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Evaluation Of The Rate Of Secondary Swelling In Expansive Clays Using Centrifuge Technology
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Book Synopsis Evaluation of the Rate of Secondary Swelling in Expansive Clays Using Centrifuge Technology by : Jasaswee Triyambak Das
Download or read book Evaluation of the Rate of Secondary Swelling in Expansive Clays Using Centrifuge Technology written by Jasaswee Triyambak Das and published by . This book was released on 2014 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expansive soils are characterized as having high amount of clay minerals such as smectite, which lead to swelling during wet seasons by absorbing water and shrinking during dry seasons owing to moisture loss by evapotranspiration. The soil volumetric changes due to moisture fluctuations cause extensive damage to civil engineering structures, namely pavements, retaining walls, low rise buildings and canals founded on such soils. The primary swelling portion of the swell curve has been studied in significant details in previous studies. However, there is a dearth of literature concerning the secondary swelling phenomenon in expansive clays, which has also been observed in experimental studies. While it may be argued that the magnitude of secondary swelling is significantly less as compared to primary swelling, the characterization of the rate of secondary swelling is relevant for fully characterizing the swell potential of the soil. The rate of secondary swelling has been used to predict the long-term swelling of expansive soils. Conventional laboratory swell tests may take over a month for specimens to demonstrate secondary swelling behavior. A centrifuge based method has been recently developed at The University of Texas at Austin to achieve this objective in multiple specimens, and within less than a day. The effects of soil fabric, soil type, relative compaction, molding water content, gravitational gradient, and infiltrating fluid, on the rate of secondary swelling, are thoroughly investigated in this thesis. Four different expansive clays found widely in and around Texas, namely - Eagle Ford Clay, Tan Taylor Clay, Black Taylor Clay and Houston Black Clay, have been used in the study. Based on this extensive experimental evaluation, it may be concluded that secondary swelling behavior could be explained by flow processes associated with the bimodal pore size distribution in expansive clays. The rate of secondary swelling was found to increase with increasing molding water content and increasing compaction dry unit weight. The experimental results revealed that clays with a flocculated structure (compacted dry of optimum) demonstrate rapid primary swelling but exhibit less swelling in the secondary region, as compared to clays with a dispersed structure (compacted wet of optimum). The slope of secondary swelling showed a decline with increasing gravitational gradient. The rate of secondary swelling showed evidence of upward trend with an increase in the plasticity index and clay fraction of the soil. It was observed that soils which exhibit higher primary swelling also demonstrate higher secondary swelling.
Book Synopsis Characterization of the Swelling Behavior of Expansive Clays Using Centrifuge Technology by : Nicolas Alejandro Rivas
Download or read book Characterization of the Swelling Behavior of Expansive Clays Using Centrifuge Technology written by Nicolas Alejandro Rivas and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental techniques with emphasis in centrifuge testing were implemented to characterize the swelling behavior of expansive clays. This research consisted in three self-contained sections related to the study of different aspects of expansive clays. The first research component focused on the implementation of a qualitative mineralogy analysis performed using x-ray diffraction to determine the main clay minerals in an expansive soil. The analysis was performed on the clay-sized fraction of the soil and samples with preferential and random orientation were used in the analysis. Vacuum filtration was used to produce oriented samples in order to maximize the intensity of the diagnostic basal spacing of the clay minerals, and samples were subjected to different treatments to produce changes in the basal spacing or crystalline structure of the clay minerals to facilitate their identification. The second research component examined the effect of the coarse fraction on the swelling characteristics of expansive soils using a centrifuge-based approach. Vertical strains at the end of primary swelling were evaluated for different proportions of coarse fraction by volume. It was found that the magnitude of vertical strains at the end of primary swelling decreased with increasing coarse fraction. It was concluded that the swelling depended uniquely on the ratio between the volume of soil solids of the fine fraction and the volume of voids. Additionally, when correcting the initial void ratio of the specimens to account for this, the relationship between vertical strains at the end of primary swelling and initial void ratio for the soil mixtures defines a unique linear trend with the baseline material. The third research component examined the potential vertical rise at three field sites in Central Texas. Method 6048-A was applied to evaluate the PVR of three field sites using direct measurements of the swelling characteristics of soils sampled at each location. Project-specific data was generated in a relatively short time using this centrifuge-based method. The results obtained demonstrated the need for testing of project-specific samples, as a significant variation in PVR was observed in Site 2 and 3 between boring locations, while less variation between borings was found in Site 1
Book Synopsis Characterization of the Swelling Potential of Expansive Clays Using Centrifuge Technology by : Jeffrey Albin Kuhn
Download or read book Characterization of the Swelling Potential of Expansive Clays Using Centrifuge Technology written by Jeffrey Albin Kuhn and published by . This book was released on 2010 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: The characterization of the swell potential of expansive clay is complicated by the fact that traditional swell testing methods require an excessive amount of time for specimens to swell to their maximum heights. As a result, the practicing engineer has typically referred to correlations between swell potential and index properties rather than directly measuring swelling in a laboratory experiment. The purpose of this study is to evaluate an alternate testing method using a geotechnical centrifuge in an attempt to decrease the time required to evaluate the swell potential of expansive clays so that expermientally obtained swelling properties may be obtained within a reasonable time period. This study includes an experimental program involving a series of tests in which compacted clay specimens are flown in a cetrifuge and their heights are monitored as water infiltrates into them.
Book Synopsis Characterization of Expansive Clay Behavior Using Centrifuge and Field Evaluations by : Christian Philip Armstrong
Download or read book Characterization of Expansive Clay Behavior Using Centrifuge and Field Evaluations written by Christian Philip Armstrong and published by . This book was released on 2018 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Subsequent to the development of a centrifuge-based test methodology at the University of Texas at Austin, an extensive research program was conducted to quantify the parameters that govern the swelling behavior of expansive soils and to correlate field measurements of heave and moisture fluctuations with predictions from laboratory testing. The overall research was grouped into five self-contained research components. The first research component examined the effect of the initial conditions in centrifuge soil samples on the magnitude and time-history of swelling. The centrifugation of soil specimens was found to not affect the magnitude of swelling, further validating the centrifuge technique as practical and accurate. The second research component examined the effect of soil fabric on the swelling of laboratory-reconstituted and field-sampled clay specimens. Soil fabric was found to affect the time-history of swelling for laboratory-reconstituted specimens and to affect both the time-history and magnitude of swelling for field-sampled specimens. These results can be attributed to the field-sampled specimens containing a higher amount of peds and micro-void features, as revealed using scanning electron microscope micrographs. These micro-void features are removed during soil homogenization in the laboratory-reconstituted samples. The third research component examined the heterogeneity on a regional and local scale of two clay soils commonly found in Central Texas. The results indicated that soil samples derived from geologically older parent material tended to swell more than soils derived from geologically younger parent material and that the method of soil sampling affected the magnitude of swelling. The fourth research component examined the field behavior at a site involving an expansive soil subgrade and was instrumented using moisture content and suction sensors. Moisture fluctuations were found to be significant regardless of the pavement surface, and soil-water retention curves were found not to vary significantly with depth. The heave measured at the site was less than that predicted by centrifuge test results due to volumetric strains and desiccation cracks. The final research component examined the large-scale swelling behavior of a column test, prepared to represent a field site. Results from the large column test were compared to the heave predicted using centrifuge test results and the previous field site. The large column was found to behave similarly to the predictions from centrifuge test results, but the infiltration occurred over a longer time frame than the field site. The difference in infiltration rates between the large column and field site was attributed to desiccation cracking at the field site. Overall, the five research components involving expansive soil behavior indicate that the field monitored swelling can be predicted using laboratory centrifuge tests when properly accounting for initial conditions, soil fabric, and spatial variability.
Book Synopsis Quantifying Using Centrifuge of Variables Governing the Swelling of Clays by : Trevor Meade Walker
Download or read book Quantifying Using Centrifuge of Variables Governing the Swelling of Clays written by Trevor Meade Walker and published by . This book was released on 2012 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Austin, Texas consists of highly expansive soils that have caused failures in many structures. Minimizing the detrimental effects of expansive soils on structures requires that the swelling of these soil(s) is quantified accurately, efficiently, and timely. A testing procedure was developed to directly measure soil swelling using centrifuge technology by Plaisted, 2009. This testing procedure was developed in order to reduce the test duration while generating more swelling data relative to conventional tests that directly measure swell. However, the new procedure was incapable of obtaining in-flight swell data, resulting in the need to develop a procedure to directly measure swell during centrifugation. The objectives of this study were to update the testing procedure developed by Plaisted, 2009 by incorporating the use of an in-flight Data Acquisition System (DAS) that would produce accurate and repeatable results; and use the updated testing procedure to quantify the effects of compaction conditions on swelling for three expansive soils in the Austin area (Eagle Ford Shale, Houston Black Clay, and Taylor Clay). A DAS consisting of linear position sensors, analog to digital converters, JeeNode Arduinos, and an accelerometer was developed and installed within the centrifuge. Specimens were compacted at various water contents, and densities, and subjected to different g-levels. The effects of g-level, compaction water content, compaction dry unit weight, and soil type were determined by comparing the 34 hour swell percentages for the compacted specimens. The results of this study showed that in-flight monitoring of clay swelling could be successfully implemented in a comparatively small centrifuge, and that the data collected from the DAS was accurate and repeatable. Swelling of tested soils was found to be sensitive to changes in water content around optimum, with specimens compacted wet of optimum swelling less than specimens compacted dry of optimum. A 6% increase in relative compaction was found to negligibly affect the swelling. Finally, variations in confinement and compaction conditions were found to have a greater effect on swelling for soils that are more expansive in nature compared to soils less expansive in nature.
Book Synopsis Implementation of Centrifuge Testing for Swelling Properties of Highly Plastic Clays by : Jorge G. Zornberg
Download or read book Implementation of Centrifuge Testing for Swelling Properties of Highly Plastic Clays written by Jorge G. Zornberg and published by . This book was released on 2013 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel centrifuge-testing device was developed for characterization of expansive soils, which are the source of major pavement design and maintenance problems across the state. Specifically, testing protocols were developed for use of a small centrifuge device to provide direct measurement of the vertical swelling of clays. In this test, soil samples are subjected to water infiltration during a comparatively short testing period. The centrifuge approach is well suited for pavement design because it provides not only one data point for a single normal stress but the entire relationship between vertical strains and vertical stresses. This feature represents a significant advantage over conventional swelling tests, which are prohibitively long; in addition, each conventional test provides the vertical strain for one vertical stress. Consequently, this approach is particularly well suited for use with the Potential Vertical Raise (PVR) approach. The objective of this project is to quantify the benefits and implement the new centrifuge technology for characterization of expansive clays in Texas. This research team will achieve this objective by implementing the laboratory procedure developed as part of Research Project 0-6048 using multiple clay sources, developing a spreadsheet with swelling curves (vertical strain versus normal stress) for relevant high-plasticity clays in Texas, incorporating the use of swelling curves obtained using centrifuge technology into the PVR methodology, and developing training material that includes examples of practical problems for calculation of the PVR using actual swelling curves and actual subgrade profiles.
Book Synopsis Potential Vertical Rise of Lime-treated Expansive Clays Using Centrifuge Technology by : Karly Ann Summerlin
Download or read book Potential Vertical Rise of Lime-treated Expansive Clays Using Centrifuge Technology written by Karly Ann Summerlin and published by . This book was released on 2018 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expansive soils are prevalent throughout Central Texas and can cause extensive damage to pavements and other lightweight transportation projects. Methods of directly quantifying soil swell potential are often prohibitively time-consuming, and indirect methods that correlate swell to soil index properties are often based on limited empirical data and ignore variances in soil mineralogy that can significantly affect swell. Soil stabilization or modification, using additives like Portland cement or lime, is often utilized to mitigate the effects of expansive soil. In particular, the Texas Department of Transportation (TxDOT) recommends lime treatment for highly plastic soils below many transportation projects. However, many common design procedures do not directly measure the swell potential of the lime-treated soils and rather rely on methods like the Eades-Grim pH test to determine dosage. Additionally, design procedures do not often include a method for determining project-specific treatment depths. This research seeks to develop a procedure for directly quantifying the swell of lime-treated soils such that a project-specific treatment depth and dosage may be prescribed. Centrifuge tests performed on Eagle Ford clay were used to assess the effects of the testing procedure on swell results. It was determined that mellowing lime-treated soil samples did not significantly affect their swell potential but did increase soil workability. Additionally, curing of lime-treated soil samples decreased swell for samples treated with 4% by dry mass hydrated lime after curing for at least 6 weeks, but curing for any time did not decrease swell for samples treated with 2% hydrated lime. It was concluded that lime-treated swell testing could be optimally performed on uncured samples that were allowed to mellow for 12-24 hours to maximize workability. The reduced testing procedure for directly calculating an untreated and lime-treated soil potential vertical rise (PVR) recommends obtaining 3 data points across a representative range of stresses for each distinct layer of untreated soil in a given stratum, which is fit to a semi-log linear curve. One data point is used for each lime dosage to be tested, and the approximation of a unique soil swell pressure is used to produce a semi-log linear stress-swell curve from each of these points. The area under each curve for the stress range in question is then used to calculate the PVR of a soil profile. PVR analyses on two sites from San Antonio in Bexar County, Texas show that the assumption of log-linear stress-swell curves and the approximation of a constant swell pressure return PVR calculations that are similar to those calculated from stress-swell curves that require more parameters and more data points to propagate.
Book Synopsis Characterization of the Swelling Properties of Highly Plastic Clays Using Centrifuge Technology by : Jorge G. Zornberg
Download or read book Characterization of the Swelling Properties of Highly Plastic Clays Using Centrifuge Technology written by Jorge G. Zornberg and published by . This book was released on 2009 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Soil Suction Approach for the Evaluation of Swelling Potentials of Expansive Clays by : Ching-Hua Mou
Download or read book Soil Suction Approach for the Evaluation of Swelling Potentials of Expansive Clays written by Ching-Hua Mou and published by . This book was released on 1981 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Centrifuge Testing of an Expansive Clay by : Michael D. Plaisted
Download or read book Centrifuge Testing of an Expansive Clay written by Michael D. Plaisted and published by . This book was released on 2009 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expansive clays are located world wide and cause billions of dollars in damage each year. Currently, the expansion is usually estimated using correlations instead of direct testing as direct testing is expensive and often takes over a month to complete. The purpose of this study was to determine if centrifuge technology could be used to characterize expansive clays through direct testing. Testing was performed in an centrifuge permeameter on compacted specimens of Eagle Ford clay. A framework was developed to analyze effective stresses in centrifuge samples and methods were proposed to determine the swell-stress curve of a soil from centrifuge tests. Standard free swell test were also performed for comparison. The swell-stress curve determined by centrifuge testing was found to match with the curve found from free swell tests after correcting for differences in testing procedures. The centrifuge tests were found to be repeatable and required several days for testing rather than weeks.
Book Synopsis Prediction of Swelling in Expansive Clays by : Robert L. Lytton
Download or read book Prediction of Swelling in Expansive Clays written by Robert L. Lytton and published by . This book was released on 1970 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Engineering Evaluation of Expansive Clays by : Lee Arthur Sulzberger
Download or read book Engineering Evaluation of Expansive Clays written by Lee Arthur Sulzberger and published by . This book was released on 1971 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Fabric on the Swelling of Highly Plastic Clays by : Christian Philip Armstrong
Download or read book Effect of Fabric on the Swelling of Highly Plastic Clays written by Christian Philip Armstrong and published by . This book was released on 2014 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expansive soils are extremely problematic in transportation projects, and significant research has been done into examining the effect of moisture content changes and index properties on the swelling of soils. However, little has been reported on the effect of soil structure, or fabric, on swelling. The purpose of this study is to examine the effect of the soil fabric on swelling while, at the same time, validating a new set-up for a centrifuge testing program developed over the course of the project to allow for testing of undisturbed specimens. Testing to examine fabric was performed using two methods at the same effective stress, the conventional swelling test, ASTM D4546, and a new double infiltration approach in a centrifuge, on specimens of the Cook Mountain clay which were either compacted in the testing set-up or trimmed into cutting rings from soil compacted via ASTM D698, the Standard Proctor test. Specimens were compacted either dry of optimum to create a flocculated soil structure or wet of optimum to create a dispersed soil structure. Specimens were tested at their as-compacted moisture content or at a moisture conditioned moisture content to remove the effect of the initial moisture content. The results show that soils with a dispersed structure tended to swell more, over a longer time frame, and with a higher amount of secondary swelling in relation to soils with a flocculated structure when tested using the same initial moisture content. The strong influence of the initial moisture content on swelling was also verified. Further, soil specimens prepared at a comparatively high dry density for a given fabric and initial moisture content were found to swell more than soils prepared at a comparatively low dry density. The new centrifuge set-up, involving submerged specimens, was validated and was found to produce similar swelling results as those obtained from the ASTM D4546 tests. In addition, the new centrifuge approach was found to be more expeditious and results in less secondary swelling than the conventional ASTM approach.
Book Synopsis Recent Developments in the Swelling Model of Expansive Clays for Pavement-Heave Calculations by : Moshe Livneh
Download or read book Recent Developments in the Swelling Model of Expansive Clays for Pavement-Heave Calculations written by Moshe Livneh and published by . This book was released on 2012 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The prediction of pavement heave necessitates knowledge of the swelling-pressure characteristic (the swelling model) of the clay stratum under consideration, data that are usually obtained from laboratory tests on undisturbed clay specimens. It is demonstrated that a general swelling model equation should be employed that predicts the percentage of swell under a given vertical pressure exerted on clay characterized by the following parameters: (a) the liquid limit, (b) the ratio between the in situ moisture content and the plasticity limit, and (c) the in situ dry density. The development of this general equation is described by applying the Excel-solver analysis to 352 local test results, yielding preferable results to those stemming from a previous analysis that utilized the multiple linear regression method. Together with employing the general swelling model, an adjustment for any specific given condition is performed by conducting linear regressions (a simple one and a zero-intercept one) with the local test results and the general swelling model. Finally, the paper outlines guidelines for choosing the most relevant of the three calculated models.
Book Synopsis The Mechanics of Swelling in Expansive Clays by : Andrew A. Porter
Download or read book The Mechanics of Swelling in Expansive Clays written by Andrew A. Porter and published by . This book was released on 1977 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Swelling Behaviour of Unsaturated Expansive Clays by : S. Williams
Download or read book Swelling Behaviour of Unsaturated Expansive Clays written by S. Williams and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Comprehensive Dissertation Index by :
Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1984 with total page 904 pages. Available in PDF, EPUB and Kindle. Book excerpt:
