Swelling Curve in Terms of Effective Stress for Expansive Clays

In this article, a literature review of statistical models giving the parameters of swelling clay soils in relation to other geotechnical parameters whose determination is easily given. These models were then applied to our database which consists of 35 free swelling tests performed on reconstituted samples. This application has shown that it is difficult to generalize these models to any type of soil. We also proposed specific models in our tests taking into account the increasing of the factors number. The results have show that the pressure correlates better than the amplitude and the inclusion of a higher number's parameters in the model improving the later performance.

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.

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.

Innovative Infrastructure Solutions, 2016

Expansive clays exhibit swelling due to water intake along with spatial variations when the soils are initially aggregated. The resulting differential movements have severely affected civil infrastructure across the Canadian prairies. A large cell was designed, fabricated, calibrated and used to determine the spatial variability in swelling of expansive clays. Observations over a 2-year period indicated uneven vertical swelling and the presence of cracks in the center of the sample. The initial swelling (achieved within 24 h) of about 8 % gradually transitioned into primary swelling and registered a value of 109 % ± 8 % after 2 years. The differential swelling was found to vary by 50 % (from SP = 80 % along the wall to SP = 130 % in the center) after 1 year and by 71 % (from SP = 96 % along the wall to SP = 167 % in the center) after 2 years. Keywords Expansive clays Á Soil aggregates Á Spatial variability Á Large cell Á Swelling potential

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.

Abstraet-The limitations of existing methods for the prediction of swelling behavior of compacted softs are examined. Both the purely theoretical approach and the purely empirical approach are found to be inadequate. The present study is based on a semi-empirical approach in which a model of swelling behavior is developed leading to equations relating swelling potential or swelling pressure of a compacted soil to its plasticity index, clay content and initial molding water content. The model is based on the concepts of the diffuse double layer, modified by introducing empirical constants to account for elastic swelling effects and other limitations involved in the direct application of double layer theory to real soils. The empirical constants are evaluated from the results of experimental investigations carried out on a large number of soil samples representing a wide variation of clay content as well as consistency limits.

Lecture Notes in Civil Engineering, 2019

This paper aims to describe the dependency of the swelling pressure (Ps) of Tebessa clay soils to the conventional soil properties namely; Plasticity index (PI), dry density (d), initial moisture content (W) and carbonate content (Ca). A statistical model, capable of obtaining an indirect estimation of Ps based on these soil parameters, is provided. High correlation coefficient (R 2) of 0.93 demonstrated predictability of swelling, using multiple regression modeling. Although the above-mentioned parameters play important roles in the swelling behavior of the clayey soils, there is not any universally accepted, simple and quantitative method to classify swelling pressure at present. The equation, proposed in this paper, helps the engineers with evaluating soil pressure in practice. In addition, it can be popularized when environment conditions are satisfied for application in field explorations and design of structures over expansive soils.

Vadose Zone Journal, 2014

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.

Engineering Geology, 1999

A simple formalism is presented to model the behaviour of expansive clays. Two levels of structure are considered. The behaviour of the macrostructure follows the model developed for unsaturated materials by Alonso et al. [Géotechnique 40 (3) (1990) 405-430]. The behaviour of the microstructure is adapted from the work of Gens and Alonso [Can. Geotech. J. 29 (1992) 1013-1032] in order to include the possibility of the micropores being partially saturated. Mechanical coupling between both levels of structure are defined through two functions, one for wetting and the other for drying. They express the change in macrostructural void ratio due to a change in microstructural void ratio, and their value depends on the state of compaction of the macrostructure. The general shape of these curves is discussed on the basis of experimental evidence. Phenomena such as the dependency of strain on stresssuction path, accumulation of expansion strain during suction cycles at low confining stress, accumulation of compression strain during suction cycles at high confining stress, strain fatigue during drying-wetting cycles, macropore invasion by expanded microstructure and development of macroporosity during strong drying can be represented. A mathematical formulation of the model is described and its performance finally assessed by comparison with laboratory tests. $ development of reversible swelling strains when vvaunat@etseccpb.upc.es (J. Vaunat), gens@etseccpb.upc.es (A. Gens) suction decreases at low confining stress; 0013-7952/99/$ -see front matter