1327
Technical Committee 202 /
Comité technique 202
stress, initial effective confining pressure, and degree of
saturation on the permanent axial strain response of pond ash
are studied. In order to study the effect of applied cyclic
deviatoric stress on the permanent axial strain response, results
of tests performed at same initial effective confining pressure
but different deviatoric stress for the specimen compaction dry
unit weight,
d
= 10.64 kN/m
3
(RC = 95%) are plotted in Fig. 2.
It is observed that at a constant initial effective confining
pressure the applied cyclic deviatoric stress showed a
considerable influence on the permanent axial strain. Higher the
cyclic deviatoric stress higher is the permanent axial strain at
the same initial effective confining pressure. With increase in
applied cyclic deviatoric stress the variation in permanent axial
strain is observed to be less for high initial effective confining
pressure. For example, with increase in applied cyclic deviatoric
stress from 71.27 to 203.64 kPa, the corresponding increase in
permanent axial strain is approximately 85%, at initial effective
confining pressure,
3
c
= 35 kPa.
Figure 2. Relationships between permanent axial strains versus applied
cyclic deviatoric stress
Fig. 3 shows the effect of initial effective confining pressure
on the permanent axial strain response, at same applied cyclic
deviatoric stress but different initial effective confining
pressures for same reconstituted dry unit weight/density.
Figure 3. Relationships between permanent axial strains versus initial
effective confining pressure
It may be observed from the figure that the applied cyclic
deviatoric stress has a significant effect on permanent axial
strain at low initial effective confining pressure. High value of
permanent axial strain is observed at low initial effective
confining pressure. The permanent axial strain decreases as the
initial effective confining pressure increases and the decrease is
more pronounced at high applied cyclic axial deviatoric stress.
For example, with increase in initial effective confining
pressure from 15 kPa to 35 kPa, the corresponding decrease in
permanent axial strain value is approximately 89%, at an
applied cyclic deviatoric stress,
d
= 152.73 kPa.
The variation of permanent axial strain is plotted in Fig. 4 for
three degrees of saturation, for initial effective confining
pressure,
3
c
= 25 kPa and applied cyclic deviatoric stress,
d
=
127.27 kPa. The degree of saturation of the specimen during the
test was kept same as the degree of saturation during
compaction. It may be observed that with increase in degree of
saturation, a significant increase in permanent axial strain
values is obtained. The increase in permanent axial strain is
gradual up to the degree of saturation corresponding to the
MDD and is more rapid beyond this value. It is observed that
the permanent axial strain increases by 57.80% as the degree of
saturation increased from
S
r
= 52.7% to
S
r
= 77.71%.
Figure 4. Relationships between permanent axial strains versus degree
of saturation at compaction stage (without a back pressure saturation)
The effect of degree of saturation during shearing on
permanent axial strain response of pond ash is shown in Fig. 5.
Figure 5. Relationships between permanent axial strains versus degree
of saturation (with back pressure saturation)
Tests were conducted at the degree of saturation maintained
during compaction stage (
S
r
= 52.70%) and increased to
S
r
=
65%, 75%, 85%, 90%, and 95% respectively, before shearing.
