1. 1
CE-313 (2 Credit Hours)
Geotechnical Engineering-II
Introduction to Course and
Concept of Effective Stress
Instructor:
Prof- Dr Irshad Ahmad
Fall 2020
Department of Civil Engineering
University of Engineering and Technology, Peshawar
2. In this course following chapters will be discussed;
Chapter 1 Effective Stress Concept
Chapter 2 Consolidation
Chapter 3 Shear Strength of Soil
Chapter 4 Slope Stability
Chapter 5 Lateral Earth Pressure
2
Introduction to course
11. Course Title: Geotechnical Engineering-II
Course Code: CE–313
Course Duration: One Semester
Credit Units: 02 Credit Hrs.
Level: 5th Semester, 3rd Year
Medium of Instruction: English
Prerequisites: Geotechnical Engineering-I
Equivalent Courses: Not Applicable
11
Geotechnical Engineering-II
CE-313
(course specification form)
Part I: Course Information
12. 12
Course Aims
After this course the students will
1. Understand the shear and consolidation behavior of soils and determination of
relevant soil parameters using laboratory tests.
2. Carry out slope stability analysis
3. Find lateral earth pressures
Course Intended Learning Outcomes (CLOs)
1. Define effective stress, Shear strength of soil, soil consolidation and lateral
earth pressure parameters, and different slope failures.
2. Explain Response of effective soil to changes in total stress, different shear
failure theories, laboratory and field tests for shear strength consolidation
parameters determination, consolidation process, lateral earth pressure
theories, and slope stability methods.
3. Apply the consolidation parameters to estimate amount and time rate of
settlement, lateral earth pressure theories to find lateral earth pressures, and
shear strength parameters to field conditions
Evaluate the stability of slopes
Course Aims, Course Intended Learning Outcomes (CLOs)
13. 13
Course learning outcomes will be achieved through a combination of the following
teaching strategies.
Quizzes
In-class activities
Video presentations
Reading assignments
Classroom discussions
Homework assignments
Mid-term major examination
Final comprehensive examination
Solved examples in the classroom
Conducting tutorials in the classroom
Teaching and Learning Activities (TLAs)
14. 14
WEEK TOPIC CLOs Quiz/Assignm
ent
1 Principle of effective stresses, Effective Vertical Stress due to self
weight of the soil, Response of Effective Stresses to a change in total
stress, Spring Analogy
1,2
2 1D Consolidation, Oedometer Test, e- curve, e-log() curve, OCR,
OCC, and NCC, Compression index, recompression index,
Determination of Preconolidation Pressure by Casagrande Method
1,2 Assignment-1
3 Schmertmann Procedure to obtain in-situ e-log() curve, coefficient
of volume compressibility, Consolidation settlement calculations for
NCC and OCC
1,2
4 Solved Examples 3 Quiz-1
5 Degree of Consolidation, Average degree of consolidation, Terzaghi’s
theory of 1D consolidation
12,3
6 Solution of consolidation equation, Isochrones, Determination of Cv
by Log-time method (due to Casagrande) and Root time method (due
to Tylor)
1,2,3
7 Solved Examples 3 Assignment-2
8 Importance, Shear strength of soil, Coulomb’s Theory, Modified
Coulomb’s Theory, Mohr-Coulomb Failure Criterion, Tresca
Failure Criterion
1,2 Quiz-2
9 MID TERM EXAM
Weekly schedule
15. 15
10 Direct Shear Test, Peak, Ultimate, and Residual Shear Strengths, Solved
Examples
2
11 Triaxial Compression Test (UU, CU, and CD), Solved Examples. 1,2 Assignment-
3
12 Application of UU, CU, and CD Tests to field conditions, Unconfined
compression Test, Drained and Undrained Shear Strength, Shear Strength
of Sand, Liquefaction,
1,2,3
13 Behavior of NC and OC clays in drained and undrained test, Mohr’s
Circles for OC and NC clays under CU tests, Failure envelop for OC clays,
Types of Analysis for OC and NC clays, Vane Shear Test
2.3 Quiz-3
14 Active, Passive and At-Rest Earth Pressures, Lateral Strain Vs Earth
Pressure, Rankine’s Lateral Earth pressure theory
1.2
15 LEP for surcharge loads, stratified Soil, Drained & undrained Analysis,
Sloping soil surface, Solved Examples on Rankine’s Theory, Coulomb’s
Theory of Earth pressures
1,2,3 Assignment-
4
16 Types of Slope Failure, limit equilibrium method, Slope stability analysis
for u=0 soil, Taylor Stability Number, Solved Examples clays and clayey
silts
1,4
17 Method of Slices with Swedish and Bishop Routine Solutions, Plane
Translational Slip, Solved Examples
1,4 Quiz-4
18
Final Term Exam
Weekly schedule
16. 16
ATAs CLOs Weight % Remarks
Final-Term Exam 1-4 50% 2 hrs written exams
Mid-Term Exam 1-3 25% 2 hrs written exams
Home Assignments 1-4 10% Total 4 assignments
Quizzes 1-4 15% Total 4 in-class tests
Total (%) 100 % The final grading is relative
Assessment Tasks Activities (ATAs)
Indicative of likely activities and tasks designed to assess how well students achieve
the CLOs. Final details will be provided to students in their first week of attendance in
this course.
Assessment Tasks Activities (ATAs)
17. 17
Grade
Letter
Grade
Points
Grade Definitions
A
A-
4.0
3.67
Excellent
Strong evidence of original thinking; good organization,
capacity to analyze & synthesize; superior grasp of subject
matter; evidence of extensive knowledge base.
B+
B
B-
3.33
3.00
2.67
Good
Evidence of grasp of subject, some evidence of critical capacity
and analytical ability; reasonable understanding of issues;
evidence of familiarity with literature.
C+
C
C-
2.33
2.00
1.67
Adequate
Student who is profiting from the university experience;
understanding of the subject; ability to develop solutions to
simple problems in the material.
D+
D
1.33
1.00
Marginal
Sufficient familiarity with the subject matters to enable the
student to progress without repeating the course.
F 0.00 Failure
Little evidence of familiarity with the subject matter; weakness
in critical and analytical skills; limited, or irrelevant use of
literature.
Grading of Students Achievements
The grading for this course is based on the Academic Regulations criterion of the
University.
Assessment Tasks Activities (ATAs)
18. 18
Syllabus
Chapter-01: Effective Stress
Chapter-1 Effective Stress
Principle of effective stresses, Effective Vertical Stress due to self weigth of the soil,
Response of Effective Stresses to a change in total stress, Spring Analogy
Chapter-2 Consolidation
1D Consolidation, Oedometer Test, e- curve, e-log() curve, OCR, OCC, and NCC,
Compression index, recompression index, Determination of Preconolidation Pressure
by Casagrande Method
Schmertmann Procedure to obtain in-situ e-log() curve, coefficient of volume
compressibility, Consolidation settlement calculations for NCC and OCC
Part III: Syllabus, Recommended Books, Online Sources, Course Coordinator
19. 19
Chapter-3 Time Rate of Consolidation Settlement
Degree of Consolidation, Average degree of consolidation, Terzaghi’s theory of 1D
consolidation
Solution of consolidation equation, Isochrones, Determination of Cv by Log-time
method (due to Casagrande) and Root time method (due to Tylor), solved examples
Chapter-4 Shear Strength of Soil
Importance, Shear strength of soil, Coulomb’s Theory, Modified Coulomb’s
Theory, Mohr-Coulomb Failure Criterion, Tresca Failure Criterion
Direct Shear Test, Peak, Ultimate, and Residual Shear Strengths, Solved
Examples
Triaxial Compression Test (UU, CU, and CD), Solved Examples.
Application of UU, CU, and CD Tests to field conditions, Unconfined compression
Test, Drained and Undrained Shear Strength, Shear Strength of Sand,
Liquefaction,
Behaviour of NC and OC clays in drained and undrained test, Mohr’s Circles for
OC and NC clays under CU tests, Failure envelop for OC clays, Types of Analysis
for OC and NC clays, Vane Shear Test
Part III: Syllabus, Recommended Books, Online Sources, Course Coordinator
20. 20
Chapter-5 Lateral Earth Pressures
Active, Passive and At-Rest Earth Pressures, Lateral Strain Vs Earth Pressure,
Rankine’s Lateral Earth pressure theory
LEP for surcharge loads, stratified Soil, Drained & undrained Analysis, Sloping soil
surface, Solved Examples on Rankine’s Theory, Coulomb’s Theory of Earth
pressures
Chapter-5 Slope Stability
Types of Slope Failure, limit equilibrium method, Slope stability analysis for u=0
soil, Taylor Stability Number, Solved Examples clays and clayey silts
Method of Slices with Swedish and Bishop Routine Solutions, Solved Examples
Plane Translational Slip, Solved Examples
Part III: Syllabus, Recommended Books, Online Sources, Course Coordinator
21. 21
Dr. Irshad Ahmad
Professor
Civil Engineering Department
UET Peshawar, Khyber Pakhtunkhwa.
irspk@yahoo.com
Office Location:
CE: A209,
Civil Engineering Department,
UET Peshawar.
Recommended Books and References
1.Soil Mechanics by R.F Craig
2.Soil Mechanics and Foundations by Muni Budhu
Online Resources
1.Watch online videos/animations for shear and consolidation tests.
Course Coordinator
Part III: Syllabus, Recommended Books, Online Sources, Course Coordinator
23. 23
CONTENTS
• Introduction
• Principle of effective stress
• Effective vertical stress due to self weight of soil
• Response of effective stress to a change in total
stresses
• Consolidation and its analogy
• Examples
28. A saturated layer of clay 4 m thick is overlain by sand 5m
deep, the water table being 3m below the surface. The
saturated unit weights of the clay and sand are 19 kN/m3 and
20 kN/m3 , respectively; above the water table the unit weight
of the sand is 17 kN/m3 . Plot the values of total vertical stress
and effective vertical stress against depth. If sand to a height
of 1 m above the water table is saturated with capillary water,
how are the above stresses affected.
28
Example 3.1 (SM by R.F. Craig)
5 m
4 m
3 m
Sand
=17kN/m3
clay
29. 29
5 m
4 m
3 m
Sand
=17kN/m3
clay
3m
5m
0m
9m
sat =19 kN/m3
sat =20 kN/m3
-
17*3=51
91+19*4=167
51+20*2=91
17*3=51
91-19.6=71.4
167-58.86=108.2
9.81*2=19.6
9.81*6=58.86
Total stresses
(kPa)
Effective
stresses (kPa)
Pore water
Pressure(kPa)
30. 30
5 m
4 m
3 m
Sand
=17kN/m3
ꞌ=17 kN/m3
clay
sat =19 kN/m3
ꞌ (19-9.8)=9.19
sat =20 kN/m3
ꞌ(20-9.8)=10.2
(17-0)*3=51
51+10.2*2=71.4
71.4+9.2*4=108.2
Effective stresses (kPa)
ꞌ=ꞌ z = (sat - w) z
Alternate Method
0m
3m
5m
9m
32. The water table is at level at which pore water is at
atmospheric (u=0). Above the water table water is held
under negative pressure and even if the soil is saturated
above the water table, does not contribute to hydrostatic
pressure below the water table. The only effect of one
meter capillary rise is, therefore, to increase the total unit
weight of sand between 2 and 3 meter depth from 17 to 20
kN/m3 ,an increase of 3 kN/m3 . Both total and effective
stresses below 3 meter depth are therefore increased by the
same amount 3x1 = 3.0 kN/m2, pore water pressures, pore
water pressures being unchanged.
32
5 m
4 m
3 m
sand
clay
1 m
When soil 1 m above water table is saturated by capillary rise
=17 kN/m3
sat =20 kN/m3
sat =19 kN/m3
35. 35
Spring Analogy
Spring soil skeleton
water Pore water in soil
Bore diameter permeability of soil
Rigid cylinder walls zero lateral
Strain in soils
39. z
39
Response of Effective Stress to a change in total stress
us =w z = hydrostatic pwp
ꞌo =o –us= effective stress
o=sat z = total stress
40. z
t=0 (undrained condition with ue=ui)
u= us + ∆
v ≠0
l 0
∆ Change in total stress
ue=ui = Initial Excess pore water
pressure
ui ∆
ꞌꞌo
o +∆
ꞌ +u= ꞌ+(us+∆)
ꞌ = ꞌo
40
∆ ~ q
41. z
u= us + ue
41
@ t > 0 (Dissipation of Excess PWP)
u=us+ue
ue Excess pore water pressure at
t>0
ue < ui
ꞌo > ꞌ & ꞌ ꞌo +(∆-ue )
Drainage
∆s
ꞌ > ꞌo
∆
time
time
0
u
us
ꞌo
ꞌ
∆
o
o
t
42. z
u us
ue = Excess pore water pressure at
t= tf & ue =0
ꞌ ꞌo +∆
42
@ t = tf (Drained Condition ue=0)
u
o =sat z
sf
ui
∆
us
0
time
time
ꞌo
ꞌ
t=tf
∆
43. 43
Terminology Learnt
• Total stresses
• Effective stresses
• Static Pore water Pressure
• Excess Pore Water Pressure
• Dissipation of excess PWP
• Drainage of Pore water
• Fully Saturated soil
• Drained and Undrained condition
• One dimensional Consolidation
44. 44
Example 3.2
A 5 m depth of sand overlies a 6 m layer of clay, the
water table being at the surface; the permeability of the
clay is very low. The saturated unit weight of the sand is
19 kN/m3 and that of clay is 20 kN/m3. A 4 m depth of
fill material of unit weight 20 kN/m3 is placed on the
surface over an extensive area.
Determine the Effective vertical stress , Total Vertical
stress , pore water pressure (u) at the center of the clay
layer;
(a) Immediately of after the fill has been placed,
assuming this to take place rapidly and
(b) Many years after the fill has been placed
4 m Fill
20kN/m3
5 m
6 m
sand
8 m
3 m
sat 19kN/m3
Clay
sat 20kN/m3
45. Change in Total Stress = ∆ = 4 x 20 = 80 kPa
(a) Immediately After Construction
Total Vertical Stress
v = o+∆
v (19*5)+(3*20)+80= 235 kPa
Effective Vertical Stress
Since clay is of low permeability, all the ∆ (change in
total stress) is taken by pore water as excess pore water
pressure. Hence no increase in the effective stress due
to ∆
ꞌv 5*(9.2)+(3*10.2)=76.6 kPa
Static PWP (us)
us 9.8*8=78.4 kPa
Excess PWP (ue)
ue∆ 80 kPa
Total PWP (u)
u us+∆ 78.4+80=158.4 kPa
4 m
5 m
6 m
8 m
3 m
Fill
20kN/m3
Sand
sat 19kN/m3
ꞌ9.2 kN/m3
Clay
sat 20 kN/m3
ꞌ10.2 kN/m3
Solution
46. 46
Solution
(b) Long time after the fill has been placed
Total Vertical Stress
v ꞌ+(us+ ∆)= 235 kPa
Effective Vertical Stress
After long time the excess PWP will dissipate and the change in stress (∆) will be
taken by the soil skeleton and hence an increase of 80 kPa in effective will occur.
ꞌv 76.6+80 = 156.6 kPa
us9.8*8 78.4 kPa
Static PWP (us)
us 9.8*8=78.4 kPa
Excess PWP (ue)
ue= 0
Total PWP (u)
u = us78.4 kPa
