Final Examination: CIVL3100
Department of Civil Engineering
Dalhousie University
Examiner: Dr. Craig Lake, P.Eng.
December 9, 2004
Instructions
1)
This is a closed book examination. You are allowed a
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Phase relationships
Soil is a three phase material which consists of solid particles which make up th
CE 2113
Chapter One
Soil Mechanics I
Instructor: Dr. Hany El Naggar
Basic Characteristics of Soils
Plasticity of Fine Soils
Plasticity is an important characteristic in the case of fine soils, the ter
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Solution:
Lets take the datum at the drain level. This makes the total head at the top of the ground surface
=
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
SEEPAGE
Darcys law can be used only to calculate the one directional flow of water through soil. In
many insta
6. Unit weights
W
V
2845 10 6 kN
157.1 10 6 m 3
Ws
V
2327.9 10 6
157.1 10 6
bulk
dry
. kN / m 3
181
14.8 kN / m 3
If the sample were saturated there would need to be an additional 14.9 106 m3 of wate
CE 2113
Chapter One
Soil Mechanics I
Instructor: Dr. Hany El Naggar
Basic Characteristics of Soils
Example 5:
A sample of soil is taken using a thin walled sampling tube from a soil deposit. After the
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Some important rules for drawing flow nets:
Draw scaled crosssection of problem, defining all boundaries due
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Grain Size Distribution
In any soil mass the sizes of the grains varies to a great extent. To classif
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Example 1:
A long horizontal drain is located at 4 m below the ground surface. The drain collects the
ground w
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
kN/m3
Unit Weight
To sufficient accuracy the density of water rw is given by
w
= 1000 kg/m3= 1 g/cm3
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
In general, Soil Mechanics is one of the youngest disciplines of Civil Engineering involving
the stud
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Moisture content
The moisture content, w, is a very useful quantity because it is simple to measure.
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
We can use Gs to calculate the density or unit weight of the solid particles
s
= Gs
w
s
= Gs
w
and he
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Example 1:
The results of particle size analysis of a soil sample are shown in Table 2. Determine the
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
To assess the degree of compaction it is important to use the dry unit weight,
dry,
because we are
in
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Bernoullis Equation
h
z
Datum
Figure 2: Groundwater flow
Bernoullis equation states that for steady flow of no
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
From the figure
=4
N = 2.5 and N = 8 respectively.
The seepage loss of the dam per meter length of dam is
=
=
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
LABORATORY DETERMINATION OF PERMEABILITY
Permeability of a coarse grained soil can be determined by the consta
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Darcys Law
Darcy (1856) found that the flow rate (laminar flow) in a porous medium (e.g. soil) is:
i. Proporti
CE 2113
Soil Mechanics I
Chapter Four
Instructor: Dr. Hany El Naggar
Consolidation
The solution of the governing differential equation is written in terms of
2
=
Where
(2
as:
sin
is the initial excess
CE 2113
Chapter Five
Soil Mechanics I
Shear Strength of Soil
Instructor: Dr. Hany El Naggar
o
Frictional resistance between particles (stress dependent component)

This component is dependent of norm
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Laboratory Compaction tests
There are several types of test which can be used to study the compaction
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
Plasticity index
The plasticity index (PI) is a measure of the plasticity of a soil. The plasticity i
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Solution:
The impermeable boundaries: along sheet piling BCD and along the impermeable stratum GG;
thus, BCD a
CE 2113
Chapter One
Soil Mechanics I
Basic Characteristics of Soils
Instructor: Dr. Hany El Naggar
hence a relationship between
=
dry
and w for a given value of A can be derived as follows
1+
( +
+
=
CE 2113
Soil Mechanics I
Chapter Three
Instructor: Dr. Hany El Naggar
Effective Stress
Effective Stress in the Ground
Ground movements and instabilities can be caused by changes in total stress (such
CE 2113
Chapter Two
Soil Mechanics I
Seepage and Flow nets
Instructor: Dr. Hany El Naggar
Example 2:
A sheet pile is driven 7 m into a homogeneous sandy soil 12 m thick. The sand is underlain by an
im
Example 5:
Solution
1. Distribution by mass and weight
Phase
Trimmings
Mass
(g)
55
45
10
Total
Solid
Water
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
290
237.3
52.7
2845 106
2327.9 106
517 106
2. Di