Course
Year
: S0825/Foundation Engineering
: 2009
INTRODUCTION
Session 1 – 2
GENERAL
SCOPE OF THE COURSE
• Introduction (Definition, type of foundation, review of Soil Mechanics
Principles)
• Bearing Capacity of Soil
• Shallow foundations (type, design and settlement of foundation)
• Sheet Pile Structure (lateral earth pressure, design of sheet pile)
• Deep Foundation (Single pile, Group pile, settlement of pile)
• Installation of pile and test of pile capacity
• Application of shallow, deep foundation and sheet pile structure
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GENERAL
Grading Policy
• Home Work ………........................
• Mid Semester Test ……………….
• Final Test …..................................
TOTAL .....................
20%
30%
50%
100%
Note:
• Appropriate changes to this grading policy may be made with
student consent.
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REFERENCE TEXTBOOK
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REFERENCE TEXTBOOK
SUPPORTING
TEXTBOOK
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COURSE 1
Content:
• Definition
• Design Criteria
• Soil investigation, laboratory tests and soil
properties related to structure designs
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DEFINITION
What is Foundation Engineering?
The art of selecting, designing, and constructing
structural support systems based on scientific
principles of soils and engineering mechanics
incorporating accumulated experience with such
applications.
A scientifically Acceptable Answer
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DEFINITION
What is Foundation Engineering?
Foundation Engineering is the art and science of
molding materials we do not fully understand into
shapes we can not precisely analyze to resist
forces we can not accurately predict, all in such a
way that the society at large is given no reason to
suspect of our ignorance.
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Not so scientifically Acceptable Answer – addopted from Coduto
Retaining
Structure
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FOUNDATION TYPES
• Shallow Foundations.
Shallow foundations are usually placed within a depth D beneath the
ground surface less than the minimum width B of the foundation.
Shallow foundations consist of spread and continuous footings, wall
footings and mats.
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FOUNDATION TYPES
• Deep Foundations.
Deep foundations can be as short as 15 to
20 ft or as long as 200 ft or more and
may consist of driven piles, drilled shafts
or stone columns. A single drilled shaft
often has greater load bearing capacity
than a single pile. Deep foundations may
be designed to carry superstructure loads
through poor soil (loose sands, soft clays,
and collapsible materials) into competent
bearing materials. Even when piles or
drilled shafts are carried into competent
materials, significant settlement can still
occur if compressible soils are located
below the tip of these deep foundations.
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DESIGN CRITERIA
THE DESIGN SHOULD BE:
- SAFE
- RELIABLE
- DURABLE
- BUILDABLE
- ECONOMIC
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DESIGN DATA
•
•
•
•
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SOIL DATA
GROUND WATER DATA
GEOMETRY DATA
DATA OF LOAD
SOIL DATA
DETERMINED FROM:
- FIELD INVESTIGATION
-
CPT
SPT
VANE SHEAR TEST
PRESSUREMETER TEST
- LABORATORY TEST
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INDEX TEST
TRIAKSIAL
DIRECT SHEAR
UNCONFINED
CONSOLIDATION
STANDARD PENETRATION TEST (SPT)
• ADVANTAGES
– Could be used to identify soil types visually
– Could be used to get qualitative soil properties by empirical
correlation
• LIMITATION
– The soil strength profile can not be measured continuously
– The high accuracy is needed during investigation in case of
weight and fall height of hammer
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HAMMER OF SPT
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DIMENSION OF SPT TUBE
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SPT EXECUTION
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SPT PROFILE (EXAMPLE)
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CONE PENETRATION TEST (CPT)
• TYPES OF TOOL AND PRINCIPLE OF WORK
– Mechanical friction-cone penetrometer
by pushing a cone with projection area 10 cm2 and 60o angle
and standard velocity 20 mm per-second.
2 measurement parameters each 20 cm of depth:
• Cone Resistance (qc)
• Local Friction (fs)
– Electric friction-cone penetrometer
measure the cone pressure and continuously friction with
better accuracy level
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CONE PENETRATION TEST (CPT)
• ADVANTAGES
– Continuous Soil strength profile
– Give fast description of soil
– Simple
• LIMITATION
– The accuracy is bad for soil with some stones
– Mechanical friction-cone penetrometer is less
sensitive when applied in very soft clay
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CONE DIMENSION (ASTM D3441)
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ELECTRIC CONE DIMENSION
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CPT RESULT (EXAMPLE)
DUTCH CONE PENETRATION TEST
DUTCH CONE PENETRATION TEST
Friction Ratio (%)
Friction Ratio (%)
0
20
(5)
(5)
(10)
(10)
(15)
(20)
10
20
(15)
(20)
(25)
(25)
Cap. of equipment
Date of test
Water level
End of test
Cap. of equipment
Date of test
Water level
End of test
: 2.50 ton
: January, 11, 2009
: -4.50 m
: -13.70 m
: 2.50 ton
: January, 10, 2009
: -5.75 m
: -14.20 m
(30)
(30)
0
50
Cone Resistance (kg/cm2)
Local Friction (kg/cm2)
100
150
200
250
300
4
8
12
1000
2000
3000
0
50
Cone Resistance (kg/cm2)
Local Friction (kg/cm2)
100
150
200
250
300
4
8
12
1000
2000
3000
Total Friction (kg/cm)
Total Friction (kg/cm)
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0
0
Depth Below Ground Level (m)
Depth Below Ground Level (m)
0
10
Point No. : S-01
Point No. : S-02
LABORATORY TESTS
• Soil Index (, , e, GS dll.)
– Measuring of volume and mass of sample
– Sieve analysis test
– Atterberg Test
• Shear Strength of Soil (c, )
– Triaksial Test (UU, CU, CD)
– Direct Shear
– Unconfined Compression Test
• Compressibility (Cc, Cv)
– Consolidation Test
• Permeability (k)
– Constant Head
– Falling Head
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EMPIRICAL CORRELATION
• SPT Data
Sandy Soil
Clay or Silt
N-Value
Relative Density
N-Value
Consistency
0–4
Very loose
0–2
Very soft
4 – 10
Loose
2–4
Soft
10 – 30
Medium
4–8
Medium stiff
30 – 50
Dense
8 – 15
Stiff
> 50
Very dense
15 – 30
Very stiff
> 30
Hard
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EMPIRICAL CORRELATION
• CPT Data
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EMPIRICAL CORRELATION
• Between Soil Properties
– Cc = 0,009 (LL – 10)
– Cu = qu/2
– Cu = 19 – 23 CBR (C in kN/m2)
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