| dc.description.abstract | The cohesive character has been evaluated primarily in the field, where a pedologist is capable
to recognize it rather easily. However, there is a problem of subjectivity and lack of metrics for
characterization, so research has been done in order to address this doubt with quantitative
methods measured so far in the meso-scale. It is known that adhesion and cohesion processes
originate at the micro scale, that is, in the interactions between particles, and a useful method
to analyze the micro scale but not yet tested, is through rheometry. The objective of this study
was then to evaluate whether rheological properties, obtained in amplitude sweep tests under
oscillatory shear conditions, are able to detect the cohesive character and thus contribute to
improve the understanding of cohesiveness in these soils. In a rotational rheometer, samples of
six soil types were evaluated at three different positions in the profile (top, middle, and bottom),
with and without cohesive character. Several soil rheological properties were determined: strain
at the end of the linear viscoelastic range, LVR range (γLVR), shear stress at the end of the LVR
range (τLVR), strain at the yield point (YP) (γYP), storage and loss modulus at YP (G'G”YP),
maximum shear stress (τmax), strain at maximum shear stress (γ τ max), and z integral (Iz). In this
study, only a few rheological properties had a significant effect on detecting the cohesive
character of the soil, in general with higher values for cohesive soils compared to non-cohesive
soils, indicating that cohesive soils are more stable. While cohesion affected only the γ base
position of the rheological properties at the end of the LVR range, it had a significant effect on
the τmax and γ τ max properties, in the top and middle positions, respectively. In addition, three
materials did not reach the pour point. For the integral z, cohesive soils showed both lower and
higher values than non-cohesive soils. Greater Iz in non-cohesive soils seems to be linked to a
small expansion, a consequence of the high friction between the particles. In this sense, τmax
and Iz were the properties that had a significant double interaction between the factors analyzed.
The type of soil had the greatest effect on the rheological properties, being, in general, the PVAd
soil with the highest values. Within the other soil properties studied, iron, organic carbon and
clay content, density, and normal force at test initiation had the greatest impact on rheology.
The evaluated mesoscale property, tensile strength, showed the closest relationship with γ τ max
and τmax. It is concluded that rheometry can help identify the cohesive character supporting
other analyses, but for an independent evaluation, more tests, especially at different water
contents, are needed. | |
