Prediction of swelling characteristics of compacted GMZ bentonite in salt solution incorporating ion-exchange reactions
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Salt solutions have complex effects on the swelling characteristics of compacted bentonite; these effects are caused by the inhibitory action of salinity and the ion-exchange reaction between the solution and bentonite. In order to characterize the swelling properties of compacted bentonite in a salt solution, swelling deformation tests were carried out for Gao-Miao-Zi (GMZ) bentonite specimens in NaCl and CaCl2 solutions. Swelling characteristics decreased with increasing salt concentration. Swelling strains in NaCl solution were larger than those in CaCl2 solution, even though the ionic concentration of 1.0 mol/L (M) NaCl solution is larger than that of 0.5 M CaCl2. According to the exchangeable cations tests, cation exchange was different for specimens immersed in different salt solutions. The swelling fractal model was used to predict the swelling strains of compacted bentonite in a concentrated salt solution. In this model, the effective stress incorporating osmotic suction was applied to take the effect of salinity into consideration, and the swelling coefficient, K, was employed to describe the swelling properties affected by the variation in exchangeable cations. In the model, fractal dimension was measured by nitrogen adsorption, and the salt solution had little effect on fractal dimension. K was estimated by the diffuse double layer (DDL) model for osmotic swelling in distilled water. Comparison of fractal model estimations with experimental data demonstrated that the new model performed well in predicting swelling characteristics affected by a salt solution.
KeywordsBentonite Fractal Model Ion-exchange Reaction Salt Solution Swelling Characteristics
The National Natural Science Foundation of China (Grants No. 41702311, No. 41630633, and No. 41877211) and the Nature Science Foundation of Anhui province of China (Grant No. 1708085QE99) are acknowledged for their financial support. The authors thank the reviewers and editors for their comments on this manuscript.
- ASTM. (2010). Standard test method for measuring the exchange complex and cation exchange capacity of inorganic fine-grained soils. ASTM D7503–D7510.Google Scholar
- Dohrmann, R., Kaufhold, S., & Lundqvist, B. (2013). The role of clays for safe storage of nuclear waste. Pp. 677–710 in: Handbook of Clay Science, Techniques and Applications (F. Bergaya and G. Lagaly, editors). Developments in Clay Science, Vol. 5B, Elsevier, Amsterdam.Google Scholar
- Ferrage, E., Lanson, B., Sakharov, B. A., Geoffroy, N., Jacquot, E., & Drits, V. A. (2007). Investigation of dioctahedral smectite hydration properties by modeling of X-ray diffraction profiles: Influence of layer charge and charge location. American Mineralogist, 92, 1731–1743.CrossRefGoogle Scholar
- Iwata, S., Tabuchi, T., & Warkentin, B. P. (1988). Soil–water interactions (pp. 131–166). New York: Marcel Dekker, Inc..Google Scholar
- Schramm, L. L., & Kwak, J. C. T. (1982a). Influence of exchangeable cation composition on the size and shape of montmorillonite particles in dilute suspension [J]. American Journal of Hypertension, 12(4), 41.Google Scholar
- Xu, Y. F., Matsuoka, H., & Sun, D. A. (2003) Swelling characteristics of fractal-textured bentonite and its mixtures. Applied Clay Science, 22(4), 197–209.Google Scholar
- Zheng, L., Rutqvist, J., Birkholzer, J. T., & Liu, H. H. (2015). On the impact of temperatures up to, 200°C in clay repositories with bentonite engineer barrier systems: A study with coupled thermal, hydrological, chemical, and mechanical modeling. Engineering Geology, 197, 278–295.CrossRefGoogle Scholar