Class 1 Moisture Content - Specific Gravity ( Geotechnical Engineering )

Civil Engineering - Texas Tech University
CE 3121: Geotechnical Engineering Laboratory
Introduction
Moisture Content, Unit Weight, Specific Gravity
and Phase Relationships
Abdulrahman Alhabshi
Sources:
Soil Mechanics – Laboratory Manual, B.M. DAS (Chapters 2 - 3)
1

 Handouts: Syllabus, Report Format
 Class website:
http://www.classes.ce.ttu.edu/ce3121/
 Significance of the Class
 Lab No.1: Moisture Content, Specific gravity
and Unit Weight of soil
 Background: Phase Relationship
Class Outlines
2

Syllabus
 Text books:
 Soil Mechanics: Laboratory
Manual by Braja M. Das
 Lecture Notes
 ASTM Standards 2005
 Class organization
 1 hour class
 2 hours lab
 Class Schedule (No classes Oct 18 & 19)
 Attendance
3

Report Format
 Each group will submit one report per lab
 Reports are due one day before the class at 9am
(Ex: for Wed. class, submit report on Tuesday at 9am)
 All reports should follow the report format
 Title and Table of Contents
 Purpose & Objective
 Apparatus & Procedures
 Deviation from ASTM Standards
 Table of results
 Figures
 Sample Calculations
 Discussion and Conclusion
4

Report Format - Conclusion
 Report your results (use a table)
 Do the results fall within the expected range
or not?
(Check tables and match your results)
 If not, Explain why (what went wrong?)
5

Significance of this Class
 Why do you need to learn about soils?
Almost all structures are either constructed
of soil, supported on soil, or both.
 Who must be concerned with soils?
Civil engineers (structural, environmental and
geotechnical) must have basic understanding
of the soil properties in order to use them
effectively in construction.
6

Transcosna Grain Elevator, Canada
Oct. 18, 1913
West side of foundation sank 24-ft 7

Settlement
Palacio de las Bellas, Artes,
Mexico City
Leaning Tower, Pisa
8

Shear Failure – Slope Stability
9

Organization of the Lab Tests
Physical
(Soil Characteristics)
Mechanical
Moisture
Content
Unit Weight
CompressibilityPermeability
Specific
Gravity
Gradation
Atterberg
Limits
Strength
(Shear)
Geotechnical engineering
Structural engineering
Pavement engineering
Environmental engineering
Geotechnical engineering
Structural engineering
Pavement engineering
Soil Properties
(Soil Classification)
10

Today’s Lab
 Determination of unit weight (density)
 Determination of moisture content
 Determination of specific gravity
 Establishing the phase (weight-volume)
relationship diagram
 Calculation of:
 Dry unit weight
 Void ratio
 Porosity
 Degree of saturation
11

1- Unit Weight, g
 Take several measurements for diameter and
height
 Take the average for H, D
 Calculate g
V
M
g
 H
D
V
where
4
2


H
D
12

2- Moisture Content, w
 Definition: Moisture content is an indicator of the
amount of the water present in soil.
 Moisture content, w(%)
 ASTM 2216 (Conventional Oven Method)
 ASTM D 4643 (Microwave Oven Method)
 3 minutes at 50% Power (mass ≈ 50 g)
 
T
w
s
w
M
M
notbut
M
M
w 100% 
Mw – Mass of waters
Ms – Mass of solids
MT – Total mass
13

2- Moisture Content – Sample Size
 Minimum mass of moist material selected to be
representative of the total samples:
Maximum Particle Size
(95-100% Passing)
Standard Sieve
Size
Recommended Min. Mass
of moist specimen
2 mm or less # 10 20 g
4.75 mm # 4 100 g
9.5 mm 3/8-in 50 g
19.0 mm ¾-in 250 g
37.5 mm 11/2 -in 1000 g
75.0 mm 3-in 5000 g
14

2- Moisture Content - Procedure
Video Demos

2- Moisture Content – Sample Calculation
16

3- Specific Gravity, Gs
 Definition; specific gravity, Gs, of soil solids is the
ratio of the density of the aggregate soil solids to
the density of water.
 Mathematically,
 ASTM D 854
 This method is applicable for soils composed of
“Particles smaller than 4.75mm in size”.
w
s
sws
w
w
s
s
w
s
s
M
M
GhenceVVbut
V
M
V
M
G


;

g w = 1 g/cm3 at 40C
or w = 62.4 lb/ft3
17

3- Specific Gravity – Sample Size
 The procedure employs Archimedes’s principle
“A body submerged in water will displace a volume of water equal to its own
volume.”
 The key to successful application of this procedure is the
removal of entrapped air
 Recommended mass for test specimen
Soil Type
Specimen Dry Mass (g)
250 mL Pycnometer
Specimen Dry Mass (g)
500 mL Pycnometer
SP, SP-SM 60 ± 10 100 ± 10
SP-SC, SM, SC 45 ± 10 75 ± 10
Silt or Clay 35 ± 5 45 ± 10
18

3- Specific Gravity - Apparatus
Report Gs in terms of GS (200C) = GS (Ti0C) x A
A – From Table 3-2 Pg 12
 See Example in Table 3-3 Pg 13
19
Video Demos

3- Specific Gravity – Expected Values
 Expected Values for Gs
Type of Soil Gs
Sand 2.65 - 2.67
Silty sand 2.67 – 2.70
Inorganic clay 2.70 – 2.80
Soils with mica or iron 2.75 – 3.00
Organic soils < 2.00
20

 Phase Relationships
 Three phase diagram
 Weight relationships
 Volumetric relationships
 Weight – Volume relationship
 Examples
Phase Relationships
21

Phase Relationships: A 3-Phase Material
Solid
Water
Air
22

The Mineral Skeleton
Volume
Solid Particles
Voids (air or water)
23

Three Phase Soil
(Partially Saturated)
Solids
Air
Water
Mineral Skeleton Idealization:
Three Phase Diagram
24

Two Phase Soil
(1) Fully Saturated Soils
Fully Saturated
Water
Solids
Mineral Skeleton
25

Two Phase Soil
(2) Dry Soils [Oven Dried]
Mineral Skeleton Dry Soil
Air
Solids
26

Weight-Volume Relationships
Volume Weight
Solids
Air
Water
WT
Ws
Ww
Wa~0
Vs
Va
Vw
Vv
VT
27

Weight Relationships (weight -ratios)
 Weight ratios
 Moisture Content, w
 Specific Gravity, Gs
 Weight Components:
 Weight of Solids = Ws
 Weight of Water = Ww
 Weight of Air, Wa ~ 0
%100(%), 
s
w
W
W
wContentWater
Solids
Air
Water
WT
Ws
Ww
Wa~ 0
28

Specific Gravity (weight ratio)
WaterofVolumeEqualanofWeight
ceSubsaofWeight
GravitySpecific
tan

WaterofWeightUnit
ceSubsaofWeightUnit
GravitySpecific
tan

%100, 
ws
s
w
s
s
s
V
WV
W
GGravitySpecific
gg
Unit weight of Water, gw or w
 gw = 1.0 g/cm3 (strictly accurate at 4° C)
 gw = 62.4 pcf
 gw = 9.81 kN/m3
29

Typical Values for Specific Gravity, Gs
30

Volumetric Relationships (Vol. ratios)
 Volumetric ratios
 Void ratio, e
 Porosity, n(%)
 Degree of Saturation, S (%)
 Volume Components:
 Volume of Solids = Vs
 Volume of Water = Vw
 Volume of Air = Va
 Volume of Voids = Va + Vw = Vv
Solid
Air
Water
Vs
Va
Vw
Vv
VT
31

Volumetric Relationships
s
v
V
V
eRatioVoid ,
%100(%), 
V
w
V
V
SSaturationofDegree
%100(%), 
T
v
V
V
nPorosity
32

Weight-Volume Relationships
 Steps to develop the weight-volume relationship
 Separate the three phases
 The total volume of a soil
 Assuming the weight of air (Wa) to be negligible, the
total weight is then given as
awsvs VVVVVV 
wsT WWW 
33

Example:
 Determine moisture content, void
ratio, porosity and degree of
saturation of a soil core sample.
Also determine the dry unit
weight, gd
Data:
 Weight of soil sample, MT = 1013g
 Vol. of soil sample, VT = 585.0cm3
 Specific Gravity, Gs = 2.65
 Moisture Content, w = 12.1%
34

Solid
Air
Water
Ma~0
Volumes Weights
1013.0g585.0cm3
904.0g
Gs =2.65
109.0g
341.1cm3
109.0cm3
243.9cm3
134.9cm3
gw
= 1.0 g/cm3
Sample Calc.
gMMM sTw 1099041013 
3
9.134)1091.341(585)( cmVVVV wsTa 
3
3
109
)/(0.1
)(109
cm
cmg
gW
V
V
W
w
w
w
w
w
w 
g
g 3
3
1.341
)/(0.165.2
)(904
cm
cmg
g
G
W
V
V
W
G
ws
s
s
ws
s
s 


gg
gVVV awv 9.2439.134109 
35
g
w
M
M
MwMMwM
insubstitute
MwM
M
M
wbut
MMM
T
s
sssT
sw
s
w
swT
904
121.01
1013
1
)1(
)1()2(
)2(
)1(










w
=12.1%

Sample Calculation (cont.)
g
w
M
M
MwMMwM
insubstitute
MwM
M
M
wbut
MMM
T
s
sssT
sw
s
w
swT
904
121.01
1013
1
)1(
)1()2(
)2(
)1(










gVVV awv 9.2439.134109 
3
3
1.341
)/(0.165.2
)(904
cm
cmg
g
G
W
V
V
W
G
ws
s
s
ws
s
s 


gg
3
3
109
)/(0.1
)(109
cm
cmg
gW
V
V
W
w
w
w
w
w
w 
g
g
3
9.134)1091.341(585)( cmVVVV wsTa 
gMMM sTw 1099041013 
1
2
3
4
5
6
36

Weight-Volume Relationships (cont.)
 From the previous figure we can find:
 Moisture content, w
 Void ratio, e
 Porosity, n
 Degree of saturation, S
 Dry unit weight, gd 3
55.1
585
904
cm
g
V
W
T
s
d g
%7.44100
9.243
109

v
w
V
V
S
715.0
1.341
9.243
3
3

cm
cm
V
V
e
s
v
%7.41100
)(0.585
)(9.243
3
3

cm
cm
V
V
n
T
v
%1.12100
)(904
)(109

g
g
W
W
w
s
w
37

Weight-Volume Relationships (cont.)
38

Typical Unit weights
39

40

This Report Should Include
1. Unit Weight of Soil, g
2. Water Content, w
3. Specific Gravity, Gs
4. Three Phase Diagram
5. Void ratio, e
6. Porosity, n
7. Degree of Saturation, S
8. Dry Unit Weight, gd
41

Class 1 Moisture Content - Specific Gravity ( Geotechnical Engineering )

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