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 75

and passing through the CC line, these small shear movements are distributed within
the rockfill mass, with mostly random orientation but with some polarization along
two characteristic directions. Those shear movements are predominantly clockwise
in the granular mass above the left abutment and predominantly anticlockwise above
the right abutment. They are in mixed directions in the central part of the valley.
Figure 3.21. Settlement micromechanisms in concrete faced rockfill dam body
In the vicinity of the perimetric joint:
− if the abutment slope is sufficiently flat (detail A in Figure 3.21b), the slip lines
resulting from the shear movements are intercepted at short distance by the
foundation. Therefore, the associated shearing cannot extend over a long distance
and, as a consequence, the deflection line of the concrete slab near the perimetric
joint will be regular and progressive;
− if the abutment slope is very steep (detail B in Figure 3.21b), the slip lines are
no longer intercepted at a short distance by the foundation; they can extend over a
long distance and, therefore, develop a localized shear band at the point of contact
with the abutment. The result is a concentrated differential settlement of the concrete
slab relative to the plinth, localized at the perimetric joint and resulting in a step in
the deflexion line of the slab, right at the perimetric joint.
For usual values of friction between the blocks in the rockfill, the corresponding
critical abutment slope is about 60° to 65° (without a safety margin). Mitigation