Viscous grain-grain interaction is an important aspect of the dynamics of oscillating sheetflow. This interaction between sand grains has been investigated qualitatively in a pulsating water tunnel. Furthermore, experiments concerning the interaction between neutrally buoyant spheres in a Couette flow have been carried out at a scale of 100:1 in a new developed ring shear apparatus, called " Carrousel." With respect to the dynamics of sheetflow, in-situ measuring devices for the sand concentration in the sheetflow ("Harp") and the bed load ("Swan") has been developed; some preliminary results are shown. For sand grains, the intrusion depth of sheetflow appears to be of the order of several mm. On high speed video recordings no lateral mixing between grain layers can be observed; for this some physical explanation is given. This supports the modelling of the sheetflow mechanism as moving grain layers.