Influence of salt concentration on volume shrinkage and water retention characteristics of compacted GMZ bentonite

He, Yong; Chen, Yong-Gui; Ye, Weimin; Bao, Chen; Cui, Yu‐Jun

doi:10.1007/s12665-015-5228-3

Cited by 34 publications

(14 citation statements)

References 48 publications

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“…A possible explanation to this observation could be that the specimens with lower dry density have more pore space for pore fluid intrusion, which enhanced the increase in the interaggregate or macropores induced by the contraction of clay aggregates [59]. However, for compacted bentonite with higher dry density, less pore-fluid intrusion is likely to be insufficient to form enough DDL in a small interlayer space [37,69].…”

Section: A Modified Swrc Model Withmentioning

confidence: 99%

“…In this regard, various investigations [33][34][35][36] have been conducted. Meanwhile, experimental results also indicated that the salt concentration of infiltrating groundwater can influence the water retention properties of compacted bentonite/expansive clay specimens when used as buffer/backfill materials in the HLW repository [37][38][39]. For wetting or drying with a given concentration pore fluid, Fredlund and Xing [28] assumed that the maximum osmotic suction in less active soils is approximately 1.5 MPa.…”

Section: Introductionmentioning

confidence: 99%

“…China's deep geological disposal program for HLW began in the 1980s. Beishan of Gansu has been selected as the preferred site for construction of repository in China [23,37]. Bentonite from Gaomiaozi (GMZ), 300 km northwest of Beijing, has been reckoned as the preferred "buffer/backfill material" for building engineering barriers in deep geological repositories [37].…”

Section: Introductionmentioning

confidence: 99%

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Experimental and Modeling Study of Soil Water Retention Curves of Compacted Bentonite considering Salt Solution Effects

Zhang

2019

Geofluids

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Due to its low hydraulic conductivity, high swelling capacity, and good adsorption properties, the Gaomiaozi (GMZ) bentonite has been selected as potential buffer/backfill materials for construction of engineered barriers in the deep geological repository for disposal of high-level nuclear waste (HLW) in China. Investigation of salt solution effects on the water retention properties of compacted bentonite is of great importance in the context of geological disposal of HLW based on the multibarrier concept. In this study, amended specimens were obtained through a spray of different concentrations of salt solutions to reach target salt contents, respectively. With employment of the vapor phase technique for suction control, water retention tests were conducted on densely compacted GMZ bentonite (1.7 Mg/m3) with different salt contents under confined conditions. Corresponding soil water retention curves (SWRCs) were obtained. Analysis indicates that, for a given suction, the measured water content of GMZ bentonite specimen increases as the salt content (or pore fluid concentration) increases. The influencing rate depends on suction. For lower suctions (lower than 38 MPa), the water retention capacity increases as the salt content increases, while for higher suctions (higher than 38 MPa), the influence can be negligible. Based on the Fredlund and Xing (1994) equation, a soil water retention model was proposed for simulation of the SWRCs of compacted GMZ bentonite with consideration of pore fluid chemistry. Parameters were analyzed and determined with consideration of influences of the pore fluid concentration. Verification indicates that the SWRCs simulated by the proposed model are well agreed with the measured ones.

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Section: A Modified Swrc Model Withmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental and Modeling Study of Soil Water Retention Curves of Compacted Bentonite considering Salt Solution Effects

Zhang

2019

Geofluids

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“…Gajo and Maines (2007) investigated the mechanical behavior of active clays affected by pore fluid acidity and alkalinity [12]. Recently, many researchers have focused on the influence of infiltrating solutions coupled with rock fracture on the water retention curves, swelling behavior, hydraulic conductivity, and yield stresses of highly compacted bentonite [13,14,15,16,17]. Most previous studies have been conducted with reference to pure unsaturated bentonite or active clays prepared by different procedures, but the chemical effect on saturated remolded clay has rarely been mentioned.…”

Section: Introductionmentioning

confidence: 99%

Explanation of the Influence of Sodium Chloride Solution on Volume Deformation and Permeability of Normally Consolidated Clays

Zhang

Wang

2019

Materials

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The marine clays located in the Southeast area of China are characterized by their higher water content, higher compressibility and higher salinities. This soil is mainly composed of illite/montmorillonite interlayer minerals. Previous research has shown that the saline water significantly influences the liquid limit and other physical characteristics of the clays. As the desalination of pore water occurs as a result of freshwater or rainfalls, the physical and mechanical behaviors of the soft marine clays changes, and this can lead to potential hazards for infrastructure. Therefore, it is essential to understand the effects of chemistry variations and to predict the long-term foundation deformations. Based on previous works, the deformation behavior of artificial soils corresponding to a mixture of kaolinite and bentonite (the mass ratios of bentonite were 0%, 5%, 10% and 20%) was further discussed in a ln(1 + e)-logp’ system. The permeabilities of the samples mixed with different concentrations of sodium chloride solutions were compared based on oedometer tests. The micro-structures in the samples were investigated by SEM (scanning electronic microscopy) tests. The declining trend of a newly defined volume compression index Ccv and swelling index Csv with pore water salinity and e0/eL was observed when the initial void ratios e0 of the samples were close. The permeability coefficient k and the slopes Ck = e/logk of the mixtures increased with the ionic concentrations. Finally, the changes in volume deformations and permeabilities induced by sodium chloride solution are discussed based on ‘suction pressure’ and initial void compression at micro-level. This paper proves that the influences of salinity on the mechanical behavior of clays are mainly attributable to the interaction between diffused double layers, and these findings are helpful for improving the constitutive model of soft clays when taking pore water chemistry changes into consideration.

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“…In particular, the influence of clay fabric and its evolution have been discussed in the literature highlighting the role of compaction water content (Thom et al 2007), the hydro-mechanical path (Lloret et al 2003;Romero et al 2011;Dieudonne et al 2014a;Seiphoori et al 2014;Della Vecchia et al 2015) and the chemical 35 composition of the pore fluid (Mata et al 2002;He et al 2016;Thyagaraj and Salini 2016). Accordingly, in recent years, water retention models have been developed to account for the role of the compacted clay fabric.…”

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confidence: 99%

Water retention model for compacted bentonites

2017

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Influence of salt concentration on volume shrinkage and water retention characteristics of compacted GMZ bentonite

Cited by 34 publications

References 48 publications

Experimental and Modeling Study of Soil Water Retention Curves of Compacted Bentonite considering Salt Solution Effects

Experimental and Modeling Study of Soil Water Retention Curves of Compacted Bentonite considering Salt Solution Effects

Explanation of the Influence of Sodium Chloride Solution on Volume Deformation and Permeability of Normally Consolidated Clays

Water retention model for compacted bentonites

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