Experimental data have shown that subrounded to rounded
materials (Ottawa sands and glass beads) and subangular materials
(Valdosta blasting sands) sliding on FRP or steel exhibit
different shear stress–horizontal displacement behavior.
Rounded materials yield more ‘‘brittle’’ interface behavior
than do angular materials. Strain softening is more evident in
the characteristic shear stress–horizontal displacement behavior
for interfaces between rounded particles and relatively
rough surfaces. It was found that the peak interface friction
coefficient, mp, between granular material and FRP or steel
decreased with an increase of normal stress, sn, as a power
function mp = Csnm, which follows Archard’s elastic deformation friction theory. The constant C and the power index m
both depend on the angularity of particles and the surface
roughness of the FRP or steel.The interface friction coefficient,
mp, increased linearly with the relative roughness, Rn,
and was only slightly influenced by the initial density of the
soil specimen. Interface shear tests showed that the specimen
preparation method, the rate of shearing, and the thickness of
the soil specimen had little influence on the interface behavior.
FRP and steel materials exhibit similar relationships between
the peak interface friction coefficient and the relative roughness
for a given granular material. Accordingly, use of FRP
materials in foundation applications should be possible if appropriate
tests are performed to determine the interface characteristics
with the soils present at the site.