Numerical Modeling: An Efficient Tool for Analyzing the Behavior of Constructions - Multiscale Geomechanics: From Soil to Engineering Projects - page 303

308 Multiscale Geomechanics

100

φ int =30°

80

60

40

20

z= 1.61 m
z= 4.61 m

0

0 50 100 150 200

σ n (kPa)

(a) (b)

(c) (d)

Figure 9.29. Stress path in the interface at different depths, for soils with
three different relative densities ( D r = 93, 40 and 24%): TS93, TS40 and TS24:
effect of the initial state of the soil clump

or on the total load applied. When the load on the pile head is removed, the vertical
movement of the pile may be sufficient to generate a negative skin friction along the
pile (Figure 9.30). If the pile is reloaded again and the force-displacement curve at the
pile head is compared for the first and second cycles, the effect of the residual friction
can be observed.

When applying several cycles of loading-unloading, the observed behavior depends
on the load level. Thus, three mechanisms of friction degradation can be identified,
depending on whether the maximum friction is reached during the first cycle, only
the phase transformation (characteristic state) is reached, or neither of the two limits
is reached. These scenarios correspond, by analogy, to the process of pile installation