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Title:Lime treatment to improve frictional resistance and stability of stiff clay slopes
Author(s):Moridzadeh, Mohammad
Director of Research:Mesri, Gholamreza
Doctoral Committee Chair(s):Mesri, Gholamreza
Doctoral Committee Member(s):Stark, Timothy D.; Long, James H.; Fernandez, Gabriel
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Landslides occurring around the world are often associated with substantial damage to human life, infrastructures, and private properties, thus affecting the economy. Introducing lime, cement or other stabilizers to the potential shear zone or along the pre-existing slip surface of reactivated landslides is an alternative to increase the stability and reduce the rate of movement. The effectiveness of lime treatment of soils has been commonly evaluated in terms of increased unconfined compressive strength; however, if the objective of lime treatment is to improve long-term stability of first-time or reactivated landslides in stiff clays and shales, permanent changes in the size and shape of clay particles must be realized to increase drained frictional resistance. Lime-soil reactions that may produce less platy and larger soil particles begin and continue with time under the highly alkaline pH environment. In this study, measurements of pH as an indicator of chemical environment, Scanning Electron Microscopy (SEM) images as a direct measure of particle size, shape and arrangement, Atterberg plastic limit and liquid limit as indirect measures of changes in particle size and shape, and fully softened friction angle and residual friction angle, are used to examine possible mechanisms of lime-soil reactions. The main variables, in addition to soil mineralogy, are soil water content, lime content, and duration of lime-soil reactions. Drained direct shear tests are used for the measurement of fully softened and residual shear strength. Lime improvement of frictional resistance was examined using samples of Chicago clay from Chicago, Brenna clay from North Dakota, and Beaumont clay from Harris County Flood Control District (HCFCD), Texas. Chicago clay is known as an illitic clay, whereas Brenna and Beaumont clays are montmorillonitic clays. Brenna clay contains a small amount of sulfate in its composition, which in reaction with lime produces ettringite; needle-shaped products observed in SEM images. There are similarities between reaction of clay with lime and that with cement. Understanding clay-lime reactions would help in comprehending pozzolanic reactions occurring when cement or other additives are added to clay. The drainage and flood control infrastructure of Harris County include more than 1,500 channels with a total length of approximately 2,500 miles. The HCFCD spends $7-8M each year to maintain channel slopes, Several slope failures in drainage channels in Harris County, Texas, were evaluated pre- and post-lime treatment using the shear strength envelopes determined from the laboratory tests. In addition, the stability of Red River slopes in Grand Forks, North Dakota, and CUP O’Hare reservoir slopes in Chicago, Illinois were analyzed.
Issue Date:2019-04-16
Rights Information:Copyright 2019 Mohammad Moridzadeh
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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