scholarly journals Experimental study on the influence of preliminary desiccation on the swelling pressure and hydraulic conductivity of compacted bentonite

Clay Minerals ◽  
2018 ◽  
Vol 53 (4) ◽  
pp. 733-744 ◽  
Author(s):  
Lin Zhi Lang ◽  
Wiebke Baille ◽  
Snehasis Tripathy ◽  
Tom Schanz
Keyword(s):  
Hydraulic Conductivity ◽  
Swelling Pressure ◽  
Shrinkage Strain ◽  
Volumetric Shrinkage ◽  
Barrier Materials ◽  
Compacted Bentonite ◽  
Swelling Capacity ◽  
Pressure Tests ◽  
Volumetric Shrinkage Strain ◽  
Volume Swelling

ABSTRACTIn deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing thermo-hydro-mechanical boundary conditions in the repositories may affect the swelling capacity and permeability of the compacted bentonites. In this study, the effect of preliminary desiccation on the subsequent hydro-mechanical behaviour (swelling pressure and hydraulic conductivity) of compacted Calcigel bentonite was investigated experimentally at 22°C and 80°C. In the first stage of the test, the compacted specimens were subjected to suction-controlled desiccation at 22°C and 80°C using the vapour-equilibrium technique. After the water content reached equilibrium at a given suction, the axial, radial and volumetric shrinkage strains were measured. Afterwards, constant-volume swelling-pressure tests were performed on the desiccated specimens (second test stage) by saturating the dried specimens with deionized water at 22°C and 80°C. At the end of the swelling-pressure test, the hydraulic conductivities of four saturated specimens were measured at each temperature. The volumetric shrinkage strain of the compacted bentonite during desiccation is controlled by suction instead of temperature. In addition, the preliminary desiccation increases both the swelling pressure and hydraulic conductivity of compacted bentonite, particularly if compacted bentonite undergoes extreme desiccation at an applied suction of >700 MPa.

Modeling Hydraulic Conductivity and Swelling Pressure of Several Kinds of Bentonites Affected by Salinity of Water

2010 ◽  
Author(s):  
Yukihisa Tanaka ◽  
Takuma Hasegawa ◽  
Kunihiko Nakamura
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Ground Water ◽  
Quantitative Evaluation ◽  
Coastal Area ◽  
Evaluation Method ◽  
Saline Water ◽  
Swelling Pressure ◽  
Compacted Bentonite ◽  
Swelling Characteristics

In case of construction of repository for radioactive waste near the coastal area, the effect of salinity of water on hydraulic conductivity as well as swelling pressure of bentonite as an engineered barrier should be considered because it is known that the hydraulic conductivity of bentonite increases and swelling pressure decreases with increasing salinity of water. Though the effect of salinity of water on hydraulic conductivity and swelling pressure of bentonite has been investigated experimentally, it is necessary to elucidate and to model the mechanism of the phenomenon because various kinds of bentonites may possibly be placed in various salinities of ground water. Thus, in this study, a model for evaluating hydraulic conductivity as well as swelling pressure of compacted bentonite is proposed considering the effect of salinity of water as follows: a) Change in number of flakes of a stack of montmorillonite because of cohesion. b) Change in viscosity of water in interlayer between flakes of montmorillonite. Quantitative evaluation method for hydraulic conductivity and swelling characteristics of several kinds of bentonites under saline water is proposed based on the model mentioned above.

scholarly journals Investigating the contribution of claystone to the swelling pressure of its mixture with bentonite

2020 ◽  
Vol 195 ◽  
pp. 03043
Author(s):  
Zhixiong Zeng ◽  
Yu-Jun Cui ◽  
Nathalie Conil ◽  
Jean Talandier
Keyword(s):  
Radioactive Waste ◽  
Safety Assessment ◽  
Swelling Pressure ◽  
Radioactive Waste Disposal ◽  
Inert Material ◽  
Dry Density ◽  
Test Results ◽  
Pressure Tests ◽  
Volume Swelling

Compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been considered as a possible sealing/backfilling material in the French deep geological radioactive waste disposal. The swelling pressure of such mixture is an important factor in the design and long-term safety assessment of deep geological repositories. In this study, constant-volume swelling pressure tests were performed on the mixtures with different claystone fractions and dry densities. The test results show that the swelling pressure of the mixtures decreased with the increasing claystone fraction and decreasing dry density. According to the experimental results, the contribution of claystone to the global swelling pressure was further investigated. It was found that the deformation of claystone and its contribution to swelling pressure was highly dependent on the claystone fraction. As the claystone fraction was larger than 30%, the claystone in the mixture swelled, contributing to the global swelling pressure; On the contrary, as the claystone fraction was less than 30%, the swelling of claystone was inhibited by the bentonite and it worked an inert material without any contribution to the swelling pressure.

scholarly journals Swelling pressure of a sodium bentonite in solutions of different suction

2021 ◽  
Vol 337 ◽  
pp. 01007
Author(s):  
Shin Sato ◽  
Shuichi Yamamoto ◽  
Tomoyoshi Nishimura
Keyword(s):  
Swelling Pressure ◽  
Adsorbed Water ◽  
Dry Density ◽  
Test Program ◽  
Sand Mixture ◽  
Compacted Bentonite ◽  
Volume Swelling ◽  
Wetting Process ◽  
Unsaturated Condition ◽  
Water Amount

In this study, the swelling pressure of unsaturated, compacted bentonite-sand mixture was measured, which the all samples had experiment in dying-wetting history in suction changing. This test program used Kunigel V1 as sodium type. Constant volume swelling test was conducted out that swelling pressure was measured using a developed apparatus. A pressure sensor was mounted in the swelling test apparatus. Previously, the all samples deformed due to suction change (i.e. drying-wetting process in suction). Two types were prepared before applying suction that were initial unsaturated condition and saturated condition on same initial dry density. Swelling pressure and adsorbed water amount was monitored in the test, which lasted for one month.

scholarly journals Desiccation-Induced Volumetric Shrinkage of Compacted Metakaolin-Treated Black Cotton Soil for a Hydraulic Barriers System

2016 ◽  
Vol 24 (1) ◽  
pp. 1-5 ◽  
Author(s):  
George Moses ◽  
Oriola F. O. Peter ◽  
Kolawole J. Osinubi
Keyword(s):  
Shrinkage Strain ◽  
West African ◽  
Degree Of Saturation ◽  
Volumetric Shrinkage ◽  
Black Cotton Soil ◽  
Waste Containment ◽  
Intermediate Energies ◽  
Volumetric Shrinkage Strain ◽  
Water Contents ◽  
Hydraulic Barriers

AbstractBlack cotton soil treated with up to 24% metakaolin (MCL) content was prepared by molding water contents of −2, 0, 2, 4 and 6% of optimum moisture content (OMC) and compacted with British Standard Light (BSL) and West African Standard (WAS) or ‘Intermediate’ energies. The specimens were extruded from the compaction molds and allowed to air dry in a laboratory in order to assess the effect of desiccation-induced shrinkage on the compacted mix for use as a hydraulic barrier in a waste containment application. The results recorded show that the volumetric shrinkage strain (VSS) values were large within the first 10 days of drying; the VSS values increased with a higher molding of the water content, relative to the OMC. The VSS generally increased with a higher initial degree of saturation for the two compactive efforts, irrespective of the level of MCL treatment. Generally, the VSS decreased with an increasing MCL content. Only specimens treated with a minimum 20% MCL content and compacted with the WAS energy satisfied the regulatory maximum VSS of 4% for use as a hydraulic barrier.

Fundamental Properties of Monolithic Bentonite Buffer Material Formed by Cold Isostatic Pressing for High-Level Radioactive Waste Repository

1999 ◽  
Vol 556 ◽  
Author(s):  
S. Kawakami ◽  
Y Yamanaka ◽  
K. Kato ◽  
H. Asano ◽  
H. Ueda
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Swelling Pressure ◽  
Cold Isostatic Pressing ◽  
Small Samples ◽  
Isostatic Pressing ◽  
High Level Radioactive Waste ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
High Level

AbstractThe methods of fabrication, handling, and emplacement of engineered barriers used in a deep geological repository for high level radioactive waste should be planned as simply as possible from the engineering and economic viewpoints. Therefore, a new concept of a monolithic buffer material around a waste package have been proposed instead of the conventional concept with the use of small blocks, which would decrease the cost for buffer material. The monolithic buffer material is composed of two parts of highly compacted bentonite, a cup type body and a cover. As the forming method of the monolithic buffer material, compaction by the cold isostatic pressing process (CIP) has been employed.In this study, monolithic bentonite bodies with the diameter of about 333 mm and the height of about 455 mm (corresponding to the approx. 1/5 scale for the Japanese reference concept) were made by the CIP of bentonite powder. The dry densities: pd of the bodies as a whole were measured and the small samples were cut from several locations to investigate the density distribution. The swelling pressure and hydraulic conductivity as function of the monolithic body density for CIP-formed specimens were also measured.High density ( ρd: 1.4–2.0 Mg/m3) and homogeneous monolithic bodies were formed by the CIP. The measured results of the swelling pressure (3–15 MPa) and hydraulic conductivity (0.5–1.4×10−3 m/s) of the specimens were almost the same as those for the uniaxial compacted bentonite in the literature. It is shown that the vacuum hoist system is an applicable the handling method for emplacement of the monolithic bentonite.

Desiccation Induced Shrinkage of Compacted Lateritic Soil Treated via Enzymatic Induced Calcium Carbonate Precipitation Technique

2021 ◽  
Vol 1030 ◽  
pp. 110-123
Author(s):  
Muttaqa Uba Zango ◽  
Khairul Anuar Kassim ◽  
Abubakar Sadiq Muhammed ◽  
Kamarudin Ahmad ◽  
Jodin Makinda
Keyword(s):  
Calcium Carbonate ◽  
Shrinkage Strain ◽  
Engineering Properties ◽  
Volumetric Shrinkage ◽  
Natural Soil ◽  
Residual Soil ◽  
Carbonate Precipitation ◽  
Calcium Carbonate Precipitation ◽  
British Standard ◽  
Volumetric Shrinkage Strain

Exploring the biological process to enhance the engineering properties of soil have received enormous recognition in recent years. Enzymatic induced calcium carbonate precipitation (EICP) is one of the bio-inspired methods of utilizing free urease to precipitates calcite from urea and calcium ions for bettering the geotechnical properties of poor soils. In this research, the EICP technique was used to improve the volumetric shrinkage strain of compacted soil liner. In this work, the residual soil was treated with various concentrations of cementations ranging from 0.25 to 1.0 M, and the soil was subjected to Atterberg limit tests, compaction test using British standard light (BSL) and reduced British standard light (RBSL) and desiccation drying volumetric shrinkage strain test. The study's findings revealed a remarkable improvement in the liquid limit and plasticity index of the treated residual soils compared to natural soil. It was also found that the volumetric shrinkage strain of the treated soil reduces progressively from 5.24% of natural to 1.49% at 1.0 M cementation solution when the soils were prepared at 0% OMC and BSL compaction effort. Based on the consideration of permissible VSS of less than 4%, the best treatment was obtained at 1.0 M for both BSL and RBSL prepared samples. Similarly, the best compaction plane is found in the treated with 1.0 M cementation solution.

Improvement of Barrier Soil Properties with Fly Ash to Minimize Desiccation Shrinkage

2012 ◽  
Vol 7 ◽  
pp. 1-11 ◽  
Author(s):  
Agapitus A. Amadi
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Water Content ◽  
Dry Weight ◽  
Shrinkage Strain ◽  
Volumetric Shrinkage ◽  
Unit Weight ◽  
British Standard ◽  
Fine Grained ◽  
Dry Unit Weight

Barrier Systems Built with Fine Grained Soils Frequently Loose their Hydraulic Integrity due to Desiccation Cracking either during Construction or Shortly Thereafter. Moreover, Typical Specifications for the Construction of Compacted Soil Liners and Covers Require that the Soil Be Compacted Wet of Optimum Water Contents to Achieve the Lowest Possible Hydraulic Conductivity, a Condition that Results in High Desiccation Shrinkage Values. however, such Soils Can Be Treated with Fly Ash to Maintain Low and Tolerable Desiccation Shrinkage Strains. in this Study, Volumetric Shrinkage Strains of Representative Fine Grained Soil Containing 0 – 20% Fly Ash by Dry Weight of Soil Compacted with the British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy, (BSH) Compaction Efforts at Moisture Contents Ranging from 10 – 20% Were Evaluated. Measurements Indicate that Volumetric Shrinkage Strain Decreased with Higher Fly Ash Content and that Fly Ash Effectively Reduced the Shrinkage of Untreated Soil Prepared Wet of Optimum from 4.4 – 7.7% to Values Well below the 4% Threshold. the Measured Shrinkage Strains Were Related to Water Content and Dry Unit Weight on the Dry Unit Weight – Moulding Water Content Curve in what Is Referred to as Acceptable Zone. Data Points within the Acceptable Zone Represent Test Results with Shrinkage Strain ≤ 4% which Ensures Compaction Efficiency. this Study Therefore Established that Fly Ash Application and Appropriate Regulation of the Moulding Water Content Are Feasible Means of Reducing the Risk of Barrier Soil Damage by Shrinkage Cracks while still Realizing Very Low Hydraulic Conductivity and Adequate Strength.

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