[PPS03-P08] Experimental study on effect of cohesive force on dynamical evolution of regolith layer due to vibration
Keywords:regolith, vibration, filling factor, compaction
In this study, we investigate the effect of cohesive force on the compaction behavior of granular material due to vibration. We used particles smaller than 100 μm as sample powder to mimic the magnitude of effect of interparticle force acting on the particles on asteroids. Sample powder was sieved into a sample die. Samples were tapped by the free fall of the sample die. The vibrational acceleration applied to the sample was controlled by falling height of the die and recorded by an accelerometer which is attached to the die. The maximum acceleration of the pulsed wave ranged from ~150 to 500 m/s2 (Γ=~15-50). Samples were tapped 10, 30, 50, and 100 times and the filling factor of the sample before and after tapping was calculated from the volume and mass of the samples.
We use spherical glass beads with diameter of 18 μm as one of powder sample. The filling factor of the sample before tapping was ~0.43. The filling factor of sample after 100 times tapping increased with Γ. The filling factor increased with the number of tapping at all cases with different Γ and didn’t achieve the equilibrium even when the sample was tapped 100 times. On the other hand, in previous study (Phillipe and Bideau 2002), 100 times tapping is enough to achieve the equilibrium filling factor when the applied tapping acceleration was larger than Γ~3 (Phillipe and Bideau, 2002). It means that the acceleration larger than Γ=50 is needed to achieve the equilibrium filling factor by 100 times tapping for the powder bed consisting of cohesive particles. It is suggested that under the microgravity environment, where the interparticle force is dominant, the value of Γ that characterizes the phenomena due to vibration may change in orders of magnitude.