Granular Materials in Civil Engineering: Recent Advances in the Physics of Their Mechanical Behavior and Applications to Engineering Works - Multiscale Geomechanics: From Soil to Engineering Projects - page 57

2 with characteristic grain size D 2 tested under a confining stress, σ (2) , we have to
apply a confining stress on material 1 equal to:

D

σ (1) = σ (2) . [3.26]

2

D

1

− so, the shear strength envelope of the rockfill material ( D 1 = 150 mm) can be
obtained by a simple geometrical similarity applied on the shear strength envelope
of the gravel material ( D 2 = 12 mm) with a similarity factor equal to

12 1

≈

150 3.5

applied on the confining stress.

Figure 3.11. Shear strength envelopes for homothetic groups of materials:
a) original compilation by Barton; b) display of scale effects

Such transformed curves are plotted using dotted lines in Figure 3.11b by
extrapolating the data obtained for D Max = 12 mm in order to predict the properties
of a granular material with D Max = 150 mm. The comparison with experimental data
shows a quite satisfactory agreement. It appears, therefore, to be possible to
determine the shear strength of very coarse granular materials (here 150 mm
maximum) by using the results obtained on finer materials (here 12 mm maximum),
provided that they have the same mineral origin, parallel grain size distribution, and
the same density.

The original data reported by Barton come from an exceptional experimental
study by Marachi et al . [MAR 69] performed on three groups of materials: