Variation of Suction during Wetting of Unsaturated Collapsible Gypseous Soils

Al-Obaidi, Ahmed; Fattah, Mohammed Y.; Al-Dorry, Mohammed Kh.

doi:10.14419/ijet.v7i4.37.23621

Cited by 18 publications

(5 citation statements)

References 6 publications

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“…In our tests on the loess strata, the wall of drillhole is prone to collapse during WCD, whereas the collapse of hole rarely occurs during DD and WD drillings. This is because that loess has strong collapsibility and the use of a large amount of water during WCD leads to destruction of loess structure (Al-Obaidi et al, 2018;Fattah et al, 2019). In terms of drilling efficiency, DD, WD, and WCD took averagely 0.6, 0.4, and 0.35 h to proceed 1 m, respectively, and the drilling velocity with WD or WCD is 30% higher than that with DD.…”

Section: Application Evaluationmentioning

confidence: 99%

Influence of Drilling Methods on the Results of Standard Penetration Test in Loess–Paleosol Sequence

et al. 2022

Front. Built Environ.

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Standard penetration test (SPT) is an important in situ measurement for field investigation of geotechnical and geological engineering. The drilling approaches for implementation of SPT can be classified into dry, wet, and water circulation drillings according to the amount of water used during drilling process. However, the influences of these drilling methods on the SPT results remain unclear, especially when being used in loess–paleosol sequence that is water sensitive. In this study, SPT tests were conducted in a typical loess stratum in the Loess Plateau of China. The difference of SPT N values under the above three drilling methods was compared together with the analysis of characteristics of samples from SPT sampler. The results showed that the N value exhibits positive correlation with dry density of the soil and negative correlation with moisture content. In shallow soil, the average N value under water circulation drilling was slightly higher than that of dry and wet drilling. This is because that the residual soil at the bottom of the drillhole caused by water circulation drilling provides additional penetration resistance. In deep soil, the difference of average N values among all three drilling methods was minimal although the structure of the samples from the SPT sampler differs from one another, indicating the determination of soil density on the SPT result. Empirical equations were proposed for the estimation of unconfined compressive strength of loess–paleosol sequence on the basis of SPT N values under the three drilling methods. Considering the efficiency of drilling and stability of SPT results, it is suggested that wet drilling is the most applicable method for implementation of SPT in the field investigation of loess–paleosol sequence.

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Section: Application Evaluationmentioning

confidence: 99%

Influence of Drilling Methods on the Results of Standard Penetration Test in Loess–Paleosol Sequence

et al. 2022

Front. Built Environ.

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“…Mark lines are drawn to give the required thickness of the layers. Several researchers, including [10], [11], [12], [13], use the same testing box in their investigations on bearing capacity on model of footing [14]. Fig.…”

Section: Apparatus and Procedures 211 Test Boxmentioning

confidence: 99%

Behavior of Square Footing Erected on Gypseous Soil Treated by Ceramic Wastes

Ahmed

Zedan

2022

Tikrit j. eng. sci.

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Gypseous soil, as is well known, includes a specific quantity of gypsum. Gypsum is a water-soluble salt with a solubility of (2.2-2.6) gram/liter in distilled - water. As a result, the presence of gypsum poses a challenge when building structures on this soil, since gypsum dissolves when exposed to water, producing gaps between soil particles and so causing soil collapse. This study examines the behavior of a shallow foundation rested on gypseous soil. Three types of gypseous soil with gypsum contents of (61%, 45.3%, and 27.9%, respectively) are used, and treated with ceramic wastes, which is a waste product of construction. The Soil samples were collected from the site of Tikrit University's campus. The study consists of six test cases, two for each type of soil, one dry and the other wet, where the first test for each case was used as a baseline for comparison, which was the soil test without the addition of ceramic wastes, and the rest was added in three proportions (3%, 6%, and 9%) and three mixing depths for each ratio (B/2, B, 3B/2).The percentage 9% ceramic wastes gives best results of improving, the bearing capacity of the soil improved by 233%, 256 %, and 289% for high gypseous soil, and by 78%, 94%, and 111% for medium gypseous soil, with a percentage of 60%, 87%, and 113% for low gypseous soils. Adding ceramic wastes to wet gypseous soil improves the bearing strength of the soil, lowers settlement to some extent, and reduces the influence of water on it.

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“…The trend of the results is in agreement with the results of Fredlund (1995), who found that the shear strength increases with matric suction by used closed-form solution, this explains the decrease in cohesion at 14 per cent water content due to low matric suction. Al-Obaidi et al (2018) found that the drop in the readings of suction maybe because of the effect of gypsum content on the adsorption of water that leads to the saturation of the sensors surrounding area. For all soil models, the time needed to reach the zero suction (saturation state) increased with an increase of the initial dry density because of the decrease in permeability and void ratio.…”

Section: Variation Of Suction With Timementioning

confidence: 99%

Time-dependent collapse potential of unsaturated collapsible gypseous soils

Fattah

Dawood

2020

WJE

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Purpose This study aims to predict the volume changes and collapse potential (CP) associated with the changes in soil suction by using the pressure cell and the effect of initial load on soil suction. Three types of gypseous soils have been experimented in this study, sandy gypseous soil from different parts of Iraq. A series of collapse tests were carried out using the oedometer device [single oedometer test (SOT) and double oedometer test (DOT)]. In addition, large-scale model with soil dimensions 700 × 700 × 600 mm was used to show the effect of water content changes in different relations (collapse with time, stress with time, suction with time, etc.). Design/methodology/approach A series of collapse tests were carried out using the oedometer device (SOT and DOT). In addition, a large-scale model with soil dimensions 700 × 700 × 600 mm was used to show the effect of water content changes in different relations (collapse with time, stress with time, suction with time, etc.). Findings The CP increases with the increasing of the void ratio for each soil. For each soil, the CP decreased when the initial degree of saturation increased. Kerbala soil with gypsum content (30%) revealed collapse value higher than Tikrit soil with gypsum content (55%) under the same initial conditions of water content and density, this is because the higher the Cu value of Kerbala soil is, the more well-graded the soil will be. Upon wetting, the smaller particles or fractions of the well-graded soil tend to fill in the existing voids, resulting in a lower void ratio as compared to the poorly graded one. Consequently, soils with high Cu value tend to collapse more than poorly graded ones. The compressibility of the soil is low when loaded under unsaturated condition, the CP for samples tested in the DOTs under stress level 800 kPa are greater than those obtained from collapse test at a stress level of 200 kPa. Originality/value The initial value of suction for all soils increases with initial water content decreases.

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Variation of Suction during Wetting of Unsaturated Collapsible Gypseous Soils

Cited by 18 publications

References 6 publications

Influence of Drilling Methods on the Results of Standard Penetration Test in Loess–Paleosol Sequence

Influence of Drilling Methods on the Results of Standard Penetration Test in Loess–Paleosol Sequence

Behavior of Square Footing Erected on Gypseous Soil Treated by Ceramic Wastes

Time-dependent collapse potential of unsaturated collapsible gypseous soils

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