INTERPRETATIONS OF COMPRESSION/SWELLING BEHAVIOR OF COMPACTED BENTONITE USING CONSTANT WATER-CONTENT LINE AND CONSTANT DEGREE-OF-SATURATION LINE

Compacted bentonite materials are often considered as a buffer material in the geological radioactive waste disposal. This bentonite is expected to fill up the space between the waste and the surrounding ground by swelling. Therefore, understanding the surrounding ground, i.e., groundwater behavior in bentonite, as a buffer material, is essential in order to evaluate the bentonite buffer performance and guarantee long-term safety. The monitoring system of the water saturation level in compacted bentonite is required because water content in buffer material may influence its elastic properties. In this study, the correlation between water content and elasticity in unsaturated compressed bentonite was experimentally evaluated. The evaluation was done by measuring the sound velocity of both longitudinal wave and transverse wave. As a result, it can be confirmed that ultrasonic velocities could evaluate a degree of saturation and bulk modulus of compacted bentonite.

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Gas permeability of a compacted bentonite–sand mixture: coupled effects of water content, dry density, and confining pressure

Canadian Geotechnical Journal ◽

10.1139/cgj-2014-0371 ◽

2015 ◽

Vol 52 (8) ◽

pp. 1159-1167 ◽

Cited By ~ 26

Author(s):

Jiang-Feng Liu ◽

Frédéric Skoczylas ◽

Jean Talandier

Keyword(s):

Water Content ◽

Gas Permeability ◽

Confining Pressure ◽

Degree Of Saturation ◽

Dry Density ◽

Sand Mixture ◽

Compacted Bentonite ◽

High Confining Pressure ◽

Confining Pressures ◽

Gas Tightness

The gas-tightness of compacted bentonite–sand mixtures is important to the total sealing efficiency of geological repositories. The initial aim of this work was to determine whether the combination of a high confining pressure (Pc) and incomplete saturation could cause a bentonite–sand mixture to become gas-tight. The results show that the physical characteristics of the materials (degree of saturation, Sr; porosity, [Formula: see text]; and dry density, ρd) are very sensitive to changes in the applied confining pressures and their own swelling deformation (or shrinkage). The combination of these changes affects the sample’s effective gas permeability (Keff). For materials prepared at a relative humidity (RH) of 98%, Keff decreased from 10−16 to 10−20 m2 when Pc increased from 1 to 7 MPa. This means that gas-tightness can be obtained for a compacted bentonite–sand mixture when the materials experience a series of changes (e.g., w, Sr, [Formula: see text], and ρd). In addition, larger irreversible deformation (or hysteresis) was observed during the loading–unloading cycle for the sample with higher water content. This phenomenon may be attributed to larger interactions between the macrostructural and microstructural deformations and the decrease of preconsolidation pressure during hydration.

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Longitudinal and Shear Wave Velocities Measurement in Compacted Bentonite for Water Content

E3S Web of Conferences ◽

10.1051/e3sconf/20184301016 ◽

2018 ◽

Vol 43 ◽

pp. 01016

Author(s):

Shun Kimura ◽

Kazumi Kitayama ◽

Hideharu Takahashi ◽

Kazushi Kimoto ◽

Katsuyuki Kawamura ◽

...

Keyword(s):

Bulk Modulus ◽

Water Content ◽

Degree Of Saturation ◽

Ultrasonic Velocities ◽

Compacted Bentonite ◽

Wave Velocities ◽

Shear Wave Velocities ◽

Bentonite Buffer ◽

Buffer Material

Bentonite is a good candidate of buffer material for disposal repository of high-level radioactive waste. Understanding groundwater behavior in bentonite buffer material is important in order to evaluate the bentonite buffer performance and guarantee long-term safety. Elastic constants of the bentonite buffer material are important parameters for the long-term safety. Water content in buffer material may have an influence on its elastic properties. For this reason, the monitoring system of the water saturation level in compacted bentonite is required. In this study, the ultrasonic velocity measurement method for evaluation of water content in compacted bentonite was proposed. At first, the effect of a degree of saturation in compacted bentonite on the longitudinal and shear wave velocities was investigated experimentally. In addition, the elastic property, bulk modulus, in unsaturated compacted bentonite were evaluated by ultrasonic velocities. As a result, it can be confirmed that ultrasonic velocities can evaluate a degree of saturation and bulk modulus of compacted bentonite.

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Using time domain reflectometry in triaxial testing

Canadian Geotechnical Journal ◽

10.1139/t00-060 ◽

2000 ◽

Vol 37 (6) ◽

pp. 1325-1331

Author(s):

J LH Grozic ◽

M E Lefebvre ◽

P K Robertson ◽

N R Morgenstern

Keyword(s):

Cyclic Loading ◽

Water Content ◽

Time Domain ◽

Void Ratio ◽

Time Domain Reflectometry ◽

Volumetric Water Content ◽

Degree Of Saturation ◽

Triaxial Testing ◽

Empirical Correlations ◽

Static And Cyclic Loading

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree of saturation and volumetric water content during triaxial testing could be determined. The TDR was then put to use in a laboratory program designed to investigate the response of loose gassy sand under static and cyclic loading. Because of the TDR measurements it was possible to determine the degree of saturation and void ratio of the gassy specimens. The TDR miniprobe proved to be accurate, simple to use, and inexpensive to build.Key words: time domain reflectometry, TDR, triaxial testing, gassy, unsaturated.

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Physical properties, electrical resistivity, and strength characteristics of carbonated silty soil admixed with reactive magnesia

Canadian Geotechnical Journal ◽

10.1139/cgj-2015-0053 ◽

2015 ◽

Vol 52 (11) ◽

pp. 1699-1713 ◽

Cited By ~ 36

Author(s):

G.H. Cai ◽

Y.J. Du ◽

S.Y. Liu ◽

D.N. Singh

Keyword(s):

Compressive Strength ◽

Electrical Resistivity ◽

Water Content ◽

Unconfined Compressive Strength ◽

Ground Improvement ◽

Strength Characteristics ◽

Degree Of Saturation ◽

Initial Water Content ◽

Silty Soil ◽

Reactive Magnesia

Soil electrical resistivity has been used quite extensively for assessing mechanical properties of chemically treated soils in the recent past. One of the most innovative applications of this technique could be in the field of ground improvement wherein carbonated reactive magnesia (MgO) is employed for treating soils. With this in view, a systematic study that targets the application of electrical resistivity to correlate physical and strength characteristics of the carbonated reactive MgO-admixed silty soil is initiated, and its details are presented in this manuscript. To achieve this, reactive MgO-admixed soils were carbonized by exposing them to CO2 for different durations, and subsequently their electrical resistivity and unconfined compressive strength were measured. In this context, the role of a parameter, the ratio of the initial water content of the virgin soil to reactive MgO content (designated as w0/c), has been highlighted. It has also been demonstrated that w0/c is able to correlate, uniquely and precisely, with the physicochemical parameters of the soils (viz., unit weight, water content at failure, porosity, degree of saturation, and soil pH), electrical resistivity, and unconfined compressive strength at various carbonation times. In addition, microstructural properties have been obtained from the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry analyses. These properties have been used to substantiate the findings related to the carbonation of the reactive MgO-admixed soils.

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Investigation into water retention behaviour of deformable soils

Canadian Geotechnical Journal ◽

10.1139/cgj-2011-0409 ◽

2013 ◽

Vol 50 (2) ◽

pp. 200-208 ◽

Cited By ~ 65

Author(s):

Simon Salager ◽

Mathieu Nuth ◽

Alessio Ferrari ◽

Lyesse Laloui

Keyword(s):

Water Content ◽

Soil Water ◽

Water Retention ◽

Void Ratio ◽

Degree Of Saturation ◽

Retention Data ◽

Soil Water Retention ◽

Retention Behaviour ◽

Wide Range ◽

Water Retention Behaviour

The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying–wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.

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Swelling of Layered Potassium Ruthenate into Nanosheet Crystallites

MRS Proceedings ◽

10.1557/proc-1148-pp03-36 ◽

2008 ◽

Vol 1148 ◽

Author(s):

Katsutoshi Fukuda ◽

Hisato Kato ◽

Wataru Sugimoto ◽

Yoshio Takasu

Keyword(s):

Water Content ◽

Colloidal Suspension ◽

Intercalation Compound ◽

Swelling Behavior ◽

Layered Compound ◽

Interlayer Water ◽

Tetrabutylammonium Hydroxide

AbstractThe swelling and exfoliation behaviors of layered potassium ruthenate and the resultant unilamellar crystallites of RuO2.10.2− with nanosheet morphology were studied. The reaction of layered H0.2RuO2.1·0.9H2O with tetrabutylammonium hydroxide (TBA+OH−) was found to be extremely sensitive to the interlayer water content. The use of highly hydrous layered protonic ruthenate was essential for obtaining direct exfoliation. The swelling behavior was also affected by the ratio of TBA+ to ion-exchangeable H+ in the layered compound. At low ratios of TBA+/H+≤1, the layered precursor scarcely exfoliated and mostly deposited as an intercalation compound. In the intermediate TBA+/H+ range, an auburn colloidal suspension containing exfoliated nanosheets was formed, while much larger ratios were less favorable for the exfoliation.

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Variation of Initial Soil Suction with Compaction Conditions for Clayey Soils

Journal of Mechanics ◽

10.1017/jmech.2012.52 ◽

2012 ◽

Vol 28 (3) ◽

pp. 431-437 ◽

Cited By ~ 4

Author(s):

S.-R. Yang ◽

H.-D. Lin ◽

W.-H. Huang

Keyword(s):

Water Content ◽

Clay Fraction ◽

Degree Of Saturation ◽

Soil Suction ◽

Clayey Soils ◽

Test Results ◽

Wide Range ◽

Initial Soil ◽

Compaction Energy ◽

The Relationship

AbstractIn this study, the initial soil suction of as-compacted clayey soils was evaluated for various compaction conditions, covering a wide range of compaction energy and molding water content. The soil specimens were prepared by impact compaction under three levels of compaction energy. The filter paper method was used to measure the initial soil suction of as-compacted specimens. Test results indicate that the relationship between the soil suction and the molding water content is bilinear under three different compaction energies. However, the effect of compaction energy on soil suction is different for the soils with different amounts of clay fraction and is elucidated by the macro soil properties. The change of soil suction due to different compaction energies can be predicted by the void ratio and the degree of saturation.

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Nomograms for calculating the void ratio ε, porosity n, degree of saturation G with respect to unit weight γr, bulk specific weight of skeleton γsk, and water content of soil W

Soil Mechanics and Foundation Engineering ◽

10.1007/bf01706108 ◽

1965 ◽

Vol 2 (4) ◽

pp. 246-247

Author(s):

A. I. Danilov

Keyword(s):

Water Content ◽

Void Ratio ◽

Specific Weight ◽

Degree Of Saturation ◽

Unit Weight

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Effect of soil moisture content on the bearing capacity of small bored piles in the unsaturated soil of Maringá, Paraná, Brazil

MATEC Web of Conferences ◽

10.1051/matecconf/202133703006 ◽

2021 ◽

Vol 337 ◽

pp. 03006

Author(s):

Verônica Ricken Marques ◽

Antonio Belincanta ◽

Mary-Antonette Beroya-Eitner ◽

Jorge Luis Almada Augusto ◽

Ewerton Guelssi ◽

...

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Bearing Capacity ◽

Water Content ◽

Unsaturated Soil ◽

Soil Layer ◽

Matric Suction ◽

Load Test ◽

Degree Of Saturation ◽

Static Load Test

In this study, the influence of soil moisture on the bearing capacity of piles founded in an unsaturated clay soil was investigated. The soil studied, composing the upper soil layer in Maringá, Brazil, is lateritic, has degree of saturation between 37% and 70% and has collapsible behaviour when wet. The bearing capacity was determined by full-scale load tests following the Brazilian Standard for Static Load Test. Two pile lengths, 4 m and 8 m, were considered. To analyse the influence of soil moisture, two tests were performed for each pile length: one in soil in its natural moisture content and another in pre-moistened soil. Results show that for both pile lengths, an increase in water content caused a significant reduction in bearing capacity, which is attributed to the decrease in the matric suction of the soil. This is confirmed by the results of the initial evaluation made on the variation of matric suction and its contribution to the bearing capacity with changes in water content. In summary, this study confirms that the pile bearing capacity in unsaturated soil is dependent on soil water content, highlighting the fact that the approach of assuming full saturation condition in the evaluation of the pile bearing capacity in such soil may give erroneous results. Moreover, this study demonstrate that the empirical methods most commonly used in Brazil for pile bearing capacity determination, the Décourt & Quaresma and Aoki & Velloso methods, are overly conservative when applied to the Maringá soil.

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