Rheological properties of different minerals and clay soils

Abstract

Rheological properties of kaolinite, montmorillonite, ferralitic soil of the humid subtropics (Norfolk island, southwest of Oceania), alluvial clay soil of arid subtropics (Konyaprovince, Turkey) and carbonate loess loam of Russian forest-steppe zone were determined. A parallel plate rheometer MCR-302 (Anton Paar, Austria) was used in order to conduct amplitude sweep test. Rheological properties allow to assess quantitatively structural bonds and estimate structural resistance to a mechanical impact. Measurements were carried out on samples previously pounded and capillary humidified during 24 hours. In the amplitude sweep method an analyzed sample was placed between two plates. The upper plate makes oscillating motions with gradually extending amplitude. Software of the device allows to receive several rheological parameters such as elastic modulus (G’, Pa), viscosity modulus (G", Pa), linear viscoelasticity range (G’>>G”), and point of destruction of structure at which the elastic modulus becomes equal to the viscosity modulus (G’=G”- crossover). It was found out that in the elastic behavior at G '>> G " strength of structural links of kaolinite, alluvial clay soil and loess loam constituted one order of 10⁵ Pa. Montmorillonit had a minimum strength - 10⁴ Pa and ferrallitic soil of Norfolk island [has] - a maximum one -10⁶ Pa. At the same time montmorillonite and ferralitic soil were characterized by the greatest plasticity. Destruction of their structure (G '= G") took place only in the cases when strain was reaching 11-12%. Destraction of the kaolinite structure happened at 5% of deformation and of the alluvial clay soil and loess loam - at  4.5%.

Keywords

• soil mechanics, soil structure, rheology, storage modulus, loss modulus, linear viscoelastic range

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