Layering effects of sand samples prepared by travelling pluviators

Travelling pluviators have been commonly adopted to prepare large-scale laboratory sand samples for higher efficiency and consistency. Despite several literature reviews investigating the superiority of such travelling pluviators being able to produce repeatable models, the complex interdependence of the operating variables, in particular travelling speed, on the prepared sand model has not been fully understood to date. In this study, various operating variables of the pluviator – the falling height, deposition intensity (i.e. sand flow rate from orifice) and travelling speed – are studied with three types of sands prepared to desired densities. Through a proposed hypothesis based on energy, the travelling speed was found to have little impact on the sand particles’ kinetic energy for deposition; the influence of the travelling speed on the relative density is realised by altering the layer thickness during pluviation. In addition, it is worth noting that, although the global uniformity can be achieved by preparing sand models in layers in a consistent manner, there exists non-uniformity within each pour in the vertical direction due to particles segregation. This study provides such detail by direct observation of the particle segregation within the layer and the extent of the disturbance by boundary effect of the container.