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Phase RelationsN. Sivakugan
Duration: 6 min 31 s
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Objectives
To compute the masses (or weights) and
volumes o the three di!erent phases.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
NotationM = mass or weight
V = volumes = soil grains
w = water
a = air
v = voids
t = total
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"e#nitions
$ater content (w)is a measure othe water present in the
soil.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
S
W
M
Mw=
Expressed as percentage.
ange = ! " 1!!#$.
% 1!!$
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"e#nitions
%oid ratio (e)is a measure o thevoid volume.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
S
V
V
Ve =
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"e#nitions
Porosit& (n)is also a measure o the void
volume' epressed as a percentage.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
T
V
V
Vn = % 1!!$
Theoretical range * +,**-
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"e#nitions
"egree o saturation (S)is the percentage
o the void volume #lled b& water.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
V
W
V
VS=
Range * +,**-
,**-
Dr
& 'aturate
d
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/ Simple 0ample
water
air
soil
1n thisillustration'
e 2 ,
n 2 3*-
S 2 3*-
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"e#nitions
4ulk densit& (m)is the densit& o the soil
in the current state.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
T
T
m
V
M=
(nits: t)m3* g)ml* +g)m3
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"e#nitionsSaturated densit& (sat)is the densit& o the
soil
when the voids are #lled with water.
Submerged densit& (5)is the e!ective
densit& o the soil when it is submerged.
5 2 sat6 w
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"e#nitions
"r& densit& (d)is the densit& o the soil in
dr& state.
soil
air
water
Vs
Va Ma=0
Ms
MwMt
Vw
Vv
Vt
Phase Diagram
T
S
d
V
M=
(nits: t)m3* g)ml* +g)m3
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"e#nitions
4ulk' saturated' dr& and submergedunitweights ()are de#ned
in a similar manner.
2 g
7ere' use weight (kN) instead o mass(kg).
Speci#c gravit& o the soil grains (8s)
t&picall& varies between 9.: and 9.;.
+g)m3N)m3 m)s,
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Phase Relations
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Phase Relations>rom the previous de#nitions'
soil
air
water
1 Gsw
Sew
See
Phase Diagram
SS
W
G
Se
M
Mw ==
e
e
V
Vn
T
V
+==1
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Phase Relations
soil
air
water
1 Gsw
Sew
See
Phase Diagram
W
S
T
T
m
e
SeG
V
M
+
+==
1
W
S
T
T
sat
e
eG
V
M
+
+==
1
W
S
T
S
d
e
G
V
M
+==1
C i h 2001
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Tr& not to memorisethe e?uations.Understandthe de#nitions'
and develop therelations rom the phase diagram with %S2 ,@
/ssume 8S(9.:69.;) when not given@
"o not mi densities and unit weights@Soil grains are
incompressible. Their massand volume remain the same at an&
voidratio.
C i h 2001
i
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/ Suggestion..
- &ou can remem/er one thing inphase relations* that should
/e ..
1 Gsw
SewSe
e
soil
air
water
C i ht2001
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Testing TimesA
'tate whether the ollowing are true or alse0
(a) Dry density is greater than submerged density
(b) In unsaturated soils, water content is always less
than 100%.
(c) Larger the void ratio, larger the porosity.
rue
2alse
rue
