9:00 AM - 9:15 AM
[PPS03-06] Relaxation process of regolith-covered terrains induced by vibration
Keywords:Regolith, Granular fluidization, Planetary terrain, Modification process of craters, Impact-induced seismic event
Experimental procedures are as follows: A sandpile having the angle of repose is made on a disk pasted with the same kind of grains. Then, sinusoidal vertical vibration is continuously applied to the system. During the vibration, the relaxation process of the shape of a sandpile is recorded by using a laser profiler.
According to the observations in experiments, the fluidization occurs when the maximum vibration acceleration exceeds the gravitational acceleration. In the analyses, relations between the flux and the slope of a heap are measured at a variety of time. As a result, the relation can be described by the phenomenologically-derived transport model on the basis of Ref. [3]. In this model, the thickness of a flowing layer is determined by the local height of a heap, whilst the transport velocity is detemined by the local slope of a heap, the granular friction coefficient, and the velocity characterizing the vibration strength. Then, from the experimental results obtained in various conditions, the characteristic velocity is found to be proportional to the maximum velocity of vibration.
In summary, by combining experiments and theoretical considerations, we have derived the transport law to describe the flux of a flow on a heap under vibration. In this relation, the thickness of a flowing granular layer is determined by the height of a sandpile , which is constrained by the experimental system size. Therefore, assuming that its thickness corresponds to the thickness of a flowing regolith layer, the vibro-relaxation dynamics of regolith-covered terrains would be described by the transport model proposed in this study.
[1] D. Tsuji and N. A. Teanby, Icarus 277, 39 (2016)
[2] J. E. Richardson et al., Science 306, 1526 (2004)
[3] J. J. Roering et al., Water Resour. Res. 35, 853 (1999); J. J. Roering et al., Geology 29, 143 (2001)