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Journal ArticleDOI

Effect of hydraulic gradient on swell and hydraulic response of desiccated expansive soil–an experimental study

TL;DR: In this article, the authors investigated the effect of initial hydraulic response during the initial stage of wetting in compacted clay liners and found that the cracks in liners act as preferential flow paths and affect the hydraulic response.
Abstract: Desiccation cracks in compacted clay liners act as preferential flow paths and affect the hydraulic response during initial stage of wetting. This paper investigates the effect of initial hydraulic...
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Book ChapterDOI
01 Dec 2022
TL;DR: In this article , 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 was brought out.
Abstract: 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.
Journal ArticleDOI
TL;DR: In order to study the influence of different clay contents on the fractality of red clay, specimens having four different water contents were prepared as discussed by the authors , and the cracking characteristics of the specimens were observed at 20 °C and 60 °C. Image J software was used to measure and calculate the crack area, crack ratio, crack length and width of each sample.
Abstract: In order to study the influence of different clay contents on the fractality of red clay, specimens having four different water contents were prepared. The cracking characteristics of the specimens were observed at 20 °C and 60 °C. Image J software was used to measure and calculate the crack area, crack ratio, crack length and width of each sample. The test results showed that the development of cracks in red clay could be divided into three stages: crack generation, crack development and crack stabilization. The clay particle content, temperature and water content have significant effects on crack development, and from the test analyses, it was determined that for construction in the Guilin area, it is necessary to pay attention to drainage protection.
References
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Journal ArticleDOI
TL;DR: In this paper, the authors investigated the role of full-strain measurements on soil sample surfaces using digital image correlation techniques and found that the observed cracking was restricted mostly to high stretching domains, either external restraint or internal flaws of the shrinking soil.

86 citations


"Effect of hydraulic gradient on swe..." refers background in this paper

  • ...The existence of discontinuities in these liners owing to the desiccation act as preferential flow paths and result in destroying their primary function as barrier layers (McBrayer et al. 1997; Albright et al. 2006; Wang et al. 2018; Julina and Thyagaraj 2019; Tang et al. 2019; Cheng et al. 2021)....

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Journal ArticleDOI
TL;DR: In this article, a flow-pump method was used to measure the permeability of sand, sandy silt and silty clay specimens in a conventional triaxial system by introducing and withdrawing water at known constant flow rates.
Abstract: Permeability measurements were conducted with the flow-pump method on sand, sandy silt and silty clay specimens in a conventional triaxial system by introducing and withdrawing water at known constant flow rates into the base of a specimen with a flow-pump, and by monitoring the head difference induced across the length of the specimen with a sensitive differential pressure transducer. The results show that the previously reported advantages of the flow-pump method, compared with conventional constant head and falling head methods, were realized for permeability measurements in conventional triaxial equipment. These advantages are that direct flow rate measurements are avoided together with the associated errors that arise from the effects of contaminants on capillary menisci and the long periods of time involved in flow rate measurements; permeability measurements can be obtained much more rapidly and at substantially smaller gradients; errors from the small intercept in the otherwise linear flow rate ve...

85 citations


"Effect of hydraulic gradient on swe..." refers background in this paper

  • ...…conductivity owing to the migration of fine soil particles and seepage-induced consolidation of soil which eventually alter the hydraulic conductivity of the soils (Olsen, Nichols, and Rice 1985; Fox 1996; Shackelford et al. 2000; Kodikara and Rahman 2002; ASTM D5856-15 2015; ASTM D5084-16a 2016)....

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Journal ArticleDOI
TL;DR: Unsaturated hydraulic conductivity is the primary soil parameter required when performing seepage analyses for unsaturated-saturated soil systems as discussed by the authors. But it is not a suitable soil parameter for seeping.
Abstract: Unsaturated hydraulic conductivity is the primary soil parameter required when performing seepage analyses for unsaturated–saturated soil systems. Unsaturated hydraulic conductivity is also one of ...

85 citations


"Effect of hydraulic gradient on swe..." refers background in this paper

  • ...…also be estimated from the field (e.g. Albrecht and Cartwright 1989; Liu et al. 2003; Albright et al. 2006) and laboratory (e.g. Wang and Benson 1995; Hoffmann, Alonso, and Romero 2007; Li, Zhang, and Fredlund 2009; Alonso, Romero, and Hoffmann 2011; Cheng et al. 2021) infiltration test results....

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Journal ArticleDOI
TL;DR: In this paper, two prototype liners were constructed at a site near Austin, Texas, using clays of low and high plasticity, and the overall hydraulic conductivity (k) of each liners was determined by ponding water on the liners and measuring the rate of seepage.
Abstract: Two prototype liners were constructed at a site near Austin, Texas, using clays of low and high plasticity. The clays were compacted to 100% of standard Proctor density at a water content slightly wet of optimum using a sheepsfoot roller. The overall hydraulic conductivity (k) of each liner was determined by ponding water on the liners and measuring the rate of seepage. The field-measured k’s of the liners were surprisingly high (4x10\u-\u6 and 9x10\u-\u6 cm/s). After water in the ponds was removed, laboratory permeability tests were performed on hand-carved samples obtained from the liners, on samples obtained with a thin-walled sampling tube, and on laboratory-compacted samples. Field permeability tests were also performed with ring infiltrometers. The tests showed that: (1) Essentially all of the laboratory tests, even on undisturbed samples, produced a measured k that was approximately 1,000 times less than the field-measured k, and (2) ring infiltration tests showed considerable scatter but the average k was close to the overall field-mesasured k. The findings raise important questions about whether laboratory permeability tests on compacted clay are relevant to clay liners and reinforce previous suggestions that compacted clay liners may contain numerous hydraulic defects such as fissures, slickensides, zones of poor bonding between clods of clay, and zones of relatively poor compaction. The desirability of field permeability tests is evident from the results reported.

83 citations


"Effect of hydraulic gradient on swe..." refers background in this paper

  • ...…to the laboratory small-scale experiments, the large-scale in-situ tests are usually preferred because defects such as macropores, fissures or desiccation cracks formed due to drying are accounted, in addition to the benefit of representation of large soil mass (Day and Daniel 1985; Daniel 1989)....

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Journal ArticleDOI
TL;DR: In this article, the state-of-the-art for conductivity testing of compacted clay soils is summarized. And the authors present a review of the state of the art for conducting hydraulic conductivity tests.
Abstract: This paper summarizes the state of the art for in situ conductivity testing of compacted clay soils. Nine methods of testing are reviewed: (1) The Boutwell permeameter; (2) constant‐head borehole permeameters, e.g., the Guelph permeameter; (3) porous probes, e.g., the BAT device; (4) open, single‐ring infiltrometers; (5) open, double‐ring infiltrometers; (6) closed, single‐ring infiltrometers, (7) sealed, double‐ring infiltrometers; (8) the air‐entry permeameter; and (9) lysimeter pans. Installation procedures are given, equations for calculating hydraulic conductivity are presented, simplifying assumptions are listed, and case histories are reviewed. Each type of permeameter has advantages. The Boutwell permeameter is especially convenient for measurement of the vertical and horizontal hydraulic conductivity. Borehole permeameters and porous probes provide data relatively quickly but permeate a relatively small volume of soil. Of the permeameters that can permeate large volume of soil, the sealed double‐...

82 citations


"Effect of hydraulic gradient on swe..." refers background or methods in this paper

  • ...In practice, the steady state infiltration rates are determined in the field using double ring infiltrometers through surface impoundment with low hydraulic gradient to simulate the actual field conditions and other methods (Daniel 1989; ASTM D3385-09 2009)....

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  • ...In comparison to the laboratory small-scale experiments, the large-scale in-situ tests are usually preferred because defects such as macropores, fissures or desiccation cracks formed due to drying are accounted, in addition to the benefit of representation of large soil mass (Day and Daniel 1985; Daniel 1989)....

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  • ...…to the laboratory small-scale experiments, the large-scale in-situ tests are usually preferred because defects such as macropores, fissures or desiccation cracks formed due to drying are accounted, in addition to the benefit of representation of large soil mass (Day and Daniel 1985; Daniel 1989)....

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