The Peak Strength of Sand-Steel Interfaces and the Role of Dilation

Abstract

ABSTRACT Sand-steel interface tests have been performed using a modified direct shear apparatus that enables accurate dilation measurements to be taken. Average roughness and maximum roughness, when divided by D50, are equally good at correlating both friction and dilation data. Below a certain relative roughness threshold, interface behaviour is non-dilatant. Above that threshold, interfaces show classical stress-dilatancy behaviour, with peak values following a simple flow rule. When peak interface friction and dilation angles are normalised by dividing by equivalent direct shear values, dilatant interface test data covering a range of particle sizes, relative densities and surface roughnesses fit a simple linear model when plotted against relative roughness on a logarithmic scale. When relative roughness reaches an upper limit, interface behaviour becomes fully rough, reproducing peak friction and dilation angles in direct shear. Normalised peak interface friction ratios are likely to range between 0.5 and 1.0 for sand on rolled steel surfaces, with the value depending primarily on particle size.