A Semi-empirical Approach-Based Model for Swell Characterization of Expansive Clays (original) (raw)
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Estimation of swelling characteristics of expansive soils with influence of clay mineralogy
Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, 2021
ABSTRACT In the present study, characterisation and quantitative microanalysis were identified for six expansive soils of which one is natural soil, i.e. black cotton (BC) soil and remaining soils were prepared by mixing of BC soil with different percentage of bentonite. The BC soil and prepared soil samples were characterised by the X-ray diffraction (XRD) and scanning electron microscope (SEM). The regular or irregular mixed layers of soils justified by SEM images. There are superstructures whose spacing can simply be described as the ratio of BC soil and prepared soil. d-Spacing was calculated by Bragg’s formula (XRD) which was observed by joint committee on powder diffraction standards card and calculated by Bragg’s equation for h-k-l plane for expansive soils and it was observed that d-spacing decreased with increasing prepared soil combination. Moisture content was taken below optimum moisture content, i.e. 15%, 17% and 20% to determine swelling and swelling pressure and found that montmorillonite mineral affects the swelling characteristics of expansive soils.
Swell and shrinkage characterizations of unsaturated expansive clays from Texas
Engineering Geology, 2013
Expansive soils have long been recognized as problematic because they cause failure to civil structures constructed above them. The main problem of these soils can be attributed to poor understanding of the volume changes caused by moisture fluctuations. Current swell and shrinkage characterization models are limited by both the lack of standardized tests and tests that employ volume changes in uniaxial direction. In the present research, a comprehensive laboratory investigation was undertaken to study the volume change related swell-shrinkage behaviors of five different types of expansive clayey soils sampled from various regions in Texas, USA. Extensive experimental programs consisting of basic, chemical and mineralogical soil properties were first determined. Three-dimensional free swell and shrinkage tests were performed on all soils at various compaction moisture content conditions. Soil water characteristic curves (SWCCs) of all test soils were determined by studying the suction potentials of these soils over a wide range of moisture contents. Volume change measurements of soils showed a good correlation with soil properties, including plasticity and soil compaction properties. SWCC results also showed a clear variation in SWCC profiles of soils with respect to soil plasticity. Overall, a large database of soil properties was developed and is presented here. It includes physical and mineralogical properties, and engineering test results including swell, shrinkage and SWCCs.
Study on Suction Swell Characteristics of Expansive Clays
International journal of engineering research and technology, 2019
The objective of the proposed study is to obtain the relationship between soil suction and swell pressure based on drying soil water characteristics curve. To understand the relation between suction and swell characteristics of clays of high and intermediate permeability detailed laboratory investigations were carried out. The percent swell and swell pressure is low for CI clay than CH clay and are higher for solid state than semisolid state and plastic state. The percent swell of soil compacted for maximum dry density and selected dry of optimum density are lower than that of semisolid state. The swell pressure of clay compacted at maximum dry density and selected dry of optimum density are higher than that of solid state. Air entry value and residual suction value are higher for liquid state than plastic and solid state. The dewatering rate also decreases from liquid state to solid state. The relationship between suction and swell vary as the state of soil varies. The relationship between initial water content and percent swell as well as suction and swell pressure are nonlinear for both CH and CI type of clays. The influence of initial state is dominant for CH type clay than CI type clay.
SWELL-SHRINK CHARACTERISTICS OF EXPANSIVE SOIL: A REVIEW
IAEME PUBLICATION, 2019
Volume changes in expansive soil may manifest in two forms namely swelling or heave wherein increase in volume takes place and compression or shrinkage wherein decrease in volume would occur. Swelling and shrinkage may occur independent of loading, while compression and heave are because of loading and unloading. Construction of building on expansive soil is highly risky due to cyclic shrink-swell properties. This soil type creates many problems to the geotechnical engineers primarily because of repeated change of moisture content. Generally, these types of soils increase its size when they absorb water and reduce its size when they become dry. Type of clay mineral, exchangeable cation type, pore fluid effect, and soil structure are important physicochemical factors responsible for physicochemical interactions on the compressibility behaviour of soils. Swelling characteristic determination on this soil is very necessary in the design of any structure. Swelling characteristics are generally obtained from oedometer tests on undisturbed specimens. Then the soil specimen is inundated with distilled water and swell potential is calculated as the increase in height of the soil specimen divided by the initial height, often expressed as a percentage. In this review paper the swelling and shrinkage characteristics of expansive soil is discussed in detailed.
Presence of swelling soils under the foundations of civil engineering structures particularly lightly loaded structures has caused serious damages around the globe due to their differential up heaving. In this paper, based on the results of swell tests on bentonite mixed clay, correlations for predicting the swelling parameters (i.e., swell potential and swell pressure) have been proposed. Mixing of bentonite into low swelling clay has imparted significant variations in its index properties including activity and plasticity index as well as in its swell potential and swell pressure values. Mixing of bentonite from 0 % to 55% into lean clay (CL) varies its placity index value from 18 to 150 resulting into variation of its activity from 0.62 to 1.87. For the same range of bentonite addition, the swell potential and swell pressure values vary from 2.62% to 12.16% and 94 kPa to 928 kPa, respectively. Based on multiple linear regression analysis of swell and index property test data, correlations between swelling parameters, activity and remolding moisture content for expansive soils have been developed. Experimental data of twenty six (26) swelling soils procured from various sites in Pakistan have been used to validate the proposed correlations. These correlations have predicted the swell potential and swell pressure of these soils within accuracy of +10% and +5%, respectively, in comparison with their experimentally determined values. A comparison of these predictions with couple of well-known published empirical equations has also been made.
International Journal of Research and Analytical Reviews (IJRAR), 2019
Expansive soils expand and shrink after they absorb wet exhibiting moderate to terribly high shrink-swell potential that influences the index properties of soil. Thus swell Potential helps to determine the analysis and style of structures created on expansive soils. The main objective of this review article is formed during this criticism that evaluates expedient methodologies for probably expansive soils and assessment of the techniques used for classification functions. The results of the analysis of revealed techniques disclose that the most effective techniques and so the most effective indicators of potential swell are the liquid limit and plasticity index. Alternatively the important indicator properties in raining order are liquid limit and natural water content combined with shrinkage limit and plasticity index and shrinkage limit and linear shrinkage. It is concluded that the laboratory knowledge are analyzed to work out further properties which can sensitively indicate the degree of potential swell in physical, chemical and typical association of swell characteristic parameters. The soil behavior is predicted by considering the soil state and soil sort connected by the environmental factors specifically initial wet Content, unaltered Dry Density and integrative parameters like Liquid Limit and plasticity Index. From this review, it are often all over to know the importance of combinations of physical/chemical, and mineralogical measurements in classifying the soil vulnerability to swelling and also the quality of swelling potential estimation.
Swell characteristics of natural and treated compacted clays
EJGE, 2008
This study investigates the swell characteristics of a highly plastic clay in its natural state and after this clay was separately treated with potassium and calcium chlorides. Free swell tests were conducted on these three (natural and treated) soils at two different temperatures (26°C and 40°C) This study shows that a linear relationship exists between the percent free swell and the liquid limit for the tested soils at given water content, dry density, and temperature and also shows that these soils are not susceptible to expansion when the liquid limit drops below about 40 % regardless of the initial states of water content and dry density as well as test temperature. This study confirms that the percent free swell may reliably be modelled by a rectangular hyperbolic equation as a function of time and liquid limit. The influence of temperature on the swell potential are observed to be dependent on initial compaction states.
Influence of water density on the water-retention curve of expansive clays
Géotechnique, 2012
There is increasing evidence from researchers on clay mineralogy that the density of water attached to clay minerals may be greater than 1·0 Mg/m3. This fact becomes especially evident in compacted highly expansive clays close to water saturation. This kind of material is being considered in the design of engineered barriers for radioactive waste disposal, because of its sealing and retention properties. From a geotechnical point of view, most of the analyses required to check the performance of the barrier are sensitive to the value considered for the water density. This is the case for the unsaturated flow calculations, which depend on the water-retention properties of the soil. This paper presents, first, a review of measurements performed at microscopic level. A description of the hydration process of expansive clay considering the micro and macrostructure is included. Then a method to obtain an average water density as a function of suction for sodium and calcium bentonites is ...
Swelling Curve in Terms of Effective Stress for Expansive Clays
E3S Web of Conferences
Expansive soils can present an unsaturated state where the soil exhibits volume changes due to both moisture variations that change the state of stresses and moisture variations that interact with its mineralogical characteristics. These special kinds of soils are normally clay type soils that had suffered isomorphous substitution creating a charge imbalance of the clay mineral crystals. This imbalance promotes the trapping of water molecules by the clay particles. It is commonly assumed that a high plasticity index can be an indication of a clay´s high swell potential. However, in arid regions, it is possible to have clays with very high swell potential and low plasticity indexes due primarily to a decrease in the state of effective stress, which will produce expansion of the material. It is common practice to study the swelling characteristics of these soils by performing free-swell tests that can be used for designing removal and replacement backfills or drilled shafts. However, ...