Transcript Slide 1

LINTON UNIVERSITY COLLEGE
SCHOOL OF CIVIL ENGINEERING
GEO-MECHANICS
(CE2204)
Engineering Properties of Soils
Lecture Week No 1
Nur Syazwani
SOIL MODEL AND BASIC PROPERTIES
Air
Water
Solid
Soil
Phase Diagram
THREE-PHASE SOIL MODEL
Ma ≈ 0
Volumes
Air
Va= e(1-S)
e
Mw = wGsρw
Water
Vw= Se = wGs
Ms = Gsρw
Solid
Vs = 1
Specific volume, V= 1+e
Masses
DEFINITION
Water content (w) is a measure of the amount of
water present in the soil
Ma = 0
Mw = wGsρw
Ms = Gsρw
Air
Water
Solid
Va= e(1-S)
Vw= Se = wGs
Vs = 1
M W Se
w

M S Gs
DEFINITION
Void ratio (e) is a measure of the void volume; it
may be occupied by either water and/or air
Ma = 0
Air
Va= e(1-S)
e
Mw = wGsρw
Ms = Gsρw
Water
Solid
Vw= Se = wGs
Vs = 1
Va  Vw
e
Vs
DEFINITION
Porosity (n) is also a measure of the void volume
to the total volume
Ma = 0
Air
Va= e(1-S)
e
Mw = wGsρw
Ms = Gsρw
Water
Vw= Se = wGs
Solid
Vs = 1
Vv
e
n

V 1 e
DEFINITION
Degree of saturation (S) is the fraction of the void
volume filled by water
Ma = 0
Mw = wGsρw
Ms = Gsρw
Air
Water
Solid
Va= e(1-S)
Vw= Se = wGs
Vw
S
Vv
Vs = 1
S=0
S=1
for perfectly dry soil
for fully saturated soil
DEFINITION

Mass
Volume
Air
  g    9.81103
e(1-S)
e
wGsρw
Water
Se = wGs
Gs ρ w
Solid
1
GS
d 
W
1 e
GS  Se
B 
W
1 e
 sat
GS  e

W
1 e
Example 1
A cylindrical specimen of moist clay has a diameter of 38 mm, height of
76 mm and mass of 174.2 grams. After drying in the oven at 105oC for
about 24 hours, the mass is reduced to 148.4 grams. Find the dry
density, bulk density and water content of the clay. Assuming the specific
gravity of the soil grains as 2.71, find the degree of saturation.
Example 2
Field density testing has shown bulk density of a compacted road base
to be 2.06 t/m3 with water content of 11.6%. Specific gravity of the soil
grains is 2.69. Calculate the dry density, porosity, void ratio and degree
of saturation.
Example 3
5 kg of soil, at natural water content of 3%, is to be mixed with water to
achieve water content of 12%. How much water would you add to the
above soil?
Example 4
Soil excavated from a borrow is being used to build an embankment.
The void ratio of the soil at the borrow is 1.14 and the porosity of the
compacted soil in the embankment is 40%. If the volume of excavation is
200,000 m3, how many cubic metres of embankment can be built using
this soil?