Investigation of piping material

Abstract

The grain size distribution of the material washed out from the piping under flood load, newer investigated earlier. Using 20 samples originating from different places at Danube and Tisza rivers, the grading characteristics of these samples were investigated on the basis of some selected grain sizes and the uniformity gradients. Based on these investigations it has become possible to identify which grain size fractions are likely to be washed out, and to characterise those fractions whose washing out is not expected. Based on the grain size distribution curves it has been made possible to define the boundaries of the zone susceptible to piping. The zone limits of granular soils liquefied by earth quakes and the zone limits of the soil outwashed from piping are very similar. This apparent correspondence already formerly raised the hypothetic question of whether piping occurring during high flood can be simulated by shape to similar surface liquefaction phenomena experienced during earth quakes, as in both cases a volcanic cone is formed through the crater of which water is constantly issuing, dragging away solid particles. Recently the apparent similarity of the zones of grain size distribution curves in the two cases strongly suggest that the two phenomena should indeed be closely related.