Environmental Engineering Reference
In-Depth Information
develop some intergranular stresses. The peak “undrained” strength parameters mobi-
lized depend on the soil type:
Cohesionless soils — the envelope passes through the origin (Figure 3.26 and
Figure 3.27) and strength is expressed in terms of
●
φ
as in equation 3.23.
Soils with cohesion — the envelope intercepts the shear stress ordinate at a value
taken as cohesion
c
, similar to the case shown in
Figure 3.28
,
and the strength is
expressed by the
Mohr-Coulomb
failure law:
●
s
c
σ
n
tan
φ
(3.24)
d
Effective
stress
Total
stress
FIGURE 3.26
Mohr's envelopes for total and effective
stresses from CU triaxial tests on loose
saturated sands.
P
3
u
df
P
1
u
df
P
3
P
1
d
Total stress
Effective
stress
FIGURE 3.27
Mohr's envelopes for total and effective stresses
from CU triaxial tests on dense saturated sands.
u
df
u
df
P
1
Normal stress P
P
3
P
1
P
1
c
σ
FIGURE 3.28
Drained triaxial test on soil with cohesion.
Confining, applied and normal stresses
