  The determination of the mechanical properties of soils containing particles
larger than the allowable size by standard laboratory equipment is problematic.
It is indeed necessary to eliminate the coarsest fraction to carry out the
tests, which poses a problem of representativeness of the results at the scale
of the structure. Parallel gradation and scalping methods are presented as a
means of estimating the shear strength of heterogeneous granular soils from
tests on their finer fraction. This study focuses on the effect of fines
content on the estimation by these methods, which is not well known. The
results showed that the parallel gradation method can predict the angle of
friction of the initial material despite a high percentage of fines. However,
the cohesion of the initial material was overestimated. As for the scalping
method proposed by Fragaszy et al., the higher fines content in the modelled
material resulted in an overestimation of the cohesion and an underestimation
of the friction angle of the initial material.
