Civil Engineering Reference
In-Depth Information
Worked examples
Example 12.1: Calculation of strains for overconsolidated Cam clay
A soil has the para-
meters
M
0.05 and its behaviour can be represented by
the Cam clay model. A sample is isotropically compressed in a stress path triaxial cell
to
p
=
=
0.98,
λ
=
0.20 and
κ
=
g
=
300 kPa and swelled to
p
0
=
200 kPa where the specific volume is
v
0
=
2.13.
q
=
δ
p
=
It is then subjected to a drained test in which
δ
10 kPa.
, since the state of the
overconsolidated sample is inside the state boundary surface. Hence,
The strains are given by Eqs. (12.16) and (12.17) with
λ
=
κ
g
3
vp
δ
0.05
×
10
×
100
q
=
δε
=
=
0.04%
s
2.13
×
200
×
3
=
vp
δ
0.05
×
10
×
100
q
=
δε
=
0.11%
v
2.13
×
200
Example 12.2: Calculation of strains for normally consolidated Cam clay
A second
sample of the soil in Example 12.1 was isotropically compressed to
p
0
=
200 kPa
where the specific volume was
v
0
=
2.19. It was then subjected to a drained test in
q
=
δ
p
=
which
10 kPa.
The strains are given by Eqs. (12.16) and (12.17), with the initial state
p
=
δ
200 kPa,
η
=
v
0 corresponding to isotropic compression. The compliances given
by Eqs. (12.18) to (12.20) are
=
2.19 and
0.15
0.98
2
+
1
0.05
3
10
−
3
m
2
/kN
C
11
=
=
0.39
×
200
×
2.19
1
10
−
3
m
2
/kN
C
22
=
2.19
(
0.15
+
0.05
)
=
0.46
×
200
×
0.15
0.98
1
10
−
3
m
2
/kN
C
12
=
=
0.35
×
200
×
2.19
and, hence,
q
−
p
)
δε
=
(
C
11
δ
C
12
δ
×
100
=
0.74%
s
q
+
p
)
δε
=
(
C
12
δ
C
22
δ
×
100
=
0.81%
v
References
Britto, A. M. and M. J. Gunn (1987)
Critical State Soil Mechanics via Finite Elements
, Ellis
Horwood, Chichester.
Muir Wood, D. M. (1991)
Soil Behaviour and Critical State Soil Mechanics
, Cambridge
University Press, Cambridge.
Roscoe, K. H. And J. B. Burland (1968) 'On the generalised stress-strain behaviour of “wet”
clay', in
Engineering Plasticity
, J. Heyman and F. A. Leckie (eds), Cambridge University Press,
Cambridge.
Schofield, A. N. and C. P. Wroth (1968)
Critical State Soil Mechanics
, McGraw-Hill, London.
