The impact of strain rate on folding and boudinage under plane strain: Results from analogue modelling
Mengong, Mathurin Enama; Zulauf, Gernold
To demonstrate the impact of varying strain rates on growing folds and boudins under plane strain, we investigated a stiff layer consisting of non-linear viscous Kolb grey plasticine that is embedded in a weak matrix, consisting of non-linear viscous Beck's green plasticine. The strain rates used range from 8 × 10−6 s−1 to 2 × 10−2 s−1. The viscosity ratio between layer and matrix increases with strain rate from 3 to 10. Different runs have been carried out in which the layer (S) was oriented perpendicular to the principal strain axes (X>Y>Z). Our results suggest a considerable influence of the strain rate on the geometry of the deformed stiff layer including its thickness. A striking break in both the degree of layer thickening and the change in arc length of folds and boudins is obvious at a strain rate of 1 * 10−3 s−1, which corresponds to a viscosity ratio of ca. 7. The new results might be interesting for those workers who are dealing with deformed rock salt or melt-lubricated shear zones. In both of these cases the strain rates may vary significantly. The new results further confirm that analytical solutions do not hold for very low viscosity ratios between layer and matrix.