a comprehensive laboratory test program was framed and conducted on the samples collected from Warangal. Slurries of soil samples were subjected to desaturation by evaporation, and the change in the sample dimension was captured with camera still images and Vernier caliper. The captured images were processed and used for quantifying the overall volume change. The shrinkage behavior was represented as soil shrinkage curve (SSC), and the curve exhibited three zones. The proportional or normal shrinkage was dominant with volume of water lost from the pores equaling the volume change in the sample. The structural and residual shrinkage phase indicated the loss of water from both inter- and intra-aggregate pore spaces with gradual increase in time. The study showed the existence of bimodal porosity in low plasticity soil and also discusses the reliable efficiency of the proposed experimental procedure to study the shrinkage behavior of soils with low plasticity.
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    Influence of Footing Size on Reinforcement Geometrical Parameters
    (01-01-2022)
    Venkatesh, B.
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    The load-bearing capacity of the reinforced sand bed depends on the optimum geometrical parameters of the reinforcement layer. This paper presents the effect of the size of the footing (D) on optimum geometrical parameters of the reinforcement, that is, placement depth of the first reinforcement layer (u) and the vertical spacing between the reinforcement layers (h). The jute geotextile reinforcement layer was used for the present model tests. All model tests were conducted using 50 mm diameter circular footing in a steel tank having an inner dimension of 450 mm × 450 mm × 350 mm. In each test, sand was placed at a relative density (Rd) of 70%. Finally, the present test results are compared with the plate load tests of jute geotextile reinforced sand beds using footing diameter (D) 150 mm. The size variation factor for two different diameters (D) of footings is 3. The test results show that the values of optimum geometrical parameters of the reinforcement are not much varying with the respective size of the footing (D). In comparison, the variation with the respective size of the footing is relatively higher for optimum vertical spacing of the reinforcement (h) than the optimum placement depth of the first reinforcement layer (u).
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    Swell-Shrink Behaviour of Lime Pile and Lime Slurry-Treated Expansive Soil
    (01-01-2022)
    Kumar, K. S.R.
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    Expansive soils in the field are subjected to swelling and shrinkage due to seasonal moisture variations. Most of the previous studies on swell-shrink were carried out by direct mixing of stabilizer with soil and very few studies have been carried out on swell-shrink behaviour of expansive soil stabilized through permeation. Hence, in the present study, an attempt is made to study the swell-shrink behaviour of expansive soil through laboratory tests using lime slurry (LS) and lime pile (LP) techniques and the two results are compared. In laboratory the LS were permeated through the central hole of expansive soil in the desiccated state, whereas, the LP was installed in compacted expansive soil. Undisturbed soil specimens were collected from LP and LS-treated expansive soil in the test moulds after a curing period of 30 days for evaluation of swell-shrink behaviour at a radial distance of 1.5d (where d = diameter of central hole) and at depths of 0–90 mm and 200–290 mm for LS and LP-treated soils. The study shows that in LS-treated specimens the volume change increases with an increase in number of wet-dry cycles for the specimen taken at a depth of 0–90 mm, which shows the loss of cementation bonds. Whereas, LS-treated samples taken at a depth of 200–290 mm and LP-treated samples collected at a depth of 0–90 mm and 200–290 mm did not show any improvement in controlling the swell-shrink behaviour of expansive soil.
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    Effect of Salt Solution on Engineering Behaviour of Soil
    (01-01-2022)
    Senapati, Swagatika
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    The response of any soil structure depends on the interaction of clay flakes, water and variety of minerals mixed in the water. Soil containing various minerals may change its geotechnical properties when undergoes both static and cyclic loading. Distilled water is generally not used at the field for any kind of construction works. This paper discusses the compressibility characteristics of marine clay by varying pore medium chemistry. This paper also articulates the change in static and cyclic behaviour of clayey soil mixed with sodium chloride solution. To examine this behaviour, a set of unconfined compressive strength and cyclic triaxial tests were conducted on slurry consolidated samples. Three different strain amplitudes (0.3, 0.7 and 1%) and a constant effective confining pressure of 150 kPa were used in the study for determining cyclic properties. A consistent trend was observed for the set of data which shows an increment in secant modulus values with the increase in pore fluid concentration. The change in electrolyte concentration makes a substantial contribution for enhancing the stiffness properties of the soils.
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    A Critical Review on Stabilisation of Expansive Soils with Compensating Materials
    (01-01-2022)
    Ashok Kumar, T.
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    Expansive soils are mostly found in semi-arid and arid regions, and these soils suffer significant volume change when exposed to seasonal moisture fluctuations. Further, this volume change may cause extensive damages to the engineering structures and also the cost of damages increases every year. Practicing geotechnical engineers used different treatment methods to enhance the engineering performance of these soils. However, the placement of compensating materials in expansive soil deposits was found to be attractive for shallow stabilisation due to its construction feasibility and economic aspect. Extensive research has been carried out for the past 60 years for understanding the mechanisms of compensating materials in controlling the volume change of expansive soils. The engineering solutions to these soils consider various factors like the thickness of expansive soil, swell pressure, active zone profile, and properties of compensating material. This article reviews some of the essential aspects of the physical and engineering properties of different compensating materials and also the placement conditions followed in practice.
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    Effect of induced osmotic suction on swell and hydraulic conductivity of an expansive soil
    (01-01-2019)
    Julina, M.
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    Compacted expansive soils are widely used as engineered barriers in waste contaminant applications like landfills, brine ponds, and nuclear waste disposal sites. These liners are designed for very low hydraulic conductivity (<1 × 10−7 cm/s). Percolation of chemical waste or leachate results in physicochemical changes in compacted expansive soils which increases the hydraulic conductivity. This paper brings out the changes in swelling behavior and hydraulic conductivity of compacted expansive soil induced with osmotic gradients using NaCl and CaCl2 solutions. Multiple identical soil specimens placed in oedometer assemblies were inundated with distilled water, 0.4 and 4 M NaCl (monovalent cations), and 0.4 and 4 M CaCl2 (divalent cations) salt solutions and allowed to swell under a surcharge pressure of 12.5 kPa. Void ratio–water content plots were also traced during swelling process. Falling head permeability tests were conducted on swollen soil specimens in rigid wall oedometer permeameters under a hydraulic gradient (i) of 20. The experimental results showed that the swell potentials reduced and hydraulic conductivity increased with the increase in induced osmotic suction.
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    Effect of Remoulding Water Content on Hydraulic Response of a Compacted Expansive Soil
    (01-01-2023)
    Julina, M.
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    The microstructure of compacted expansive soils differs depending on the remoulding water content and compaction dry density. In particular, along the standard Proctor compaction curve, the expansive soil compacted at water content less than the optimum water content has relatively larger macropores in comparison to the expansive soil compacted at water contents greater than the optimum water content. These changes in microstructure not only influence the hydraulic conductivity but also the infiltration rates during the swelling process of compacted expansive soils. Therefore, this paper brings out the effect of remoulding water content on the infiltration rates during swelling process and hydraulic conductivity at the end of swelling process of a compacted expansive soil. The oedometric-infiltrometer test arrangement was used to determine the hydraulic response, in terms of infiltration rates and hydraulic conductivity, upon inundation of the compacted expansive soil specimens remoulded with water contents corresponding to dry and wet side of optimum water contents at the same standard Proctor compaction dry density. As expected at the end of swelling process, the swell magnitude and hydraulic conductivity were relatively higher for the clay specimen compacted at dry of optimum water content. In addition, the infiltration test results showed that the time needed for the outflow (i.e. permeation flow) to occur and attain a steady state condition was comparatively less for the compacted clay specimen compacted at dry of optimum water content than at wet side of optimum water content. The changes in dry density and water content during the swelling process of compacted clay specimens were also traced.
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    Preface
    (01-01-2019)
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    A Study on Pore Size Distribution of Compacted Expansive Soils
    (01-01-2023)
    Ramesh, Sabari
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    Compacted expansive soils, characterized with very low hydraulic conductivity and good contaminant retention capacity, have been widely used as barriers in landfills. They exhibit a double porosity structure with discrete interaggregate pores (macropores) and intra-aggregate pores (micropores) when compacted at optimum and dry of optimum water contents. The distribution of these macropores and micropores varies for different expansive soils depending on their grain size distribution and compaction characteristics, and thus, an in-depth study is necessary. This paper focuses on pore size distribution analysis using X-ray computed tomography (X-ray CT) and mercury intrusion porosimetry (MIP) tests on four expansive soils collected from different parts of Tamil Nadu, India. X-ray CT test gave the 2D image slices from top to bottom for all the specimens, and the acquired CT images of each soil specimen were segmented to separate the pores from the soil solids. The most probable threshold numbers for image segmentation were obtained using a newly developed methodology. The threshold numbers obtained decreased with increase in coarser fractions present in the soils. The thresholded binary images illustrated the pattern of larger pores in different expansive soils considered for the study. The MIP results showed a lower volume of macropores and a higher volume of micropores for soils with more clay content and higher dry density. A general insight into the range of macropores and micropores size distribution of compacted expansive soils with different gradation and compaction characteristics was achieved.
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    Effect of Sulfate Contamination on Compaction and Strength Behavior of Lime Treated Expansive Soil
    (01-01-2019)
    Raja, P. Sriram Karthick
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    Lime is the most commonly used chemical admixture for the treatment of the expansive soils. But the intrusion of sulfate contaminant into the lime treated soil will always results in deterioration of the treated soil. The intrusion of sulfate occurs through acid rains, effluent from tannery industries or mine wastes, intrusion of sea water, construction waste, intrusion of leachate from solid waste fills and sulphate rich groundwater. Therefore, this paper aims at bringing out the effect of sodium sulfate (Na2SO4) solution on the compaction and strength behavior of the lime treated expansive soil. Further, the effect of compaction delay and curing period on the sulfate contaminated lime treated soil is also brought out in this paper. Lime contents of 2.5 (initial consumption of lime (ICL) −1%), 3.5 (ICL) and 4.5% (ICL +1%) were used in this study. The sulfate contamination was limited to 5000, 10000 and 20000 ppm. The experimental results showed that the sulfate contamination decreased the maximum dry density and optimum moisture content of the lime treated expansive soil. Further, the intrusion of sulfate solution into the lime treated expansive soil decreased the strength of the lime treated expansive soil.