Rheological‐stiffness analysis of K+‐treated and CaCO3‐rich soils

Abstract

AbstractRheological methods are applied whenever flow behavior of substances needs to be investigated on a particle‐to‐particle scale executed by a parallel‐plate rheometer. Under oscillation, mechanical effects due to trafficking or vibrations caused by agricultural and forest machinery can be simulated by conducting amplitude‐sweep tests. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr‐Coulomb's equation, and, finally, Bingham's yielding are well‐known relationships and parameters in the field of rheology. This paper aims to introduce rheometry as a suitable method to determine the mechanical behavior of salt‐affected soils when subjected to external stresses. Potassium‐treated loamy sand from Halle and loamy silt from Kassel, both sites located in Germany, as well as loess from Israel, saturated with NaCl solutions in several concentrations were analyzed. From the stress‐strain–relationship parameters like the storage modulus G′ and the loss modulus G″, yield stress τy and the linear viscoelastic (LVE)–deformation range including the deformation limit γL, i.e., the transition from an elastic to a viscous state, were determined and calculated, respectively. With respect to salt effects, amplitude‐sweep tests on originally CaCO3‐rich Avdat Loess show an increasing stability if saturated with higher NaCl concentrations. Comparable tests with K+‐rich substrates from Halle and Kassel evinced similar tendencies including the phenomenon of a critical K+ content, which becomes more obvious in case of the drained (–60h Pa) loamy‐silt samples from Kassel. Nevertheless, a higher microstructural stability is given in both substrates from Halle and Kassel, affected by different water contents, in general, which influence the exchange and availability of cations. The results verify that oscillatory tests are applicable for retracing salt‐induced effects, beside those ones, which are influenced by texture, current water content, and/or further chemical parameters.