As discussed earlier, the initial density of sand has a significant
influence on its internal friction. For example, the results
of the DSTs summarized in Fig. 3 show that the difference
in the peak friction angle for VBS-A from a loose state
to a dense state is about 107. However, the peak interface friction
angle is less influenced by the initial density, as observed
from the results of interface tests between FRP or steel and
sand, shown in Fig. 12. The difference in the peak interface
angle for these interfaces is less than 37. Lehane et al. (1993)
had reported that the interface friction between steel and sand
is dependent on the initial density of sand