Class notes of Geotechnical Engineering course I used to teach at UET Lahore. Feel free to download the slide show. Anyone looking to modify these files and use them for their own teaching purposes can contact me directly to get hold of editable version.

1. 1
Geotechnical Engineering–II [CE-321]
BSc Civil Engineering – 5th Semester
by
Dr. Muhammad Irfan
Assistant Professor
Civil Engg. Dept. – UET Lahore
Email: mirfan1@msn.com
Lecture Handouts: https://groups.google.com/d/forum/geotech-ii_2015session
Lecture # 19
15-Nov-2017

2. 2
Terzaghi (1943) developed the theory for continuous/strip
foundations (simplest, 2D problem).
 BNNDNcq qfcult '5.0'' 
Contribution of:
Shear
strength
Surcharge
Soil self-
weight
 sBNNDsNcq qfccult '5.0'' 
General form of Terzaghi’s Bearing Capacity Theory
sc and sγ → shape factors
TERZAGHI’S BEARING CAPACITY THEORY

3. 3
 BNNDNcq qfcult '5.0'' 
TERZAGHI’S BEARING CAPACITY THEORY

4. 4
GENERAL BEARING CAPACITY
EQUATION
 After Terzaghi, several researchers worked in this area.
 Bearing capacity factors Nc and Nq do not change much.
 Nγ varies, mainly because of the assumption of the wedge
shape of soil immediately below the foundation.
Meyerhof (1963) presented a general form of bearing capacity
equation as follows;
 idsBNidsNDidsNcq qqqqfccccult '5.0'' 
sc, sq and sγ → shape factors
dc, dq and dγ → depth factors
ic, iq and iγ → inclination factors

5. 5
MEYERHOF’S BEARING CAPACITY
EQUATION
To be used with
Vesic’s equation
as well

6. 6
GENERAL BEARING CAPACITY
EQUATION
Hensen’s (1970) general bearing capacity equation;
 bgidsBNbgidsNDbgidsNcq qqqqqqfccccccult '5.0'' 
sc, sq and sγ → shape factors
dc, dq and dγ → depth factors
ic, iq and iγ → inclination factors
gc, gq and gγ → ground factors (based on ground slope)
bc, bq and bγ → base factors (tilted base)
Vesic (1975) general bearing capacity equation is identical, but
with slightly different factors.

7. 7
GENERAL BEARING CAPACITY EQUATION

8. 8
GENERAL BEARING CAPACITY
EQUATION

9. 9
Practice Problem #3
A square column foundation is to be designed for a gross
allowable load of 250 kN. If the load is inclined at an angle of
15° to the vertical, determine the width of the foundation. Take
a factor of safety of 3.0.  = 19 kN/m3, f’ =35°, and c’ = 5
kN/m2 the depth of foundation is 1.0 m.

10. 11
Practice Problem #4

11. 14
EFFECT OF GROUNDWATER TABLE
ON BEARING CAPACITY
Shallow groundwater affects
soil shear strength in two ways:
1. Reduces apparent cohesion
which is present in soil in
unsaturated state → may
necessitate reducing the
cohesion measured through
UCCT
2. Pore water pressure
increases → reduces both
effective stress and shear
strength in the soil

12. 15
Case-III
EFFECT OF GROUNDWATER TABLE
ON BEARING CAPACITY
Case-I Case-II

13. 16
Case I
Groundwater table is located
at a distance D above the
bottom of the foundation.
Case-I
 BNNDcNq qfcult 5.0
1. Modify γDf term as
γ(Df – D) + γsub.D
2. Modify 0.5γBNγ term as
0.5γsubBNγ
Where,
γsub = γsat - γw
EFFECT OF GROUNDWATER TABLE
ON BEARING CAPACITY

14. 17
Case II
Groundwater table is located
at the foundation base.
 BNNDcNq qfcult 5.0
1. No change to γDf term.
2. Modify 0.5γBNγ term as
0.5γsubBNγ
Where,
γsub = γsat - γw
Case-II
EFFECT OF GROUNDWATER TABLE
ON BEARING CAPACITY

15. 18
Case III
Groundwater table is located
at a depth D below the
foundation base.
 BNNDcNq qfcult 5.0
1. No change to γDf term.
2. Use γav in the third term;
γav = γ (for D > B)
γav = 1/B [γD + γsub (B – D)] (for D ≤ B)
γsub = γsat - γw
Case-III
EFFECT OF GROUNDWATER TABLE
ON BEARING CAPACITY

16. 19
CONCLUDED
REFERENCE MATERIAL
Foundation Analysis and Design (5th Edition)
Joseph E. Bowles
Chapter #4
Principles of Geotechnical Engineering (7th Edition)
Braja M. Das
Chapter #16