Pore size distribution and swelling behavior of compacted bentonite/claystone and bentonite/sand mixtures

Souza, R.F.C.; Pejon, Osni José

doi:10.1016/j.enggeo.2020.105738

Cited by 11 publications

(6 citation statements)

References 27 publications

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“…Referring to the standard for geotechnical testing method (GB/T 50123-2019) [38], a fixed proportion of Na-montmorillonite, kaolinite and quartz sand was firstly weighed and dried in an oven at 110°C (0% RH) for 8 h. Based on the mineral content of expansive soils in the previous studies, the mass proportion of quartz sand can be set at 60% [7,39,40]. After mixing the three materials evenly, deionized water to 10% water content was added.…”

Section: Specimen Preparationmentioning

confidence: 99%

“…Swelling and shrinking upon water content changes are the most iconic properties of expansive soils, prone to causing many engineering disasters such as cracking of buildings, destabilization of slopes, deformation of highway/railroad foundations and sliding of mine caverns [1]. In recent years, issues related to the behavior of expansive soils have received considerable attention [2][3][4], especially for the bentonite-sand mixtures that are mainly composed of Na-montmorillonite, kaolinite and quartz [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…Fig 7. The macroscopic swelling-shrinkage curve of the mixtures with a mass ratio of 1:1:3 along a wetting-drying cycle: A the swelling-shrinkage strain over time; B the vertical height of the specimen over time…”

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confidence: 99%

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Experimental study on the microscopic swelling-shrinking mechanisms of clay-sand mixtures from wetting to drying

Tong,

Pereira,

Huang

et al. 2023

Preprint

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Micro-computed tomography and low-field nuclear magnetic technologies were employed to investigate the evolution of the water occurrence and particle behaviors of the montmorillonite-kaolinite-quartz sand mixtures along a wetting-drying cycle. During the wetting-drying process, the total saturation was linearly related to the sample height. The cutoff values between the adsorbed water, capillary water and bulk water were roughly determined as 2.5 ms and 50 ms, respectively. In the wetting stage, the swelling under lower water content was dominated by adsorbed water, but it mainly depended on the linear increase in capillary water under higher water content. In the drying stage, the water distribution along the height was divided into apparent dry region, capillary flow region and saturated region. With continuous drying, the first region gradually expanded and the second reduced. Compared with nondeformable porous media, the range of them was smaller. If further dried to 5% water content, there will be only adsorbed water. The capillary water content was found to be linear with the sample height during drying. Consequently, the inconsistency of swelling-shrinkage deformations was mainly attributed to the hysteresis of capillary water. This work will provide basic experimental data and guidance for the subsequent simulations and theoretical model.

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Section: Specimen Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study on the microscopic swelling-shrinking mechanisms of clay-sand mixtures from wetting to drying

Tong,

Pereira,

Huang

et al. 2023

Preprint

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“…By contrast, the inert quartz, carbonate or feldspar grains (mainly from the COx claystone) were embedded into the clay matrix [13]. Generally, the small intra-grain pore volume in inert minerals could be ignored [22] and the abovementioned inter-particle pores were resident in the clay matrix.…”

Section: Inter-particle Distance and Its Relationship To Swelling Pre...mentioning

confidence: 99%

Evaluation of swelling pressure of bentonite/claystone mixtures from pore size distribution

2022

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The swelling behaviour of expansive clays is strongly related to the interaction between clay particles. In this paper, a series of constant-volume swelling pressure and mercury intrusion porosimetry (MIP) tests were carried out on MX80 bentonite/Callovo-Oxfordian (COx) claystone mixtures with different bentonite fractions and dry densities. Results show that the swelling pressure increased linearly with the increase of dry density. Additionally, at a given dry density, the larger the bentonite fraction, the larger the swelling pressure. From the MIP results, the inter-particle pore volume decreased with the increases of bentonite fraction and dry density.To link the macroscopic swelling behaviour with the microstructure features, a new method was proposed, allowing the determination of the average inter-particle distance from the pore size distribution. Moreover, a linear relationship was identified between the swelling pressure and the average inter-particle distance in a semi-logarithmic plane, regardless of the bentonite fraction and montmorillonite content.

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“…Besides, Vergara (2019) documented a significant strength and stiffness reduction in overconsoliated clay shales after swelling. The majority of testing was carried out on intact samples, but the material behavior of remoulded and reconstituted clay shale has been increasingly studied recently, as mixtures of clay shale and bentonites are being investigated as a possible buffer material in the context of deep geological storage (Zeng et al 2021;Zhang and Kröhn 2019;Souza and Pejon 2020). For a characterisation of clay shales for in situ application, testing on intact specimens is essential, since processes that arise from the natural formation of the shale and diagenesis are hardly considered otherwise.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigations on Hydro-mechanical Processes in Reconstituted Clay Shale and Their Significance for Constitutive Modelling

et al. 2023

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The hydro-mechanical processes of a reconstituted clay shale (Opalinus Clay) were studied and implications for constitutive modelling of swellable clay shales derived. The study aims to provide further insights into these coupled processes. For that, oedometric swelling tests with varying boundary conditions and loading paths, oedometric compression tests under dry and saturated conditions, and permeability tests were performed. The results showed a unique preloading line for the dry state when plotting the void ratio against the vertical stress. For saturated states, this line was shifted to the left (to smaller stresses) which revealed a severe reduction of preloading stress due to saturation. All loading paths converged in a normal compression line (NCL) regardless of the mechanical boundary conditions during saturation. A trend line affine to the NCL was established for swelling pressures at different initial void ratios. The influence of saturation on the mechanical properties became further evident, as the un-/reloading stiffness was significantly reduced. A linear relationship between volumetric deformation and saturation was found. A severe swelling induced reduction of permeability in the saturated state was demonstrated and confirmed by the analysis of consolidation processes during oedometric loading. The experimental findings were used to derive fundamental assumptions for constitutive modelling and were discussed within a numerical framework for expansive soils.

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Pore size distribution and swelling behavior of compacted bentonite/claystone and bentonite/sand mixtures

Cited by 11 publications

References 27 publications

Experimental study on the microscopic swelling-shrinking mechanisms of clay-sand mixtures from wetting to drying

Experimental study on the microscopic swelling-shrinking mechanisms of clay-sand mixtures from wetting to drying

Evaluation of swelling pressure of bentonite/claystone mixtures from pore size distribution

Experimental Investigations on Hydro-mechanical Processes in Reconstituted Clay Shale and Their Significance for Constitutive Modelling

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