SlideShare a Scribd company logo
1 of 86
Download to read offline
INTERNATIONAL UNIVERSITY
FOR SCIENCE & TECHNOLOGY
‫وا‬ ‫م‬ ‫ا‬ ‫و‬ ‫ا‬ ‫ا‬
CIVIL ENGINEERING AND
ENVIRONMENTAL DEPARTMENT
303322 - Soil Mechanics
Stress Distribution in Soil
Dr. Abdulmannan Orabi
Lecture
2
Lecture
7
Dr. Abdulmannan Orabi IUST 2
Das, B., M. (2014), “ Principles of geotechnical
Engineering ” Eighth Edition, CENGAGE
Learning, ISBN-13: 978-0-495-41130-7.
Knappett, J. A. and Craig R. F. (2012), “ Craig’s Soil
Mechanics” Eighth Edition, Spon Press, ISBN: 978-
0-415-56125-9.
References
Stress in soil due to self weight
Stress Distribution in Soil
Stress in soil due to surface load
3Dr. Abdulmannan Orabi IUST
Stress due to self weight
The vertical stress on element A can be determined
simply from the mass of the overlying material.
If represents the unit weight of the soil, the
vertical stress is
Variation of stresses with depth
A
Ground surface
zz ⋅= γσ
	
	 	 	
4Dr. Abdulmannan Orabi IUST
∑=
⋅=⋅++⋅+⋅=
n
i
iinnz hhhh
1
2211 ...... γγγγσ
Stress due to self weight
Stresses in a Layered Deposit
The stresses in a deposit consisting of layers of
soil having different densities may be determined as
Vertical stress at depth z1
Vertical stress at depth z2
Vertical stress at depth z3
∗
∗ ∗
∗
∗ ∗
∗ ∗ ∗
5Dr. Abdulmannan Orabi IUST
With uniform surcharge on infinite land surface
Stress due to self weight
Original
land surface
Conversion land surface
∗ 	
	 	 	
	
	
	 	 	
6Dr. Abdulmannan Orabi IUST
Stress due to self weight
∗
Vertical stresses due to self weight increase
with depth,
There are 3 types of geostatic stresses:
a. Total Stress, σtotal
b. Effective Stress, σ'
c. Pore Water Pressure, u
Vertical Stresses
7Dr. Abdulmannan Orabi IUST
Stress due to self weight
Consider a soil mass having a horizontal
surface and with the water table at surface
level. The total vertical stress at depth z is
equal to the weight of all material (solids +
water) per unit area above that depth ,i.e
Total vertical stress
!"!#$ %#! ∗
8Dr. Abdulmannan Orabi IUST
Stress due to self weight
The pore water pressure at any depth will be
hydrostatic since the void space between the solid
particles is continuous, therefore at depth z:
Pore water pressure
& ∗
If the pores of a soil mass are filled with water
and if a pressure induced into the pore water, tries
to separate the grains, this pressure is termed as
pore water pressure
9Dr. Abdulmannan Orabi IUST
Stress due to self weight
Effective vertical stress due to self weight of soil
The difference between the total stress ( !"!#$) and
the pore pressure (u) in a saturated soil has been
defined by Terzaghi as the effective stress ( ).'
'
!"!#$	 −
The pressure transmitted through grain to grain at
the contact points through a soil mass is termed as
effective pressure.
10Dr. Abdulmannan Orabi IUST
Stress due to self weight
Stresses in Saturated Soil
If water is seeping, the effective stress at any
point in a soil mass will differ from that in
the static case.
It will increase or decrease, depending on the
direction of seepage.
The increasing in effective pressure due to the
flow of water through the pores of the soil is
known as seepage pressure.
11Dr. Abdulmannan Orabi IUST
A column of saturated soil mass with no seepage of
water in any direction.
The total stress at the
elevation of point A can be
obtained from the saturated
unit weight of the soil and
the unit weight of water
above it. Thus,
Stress due to self weight
Stresses in Saturated Soil without Seepage
0
A
Solid particle
Pore water
)*
)&
+
+
12Dr. Abdulmannan Orabi IUST
0
A Solid particle
Pore water
)*
)&
+
+
+
+
Forces acting at the points of contact of soil
particles at the level of point A
Stress due to self weight
Stresses in Saturated
Soil without Seepage
	 &	) ,)* − )- %#!
where
+ 	 . 	+ 	 	
/+ 	 	0 	1
%#! + .+ 2	 	 	
	 	
)* 2 + 3 	4 	0
	1	+ 2	 	 + .	 +4 	
13Dr. Abdulmannan Orabi IUST
Stress due to self weight
Stresses in Saturated Soil without Seepage
)
)
5
6
7
8
Valve (closed)
Stress at point A,
• Total stress:
• Pore water pressure:
• Effective stress:
* 	 &	)
* 	 &	)
*
'
	 * − * 0
Stress at point B,
• Total stress:
• Pore water pressure
• Effective stress:
: 	 &	) ) 	 ∗ %#!
: 	,) ) 	- &
:
'
	 : − :
:
'
	) %;<
14Dr. Abdulmannan Orabi IUST
Stress due to self weight
Stresses in Saturated Soil without Seepage
Stress at point C,
• Total stress:
= 	 &	) ∗ %#!
> 	,) - &
>
'
	 > − >
>
'
%;<
• Pore water pressure:
• Effective stress:
Total stress
Pore water
Pressure, u Effective stress
DepthDepth Depth
15Dr. Abdulmannan Orabi IUST
)
)
5
6
7
8
Valve (open)
?
(
@
AB
-
Stress due to self weight
Stresses in Saturated Soil with Upward Seepage
Stress at point A,
• Total stress:
• Pore water pressure:
• Effective stress:
* 	 &	)
* 	 &	)
*
'
	 * − * 0
16Dr. Abdulmannan Orabi IUST
Stresses in Saturated Soil with Upward Seepage
Stress due to self weight
Stress at point B,
• Total stress:
• Pore water pressure
• Effective stress:
: 	 &	) ) 	 ∗ %#!
: 	,) ) 	 - &
:
'
	 : − :
:
'
	) %;< − 	 &
17Dr. Abdulmannan Orabi IUST
Stresses in Saturated Soil with Upward Seepage
Stress due to self weight
Stress at point C,
• Total stress:
• Pore water pressure:
• Effective stress:
= 	 &	) ∗ %#!
: 	,)
)
- &
>
'
	 > − >
>
'
%;< −
)
	 &
>
'
%;< − 	 	 &
Note that h/H2 is the hydraulic gradient i
caused by the flow, and therefore
18Dr. Abdulmannan Orabi IUST
Total stress
Pore water
Pressure, u Effective stress
DepthDepth Depth
Stress due to self weight
Stresses in Saturated Soil with Upward Seepage
19Dr. Abdulmannan Orabi IUST
Stress due to self weight
Stresses in Saturated Soil with Upward Seepage
At any depth z, is the pressure of the
submerged soil acting downward and is the
seepage pressure acting upward.
The effective pressure reduces to zero when these two
pressures balance.
This situation generally is referred to as boiling.
>
'
%;< − >C	 	 & 0
>C
%;<
&
. 		 >C 3. 3+ 	 D2.+ 3	 .+2
For most soils, the value of >C	varies from 0.9 to 1.1
%;<
	 	 &
>
'
20Dr. Abdulmannan Orabi IUST
)
)
5
6
7
8
Valve (open)
?
(
@
AB
-
Stress due to self weight
Stresses in Saturated Soil with Downward Seepage
Stress at point A,
• Total stress:
• Pore water pressure:
• Effective stress:
* 	 &	)
* 	 &	)
*
'
	 * − * 0
21Dr. Abdulmannan Orabi IUST
Stress at point B,
• Total stress:
• Pore water pressure
• Effective stress:
: 	 &	) ) 	 ∗ %#!
: 	,) ) 	 − - &
:
'
	 : − :
:
'
	) %;< 	 &
Stress due to self weight
Stresses in Saturated Soil with Downward Seepage
22Dr. Abdulmannan Orabi IUST
Stress due to self weight
Stress at point C,
• Total stress:
• Pore water pressure:
• Effective stress:
= 	 &	) ∗ %#!
: 	,) −
)
- &
>
' 	 > − >
>
'
%;<
)
	 & >
'
%;< 	 	 &
Stresses in Saturated Soil with Downward Seepage
23Dr. Abdulmannan Orabi IUST
Pore water
Pressure, uTotal stress Effective stress
DepthDepth Depth
Stress due to self weight
Stresses in Saturated Soil with Downward Seepage
24Dr. Abdulmannan Orabi IUST
Worked Examples
Example 1
A soil profile is shown in figure below. Calculate total
stress, pore water pressure, and effective stress at A,
B, C, and D.
D
C
B
A Ground surface
G.W.T
Sand
Clay
Sandγ = 16.3 kN/m^3
γ = 15.1 kN/m^3
γ = 19.8 kN/m^3
1.8 m
1.6 m
2.9 m
25Dr. Abdulmannan Orabi IUST
Stress due to self weight
Total stress Effective stress Pore water pressure
DepthDepthDepth
γ1 X H1
γ1 X H1 + γ2 X H2
γ1 X H1 + γ2 X H2 + γ3 X H3
γ1 X H1 + γ2 X H2 + γsub X H3
γw X Hw
26Dr. Abdulmannan Orabi IUST
To analyze problems such as compressibility of
soils, bearing capacity of foundations, stability
of embankments, and lateral pressure on earth
retaining structures, we need to know the
nature of the distribution of stress along a
given cross section of the soil profile.
Stress due to surface load
Introduction
27Dr. Abdulmannan Orabi IUST
When a load is applied to the soil surface, it
increases the vertical stresses within the soil
mass. The increased stresses are greatest
directly under the loaded area, but extend
indefinitely in all directions.
Introduction
28Dr. Abdulmannan Orabi IUST
Stress due to surface load
•Allowable settlement, usually set by building
codes, may control the allowable bearing
capacity.
•The vertical stress increase with depth must
be determined to calculate the amount of
settlement that a foundation may undergo
Introduction
29Dr. Abdulmannan Orabi IUST
Stress due to surface load
Introduction
Foundations and structures placed on the
surface of the earth will produce stresses in
the soil
These stresses will decrease with the
distance from the load
How these stresses decrease depends upon
the nature of the soil bearing the load
30Dr. Abdulmannan Orabi IUST
Stress due to surface load
Individual column footings or wheel loads
may be replaced by equivalent point loads
provided that the stresses are to be
calculated at points sufficiently far from
the point of application of the point load.
Stress Due to a Concentrated Load
31Dr. Abdulmannan Orabi IUST
Stress due to surface load
Stresses in soil due to surface load
Vertical stress due to a concentrated load
• Boussinesq’s Formula
• Wastergaard Formula
Stress Due to a Concentrated Load
32Dr. Abdulmannan Orabi IUST
Stress Due to a Concentrated Load
Boussinesq’s Formula for Point Loads
Joseph Valentin Boussinesq (13 March 1842 – 19 February
1929) was a French mathematician and physicist who made
significant contributions to the theory of hydrodynamics, vibration,
light, and heat.
33Dr. Abdulmannan Orabi IUST
Stresses in soil due to surface load
In 1885, Boussinesq developed the
mathematical relationships for determining
the normal and shear stresses at any point
inside a homogenous, elastic and isotropic
mediums due to a concentrated point loads
located at the surface
Vertical Stress in Soil
Stress Due to a Concentrated Load
34Dr. Abdulmannan Orabi IUST
The soil mass is elastic, isotropic (having
identical properties in all direction
throughout), homogeneous (identical elastic
properties) and semi-infinite depth.
The soil is weightless.
Stress Due to a Concentrated Load
Assumption:
35Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
The distribution of σz in the elastic medium
is apparently radially symmetrical.
The stress is infinite at the surface directly
beneath the point load and decreases with the
square of the depth.
Vertical Stress in Soil
Stress Due to a Concentrated Load
36Dr. Abdulmannan Orabi IUST
At any given non-zero radius, r, from the point
of load application, the vertical stress is zero
at the surface, increases to a maximum value at
a depth where , approximately, and
then decreases with depth.
E 39.25°
Vertical Stress in Soil
Stress Due to a Concentrated Load
37Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
According to Boussinesq’s analysis, the vertical stress
increase at point A caused by a point load of magnitude P
is given by
Stress Due to a Concentrated Load
D
∆
∆ M
∆ N
O
P
Q
.
P
D
1
38Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Stress Due to a Concentrated Load
According to Boussinesq’s analysis, the vertical stress
increase at point A caused by a point load of magnitude P
is given by
2 2 5/2
3 1
2 [1 ( / ) ]
z
P
z r z
σ
π
=
+
39Dr. Abdulmannan Orabi IUST
… … . 7 − 1
1
∆
.
Q
or
2z b
P
I
z
σ =
Equation shows that the vertical stress is
Directly proportional to the load
Inversely proportional to the depth squared, and
Proportional to some function of the ratio ( r/z).
Vertical Stress in Soil
Stress Due to a Concentrated Load
where
2 5/2
3 1
2 [1 ( / ) ]
bI
r zπ
=
+
40Dr. Abdulmannan Orabi IUST
… … … … . 7 − 2
It should be noted that the expression for z is
independent of elastic modulus (E) and
Poisson’s ratio (µ), i.e. stress increase with depth
is a function of geometry only.
Vertical Stress in Soil
Stress Due to a Concentrated Load
41Dr. Abdulmannan Orabi IUST
r/Z IB r/Z IB r/Z IB r/Z IB
0.00 0.4775 0.18 0.4409 0.36 0.3521 0.55 0.2466
0.01 0.4773 0.19 0.4370 0.37 0.3465 0.56 0.2414
0.02 0.477 0.20 0.4329 0.38 0.3408 0.57 0.2363
0.03 0.4764 0.21 0.4286 0.39 0.3351 0.58 0.2313
0.04 0.4756 0.22 0.4242 0.40 0.3294 0.59 0.2263
0.05 0.4745 0.23 0.4197 0.41 0.3238 0.60 0.2214
0.06 0.472 0.24 0.4151 0.42 0.3181 0.61 0.2165
0.07 0.4717 0.25 0.4103 0.43 0.3124 0.62 0.2117
0.08 0.4699 0.26 0.4054 0.44 0.3068 0.63 0.2070
0.09 0.4679 0.27 0.4004 0.45 0.3011 0.64 0.2024
0.1 0.4657 0.28 0.3954 0.46 0.2955 0.65 0.1978
0.11 0.4633 0.29 0.3902 0.47 0.2899 0.66 0.1934
0.12 0.4607 0.30 0.3849 0.48 0.2843 0.67 0.1889
0.13 0.4579 0.31 0.3796 0.49 0.2788 0.68 0.1846
0.14 0.4548 0.32 0.3742 0.50 0.2733 0.69 0.1804
0.15 0.4516 0.33 0.3687 0.51 0.2679 0.70 0.1762
0.16 0.4482 0.34 0.3632 0.52 0.2625 0.71 0.1721
0.17 0.4446 0.35 0.3577 0.53 0.2571 0.72 0.1681
0.54 0.2518 0.73 0.1641
Influence Factor Ib
42Dr. Abdulmannan Orabi IUST
r/Z IB r/Z IB r/Z IB r/Z IB
0.74 0.1603 0.94 0.0981 1.14 0.0595 1.34 0.0365
0.75 0.1565 0.95 0.0956 1.15 0.0581 1.35 0.0357
0.76 0.1527 0.96 0.0933 1.16 0.0567 1.36 0.0348
0.77 0.1491 0.97 0.0910 1.17 0.0553 1.37 0.0340
0.78 0.1455 0.98 0.0887 1.18 0.0539 1.38 0.0332
0.79 0.1420 0.99 0.0865 1.19 0.0526 1.39 0.0324
0.80 0.1386 1.0 0.0844 1.20 0.0513 1.40 0.0317
0.81 0.1353 1.01 0.0823 1.21 0.0501 1.41 0.0309
0.82 0.1320 1.02 0.0803 1.22 0.0489 1.42 0.0302
0.83 0.1288 1.03 0.0783 1.23 0.0477 1.43 0.0295
0.84 0.1257 1.04 0.0764 1.24 0.0466 1.44 0.0283
0.85 0.1226 1.05 0.0744 1.25 0.0454 1.45 0.0282
0.86 0.1196 1.06 0.0727 1.26 0.0443 1.46 0.0275
0.87 0.1166 1.07 0.0709 1.27 0.0433 1.47 0.0269
0.88 0.1138 1.08 0.0691 1.28 0.0422 1.48 0.0263
0.89 0.1110 1.09 0.0674 1.29 0.0412 1.49 0.0257
0.90 0.1083 1.10 0.0658 1.30 0.0402 1.50 0.0251
0.91 0.1057 1.11 0.0641 1.31 0.0393 1.51 0.0245
0.92 0.1031 1.12 0.0626 1.32 0.0384 1.52 0.0240
0.93 0.1005 1.13 0.0610 1.33 0.0374 1.53 0.0234
43Dr. Abdulmannan Orabi IUST
Influence Factor Ib
r/Z IB r/Z IB r/Z IB r/Z IB
1.54 0.0229 1.66 0.0175 1.86 0.0114 2.5 0.0034
1.55 0.0224 1.67 0.0171 1.88 0.0109 2.6 0.0029
1.56 0.0219 1.68 0.0167 1.90 0.0105 2.7 0.0024
1.57 0.0214 1.69 0.0163 1.92 0.0101 2.8 0.0021
1.58 0.0209 1.70 0.0160 1.94 0.0097 2.9 0.0017
1.59 0.0204 1.72 0.0153 1.96 0.0093 3.0 0.0015
1.60 0.0200 1.74 0.0147 1.98 0.0089 3.5 0.0007
1.61 0.0195 1.76 0.0141 2.0 0.0085 4.0 0.0004
1.62 0.0191 1.78 0.0135 2.1 0.0070 4.5 0.0002
1.63 0.0187 1.80 0.0129 2.2 0.0058 5.0 0.0001
1.64 0.0183 1.82 0.0124 2.3 0.0048
1.65 0.0179 1.84 0.0119 2.4 0.0040
44Dr. Abdulmannan Orabi IUST
Influence Factor Ib
Equation may be used to draw three types of pressure
distribution diagram. They are:
The vertical stress distribution on a horizontal
plane at depth of z below the ground surface
The vertical stress distribution on a vertical plane
at a distance of r from the load point, and
The stress isobar.
Vertical Stress in Soil
Pressure Distribution Diagram
45Dr. Abdulmannan Orabi IUST
The vertical stress distribution on a horizontal
plane at depth of z below the ground surface
U
5
5
Vertical Stress in Soil
Distribution on a horizontal plane
46Dr. Abdulmannan Orabi IUST
The vertical stress
distribution on a vertical
plane at a distance of r
from the point load
.
Vertical Stress in Soil
Distribution on a vertical plane O
47Dr. Abdulmannan Orabi IUST
U
Vertical Stress in Soil
Stress isobars
An isobar is a line which
connects all points of equal
stress below the ground
surface. In other words, an
isobar is a stress contour.
48Dr. Abdulmannan Orabi IUST
What is the vertical stress at point A of figure below
for the two loads, P1 and P2 ?
P1 = 350 kNP2 = 470 kN
Z=2.5m
2.3 m1.1 m
A
Worked Examples
Example 2
49Dr. Abdulmannan Orabi IUST
A four concentrated forces are located at corners of
a rectangular area with dimensions 8 m by 6 m as
shown in figure in the next slide. Compute the
vertical stress at points A and B, which are located
on the lines A – A’ , B – B’ at depth of 4 m below
the ground surface.
Worked Examples
Example 3
50Dr. Abdulmannan Orabi IUST
700 kN700 kN
700 kN700 kN
4 m
4 m
8 m
B
A’
A
B’
Worked Examples
Example 3
Dr. Abdulmannan Orabi IUST 51
Vertical Stress in Soil
Westergaard Formula
Westergaard proposed a formula for the
computation of vertical stress by a point load,
P at the surface as
O		+
2V + 	
.
/
In which µ is Poisson’s ratio
+ 1 − 2X /,2 − 2X-	
52Dr. Abdulmannan Orabi IUST
… . 7 − 3
Vertical Stress in Soil
Stress below a Line Load
The vertical stress increase due to line load , ,
inside the soil mass can be determined by using the
principles of the theory of elasticity, or
2	 	
V P
This equation can be rewritten as
/
2	
V 1
P
1P
P
53Dr. Abdulmannan Orabi IUST
… . 7 − 4
Vertical Stress in Soil
Vertical Stress caused by a horizontal line load
The vertical stress increase ( ) at point A in
the soil mass caused by a horizontal line load
can be given as :
2	 		P	
V P
1
	/ 	 	
P
54Dr. Abdulmannan Orabi IUST
… . 7 − 5
Vertical Stress in Soil
Vertical Stress caused by a strip load
The fundamental equation for the vertical stress
increase at a point in a soil mass as the result of
a line load can be used to determine the vertical
stress at a point caused by a flexible strip load of
width B.
The term strip loading will be used to indicate a
loading that has a finite width along the x axis
but an infinite length along the y axis.
55Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Vertical Stress caused by a strip load
α
β
6
B
Vertical stress at point A can be determined by equation:
[ sin cos( 2 )]o
z
q
σ α α α β
π
= + +
P
56Dr. Abdulmannan Orabi IUST
… . 7 − 6
B
[
0.25	
0.5	

]
^
0.5	
0.25	
Worked Examples
Example 4
Refer to figure below, The magnitude of the strip
load is 120 kPa. Calculate the vertical stress at
points, a , b, and c.
57Dr. Abdulmannan Orabi IUST
_
6
4
"
+
_
1 2 2[( )( ) ( )]o
z
q a b b
a a
σ α α α
π
+
= + −
Vertical Stress Due to Embankment Loading
The vertical stress increase in the soil mass due to
an embankment of height H may be expressed as
Vertical Stress in Soil
" 	)where:
	 	 	 `4+ a` 		
) 	 	 		 `4+ a`
58Dr. Abdulmannan Orabi IUST
… . 7 − 7
^ 7 6
2	`
120	aO+
3	`	
2	`
Refer to figure below. The magnitude of the load is
120 kPa. Calculate the vertical stress at points,
A , B, and C.
Worked Examples
Example 4
59Dr. Abdulmannan Orabi IUST
1- Under the center: The increase in the vertical
stress ( ) at depth z ( point A)under the center
of a circular area of diameter D = 2R carrying
a uniform pressure q is given by
Vertical Stress in Soil
Vertical Stress due to a uniformly loaded circular area
1 −
1
Q/ 1 /
60Dr. Abdulmannan Orabi IUST
… . 7 − 8
Vertical Stress in Soil
Vertical Stress due to a uniformly loaded circular area
6
6'
Q
6'
6
61Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
2- At any point: The increase in the vertical
stress ( ) at any point located at a depth z at
any distance r from the center of the loaded
area can be given
Vertical Stress due to a uniformly loaded circular area
where and are functions of z/R and r/R.
1' '
1' '
62Dr. Abdulmannan Orabi IUST
… . 7 − 9
Vertical Stress in Soil
Vertical Stress due to a uniformly loaded circular area
7
7'
.
Q
7
7'.
63Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Variation of with z/R and r/R.1'
64Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Variation of with z/R and r/R.1'
65Dr. Abdulmannan Orabi IUST
Variation of with z/R and r/R.'
Vertical Stress in Soil
66Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Variation of with z/R and r/R.'
67Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Vertical Stress Caused by a Rectangular loaded area
The increase in the vertical stress ( ) at depth z under a
corner of a rectangular area of dimensions B = m z and
L = n z carrying a uniform pressure q is given by:
z o zq Iσ =
c 3 	 +3 .	2 0 2 	 	 	.+ 	
d
	+ 2	

	
where :
68Dr. Abdulmannan Orabi IUST
… . 7 − 10
Vertical Stress in Soil
Vertical Stress Caused by a Rectangular loaded area
c
1
4V
2	`	 ` 1	
` ` 1
` 2
` 1
+ e
2	`	 ` 1
` − ` 1
The influence factor
can be expressed as
`
d
			+ 2	

where :
69Dr. Abdulmannan Orabi IUST
… . 7 − 11
The increase in the stress at any point below a
rectangular loaded area can be found by dividing
the area into four rectangles. The point A’ is the
corner common to all four rectangles.
Vertical Stress in Soil
Vertical Stress Caused by a Rectangular loaded area
1 2
34
6'
* f
g c g
70Dr. Abdulmannan Orabi IUST
Vertical Stress in Soil
Vertical Stress Caused by a Rectangular loaded area
71Dr. Abdulmannan Orabi IUST
4
6'
6'
6'
6'
	−		h5
		h5i	−		h5
+ h5 h5
4 3
4
2
9
1
1 2
3
5
5
1
8
7 9
87
4
7
3
* − − f
Variation of with m and nc
n
m
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0.1 0.0047 0.0092 0.0132 0.0168 0.0198 0.0222 0.0242 0.0258
0.2 0.0092 0.0179 0.0259 0.0328 0.0387 0.0435 0.0474 0.0504
0.3 0.0132 0.0259 0.0374 0.0474 0.0559 0.0629 0.0686 0.0731
0.4 0.0168 0.0328 0.0474 0.0602 0.0711 0.0801 0.0873 0.0931
0.5 0.0198 0.0387 0.0559 0.0711 0.0840 0.0947 0.1034 0.1104
0.6 0.0222 0.0435 0.0629 0.0801 0.0947 0.1069 0.1168 0.1247
0.7 0.0242 0.0474 0.0686 0.0873 0.1034 0.1169 0.1277 0.1365
0.8 0.0258 0.0504 0.0731 0.0931 0.1104 0.1247 0.1365 0.1461
0.9 0.0270 0.0528 0.0766 0.0977 0.1158 0.1311 0.1436 0.1537
1.0 0.0279 0.0547 0.0794 0.1013 0.1202 0.1361 0.1491 0.1598
72Dr. Abdulmannan Orabi IUST
Variation of with m and nc
n
m
0.9 1 1.2 1.4 1.6 1.8 2.0 2.5
0.1 0.0270 0.0279 0.0293 0.0301 0.0306 0.0309 0.0311 0.0314
0.2 0.0528 0.0547 0.0573 0.0589 0.0599 0.0606 0.0610 0.0616
0.3 0.0766 0.0794 0.0832 0.0856 0.0871 0.0880 0.0887 0.0895
0.4 0.0977 0.1013 0.1063 0.1094 0.1114 0.1126 0.1134 0.1145
0.5 0.1158 0.1202 0.1263 0.1300 0.1324 0.1340 0.1350 0.1363
0.6 0.1311 0.1361 0.1431 0.1475 0.1503 0.1521 0.1533 0.1548
0.7 0.1436 0.1491 0.1570 0.1620 0.1652 0.1672 0.1686 0.1704
0.8 0.1537 0.1598 0.1684 0.1739 0.1774 0.1797 0.1812 0.1832
0.9 0.1619 0.1684 0.1777 0.1836 0.1875 0.1899 0.1915 0.1938
1.0 0.1684 0.1752 0.1851 0.1914 0.1955 0.1981 0.1999 0.2024
73Dr. Abdulmannan Orabi IUST
Variation of with m and nc
n
m
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
1.2 0.0293 0.0573 0.0832 0.1063 0.1263 0.1431 0.1570 0.1684
1.4 0.0301 0.0589 0.0856 0.1094 0.1300 0.1475 0.1620 0.1739
1.6 0.0306 0.0599 0.0871 0.1114 0.1324 0.1503 0.1652 0.1774
1.8 0.0309 0.0606 0.0880 0.1126 0.1340 0.1521 0.1672 0.1797
2.0 0.0311 0.0610 0.0887 0.1134 0.1350 0.1533 0.1686 0.1812
2.5 0.0314 0.0616 0.0895 0.1145 0.1363 0.1548 0.1704 0.1832
3.0 0.0315 0.0618 0.0898 0.1150 0.1368 0.1555 0.1711 0.1841
4.0 0.0316 0.0619 0.0901 0.1153 0.1372 0.1560 0.1717 0.1847
5.0 0.0316 0.0620 0.0901 0.1154 0.1374 0.1561 0.1719 0.1849
6.0 0.0316 0.0620 0.0902 0.1154 0.1374 0.1562 0.1719 0.1850
74Dr. Abdulmannan Orabi IUST
Variation of with m and nc
n
m
0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.5
1.2 0.1777 0.1851 0.1958 0.2028 0.2073 0.2103 0.2124 0.2151
1.4 0.1836 0.1914 0.2028 0.2102 0.2151 0.2184 0.2206 0.2236
1.6 0.1874 0.1955 0.2073 0.2151 0.2203 0.2237 0.2261 0.2294
1.8 0.1899 0.1981 0.2103 0.2183 0.2237 0.2274 0.2299 0.2333
2.0 0.1915 0.1999 0.2124 0.2206 0.2261 0.2299 0.2325 0.2361
2.5 0.1938 0.2024 0.2151 0.2236 0.2294 0.2333 0.2361 0.2401
3.0 0.1947 0.2034 0.2163 0.2250 0.2309 0.2350 0.2378 0.2420
4.0 0.1954 0.2042 0.2172 0.2260 0.2320 0.2362 0.2391 0.2434
5.0 0.1956 0.2044 0.2175 0.2263 0.2324 0.2366 0.2395 0.2439
6.0 0.1957 0.2045 0.2176 0.2264 0.2325 0.2367 0.2397 0.2441
75Dr. Abdulmannan Orabi IUST
Approximate Method
B
B + z
2
1
z
"
O
76Dr. Abdulmannan Orabi IUST
2V:1H method
A simple but approximate method is sometimes used for
calculating the stress change at various depths as a
result of the application of a pressure at the ground
surface.
The transmission of stress is
assumed to follow outward
fanning lines at a slope of 1
horizontal to 2 vertical.
Approximate Method
For uniform footing (B x L) we can estimate the
change in vertical stress with depth using the Boston
Rule. Assumes stress at depth is constant below
foundation influence area
B
B + z
2
1
z
"	d		
,d -	, -	
"
O
"
O		
d 		
77Dr. Abdulmannan Orabi IUST
… . 7 − 12
2V:1H method
Approximate Method
B + z
L
B
z
Stress on this plane "
j
d ∗ 	
Stress on this plane at depth z,
"	d		
,d -	, -	
Rectangular footing
B
B + z
2
1
78Dr. Abdulmannan Orabi IUST
2V:1H method
Newmark Method
79Dr. Abdulmannan Orabi IUST
• Stresses due to foundation loads of arbitrary
shape applied at the ground surface
• Newmark’s chart provides a graphical
method for calculating the stress increase due
to a uniformly loaded region, of arbitrary
shape resting on a deep homogeneous
isotropic elastic region.
Newmark Method
• The Newmark’s Influence Chart method
consists of concentric circles drawn to scale,
each square contributes a fraction of the
stress.
• In most charts each square contributes
1/200 (or 0.005) units of stress. (influence
value, I)
80Dr. Abdulmannan Orabi IUST
Newmark Method
81Dr. Abdulmannan Orabi IUST
The use of the chart is
based on a factor
termed the influence
value, determined from
the number of units
into which the chart is
subdivided.
Influence value 0.005
A
B
1 unit
Newmark Method
A B Influence
value = 0.005
Total number of block on chart = 200 and influence
value = 1/200
The influence chart may be used to compute
the pressure on an element of soil beneath a
footing, or from pattern of footings, and for
any depth z below the footing. It is only
necessary to draw the footing pattern to a
scale of z = length AB of the chart. (If z=
6m and AB = 30mm, the scale is 1/200).
Newmark Method
83Dr. Abdulmannan Orabi IUST
The footing plan will be placed on the influence
chart with the point for which the stress is desired at
the center of the circles.
Newmark Method
The units (segments or partial segments) enclosed
by the footing are counted, and the increase in
stress at the depth z is computed as
"	c	j	
Where I	is	the	influence	factor		of	the	chart.
" +00 2	0. . 	 	 	+. + 	 2+ 	3 +3 	0. . 	 	
j `4 .	 	 	3 2	,	0+. + 	 	+. 	 `+ 2-
84Dr. Abdulmannan Orabi IUST
… . 7 − 13
Newmark Method
85Dr. Abdulmannan Orabi IUST
Stress Distribution

More Related Content

What's hot

Bearing capacity of shallow foundations by abhishek sharma
Bearing capacity of shallow foundations by abhishek sharma Bearing capacity of shallow foundations by abhishek sharma
Bearing capacity of shallow foundations by abhishek sharma ABHISHEK SHARMA
 
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]Muhammad Irfan
 
Class 7 Consolidation Test ( Geotechnical Engineering )
Class 7    Consolidation Test ( Geotechnical Engineering )Class 7    Consolidation Test ( Geotechnical Engineering )
Class 7 Consolidation Test ( Geotechnical Engineering )Hossam Shafiq I
 
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]Muhammad Irfan
 
Lateral Earth Pressure
Lateral Earth PressureLateral Earth Pressure
Lateral Earth PressureFast-NU Lahore
 
Problems on bearing capacity of soil
Problems on bearing capacity of soilProblems on bearing capacity of soil
Problems on bearing capacity of soilLatif Hyder Wadho
 
Determination of Immediate Settlement
Determination of Immediate Settlement Determination of Immediate Settlement
Determination of Immediate Settlement Suez Halder
 
Geotechnical Engineering-I [Lec #9: Atterberg limits]
Geotechnical Engineering-I [Lec #9: Atterberg limits]Geotechnical Engineering-I [Lec #9: Atterberg limits]
Geotechnical Engineering-I [Lec #9: Atterberg limits]Muhammad Irfan
 
Case study on effect of water table on bearing capacity
Case study on effect of water table on bearing capacityCase study on effect of water table on bearing capacity
Case study on effect of water table on bearing capacityAbhishek Mangukiya
 
TERZAGHI’S BEARING CAPACITY THEORY
TERZAGHI’S BEARING CAPACITY THEORYTERZAGHI’S BEARING CAPACITY THEORY
TERZAGHI’S BEARING CAPACITY THEORYSANJEEV Wazir
 
Consolidation settlement
Consolidation settlementConsolidation settlement
Consolidation settlementParth Joshi
 
Problems on piles and deep footing
Problems on piles and deep footingProblems on piles and deep footing
Problems on piles and deep footingLatif Hyder Wadho
 
ppt of consolidation and settlement of soil
ppt of consolidation and settlement of soilppt of consolidation and settlement of soil
ppt of consolidation and settlement of soilSAMRAT CHODHURY
 
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]Geotechnical Engineering-I [Lec #24: Soil Permeability - II]
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]Muhammad Irfan
 
Shear Strength of Soil
Shear Strength of SoilShear Strength of Soil
Shear Strength of SoilUmang Parmar
 
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]Muhammad Irfan
 

What's hot (20)

Bearing capacity of shallow foundations by abhishek sharma
Bearing capacity of shallow foundations by abhishek sharma Bearing capacity of shallow foundations by abhishek sharma
Bearing capacity of shallow foundations by abhishek sharma
 
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]
Geotechnical Engineering-II [Lec #19: General Bearing Capacity Equation]
 
Class 7 Consolidation Test ( Geotechnical Engineering )
Class 7    Consolidation Test ( Geotechnical Engineering )Class 7    Consolidation Test ( Geotechnical Engineering )
Class 7 Consolidation Test ( Geotechnical Engineering )
 
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]
Geotechnical Engineering-II [Lec #9+10: Westergaard Theory]
 
Lateral Earth Pressure
Lateral Earth PressureLateral Earth Pressure
Lateral Earth Pressure
 
Problems on bearing capacity of soil
Problems on bearing capacity of soilProblems on bearing capacity of soil
Problems on bearing capacity of soil
 
Determination of Immediate Settlement
Determination of Immediate Settlement Determination of Immediate Settlement
Determination of Immediate Settlement
 
Geotechnical Engineering-I [Lec #9: Atterberg limits]
Geotechnical Engineering-I [Lec #9: Atterberg limits]Geotechnical Engineering-I [Lec #9: Atterberg limits]
Geotechnical Engineering-I [Lec #9: Atterberg limits]
 
Lecture 2 bearing capacity
Lecture 2 bearing capacityLecture 2 bearing capacity
Lecture 2 bearing capacity
 
Boussinesq'S theory
Boussinesq'S theoryBoussinesq'S theory
Boussinesq'S theory
 
05 chapter 6 mat foundations
05 chapter 6 mat foundations05 chapter 6 mat foundations
05 chapter 6 mat foundations
 
Case study on effect of water table on bearing capacity
Case study on effect of water table on bearing capacityCase study on effect of water table on bearing capacity
Case study on effect of water table on bearing capacity
 
TERZAGHI’S BEARING CAPACITY THEORY
TERZAGHI’S BEARING CAPACITY THEORYTERZAGHI’S BEARING CAPACITY THEORY
TERZAGHI’S BEARING CAPACITY THEORY
 
Consolidation settlement
Consolidation settlementConsolidation settlement
Consolidation settlement
 
Problems on piles and deep footing
Problems on piles and deep footingProblems on piles and deep footing
Problems on piles and deep footing
 
ppt of consolidation and settlement of soil
ppt of consolidation and settlement of soilppt of consolidation and settlement of soil
ppt of consolidation and settlement of soil
 
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]Geotechnical Engineering-I [Lec #24: Soil Permeability - II]
Geotechnical Engineering-I [Lec #24: Soil Permeability - II]
 
Shear Strength of Soil
Shear Strength of SoilShear Strength of Soil
Shear Strength of Soil
 
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]
Geotechnical Engineering-II [Lec #23: Rankine Earth Pressure Theory]
 
Lecture 4 classification of soil
Lecture 4 classification of soilLecture 4 classification of soil
Lecture 4 classification of soil
 

Viewers also liked

Lecture 1 introduction & properties of soil
Lecture 1  introduction & properties of soilLecture 1  introduction & properties of soil
Lecture 1 introduction & properties of soilDr.Abdulmannan Orabi
 
Lecture 1 introduction & types of foundation
Lecture 1  introduction & types of foundationLecture 1  introduction & types of foundation
Lecture 1 introduction & types of foundationDr.Abdulmannan Orabi
 
Lead soil field test presentation
Lead soil field test presentation Lead soil field test presentation
Lead soil field test presentation ITS (Sensafe)
 
Structural engineering ppt 1
Structural  engineering ppt 1Structural  engineering ppt 1
Structural engineering ppt 1lavanya prabha
 
Chapter 3 classification
Chapter 3 classificationChapter 3 classification
Chapter 3 classificationGokul Saud
 
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...Jagmohan Garg
 
Diagrid structure system - شبكات العقد الاطارية
Diagrid structure system -    شبكات العقد الاطاريةDiagrid structure system -    شبكات العقد الاطارية
Diagrid structure system - شبكات العقد الاطاريةDr.Youssef Hammida
 
Runoff and Hydrograph
Runoff and HydrographRunoff and Hydrograph
Runoff and HydrographSajjad Ahmad
 

Viewers also liked (20)

Lecture 2 grain size distribution
Lecture 2 grain size distributionLecture 2 grain size distribution
Lecture 2 grain size distribution
 
Lecture 3 consistncy of soil
Lecture 3 consistncy of soilLecture 3 consistncy of soil
Lecture 3 consistncy of soil
 
Lecture 1 introduction & properties of soil
Lecture 1  introduction & properties of soilLecture 1  introduction & properties of soil
Lecture 1 introduction & properties of soil
 
Lecture 5 soil compaction
Lecture 5 soil compactionLecture 5 soil compaction
Lecture 5 soil compaction
 
Lecture 6 soil permeability
Lecture 6 soil permeabilityLecture 6 soil permeability
Lecture 6 soil permeability
 
Lecture 7 strap footing
Lecture 7  strap  footingLecture 7  strap  footing
Lecture 7 strap footing
 
Lecture 1 introduction & types of foundation
Lecture 1  introduction & types of foundationLecture 1  introduction & types of foundation
Lecture 1 introduction & types of foundation
 
Lecture 8 raft foundation
Lecture 8 raft foundationLecture 8 raft foundation
Lecture 8 raft foundation
 
5 effective stress concept
5  effective stress concept5  effective stress concept
5 effective stress concept
 
6 stresses in soil mass
6  stresses in soil mass6  stresses in soil mass
6 stresses in soil mass
 
Lead soil field test presentation
Lead soil field test presentation Lead soil field test presentation
Lead soil field test presentation
 
Structural engineering ppt 1
Structural  engineering ppt 1Structural  engineering ppt 1
Structural engineering ppt 1
 
Chapter 3 classification
Chapter 3 classificationChapter 3 classification
Chapter 3 classification
 
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...
 
Diagrid structure system - شبكات العقد الاطارية
Diagrid structure system -    شبكات العقد الاطاريةDiagrid structure system -    شبكات العقد الاطارية
Diagrid structure system - شبكات العقد الاطارية
 
Runoff and Hydrograph
Runoff and HydrographRunoff and Hydrograph
Runoff and Hydrograph
 
Earth pressure
Earth pressureEarth pressure
Earth pressure
 
CE-235 EH Lec 3
CE-235 EH Lec 3CE-235 EH Lec 3
CE-235 EH Lec 3
 
ce235-eh-lec-2
ce235-eh-lec-2ce235-eh-lec-2
ce235-eh-lec-2
 
Flood routing
Flood routingFlood routing
Flood routing
 

Similar to Stress Distribution

lecture7stressdistributioninsoil-161122164340.pdf
lecture7stressdistributioninsoil-161122164340.pdflecture7stressdistributioninsoil-161122164340.pdf
lecture7stressdistributioninsoil-161122164340.pdfADENIRANfirdaus
 
Lecture 3 stresses in soil mass
Lecture 3 stresses in soil massLecture 3 stresses in soil mass
Lecture 3 stresses in soil massELIASASSEFA3
 
Lecture 3 stresses in soil mass
Lecture 3 stresses in soil massLecture 3 stresses in soil mass
Lecture 3 stresses in soil massELIASASSEFA3
 
326027186-Stresses-in-Soil.pdf
326027186-Stresses-in-Soil.pdf326027186-Stresses-in-Soil.pdf
326027186-Stresses-in-Soil.pdfBrianMutethia
 
Section 2-gte-i
Section  2-gte-iSection  2-gte-i
Section 2-gte-iDYPCET
 
Ge i-module2-rajesh sir
Ge i-module2-rajesh sirGe i-module2-rajesh sir
Ge i-module2-rajesh sirSHAMJITH KM
 
Lecture5soilcompaction 161028162415
Lecture5soilcompaction 161028162415Lecture5soilcompaction 161028162415
Lecture5soilcompaction 161028162415Bahir dar university
 
Stress distribution of the soil
Stress distribution of the soilStress distribution of the soil
Stress distribution of the soilDharmik Navadiya
 
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.ppt
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.pptUNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.ppt
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.pptyarlagaddanagalakshm
 
EARTH PRESSURE - REVISED for backlog.pptx
EARTH PRESSURE - REVISED for backlog.pptxEARTH PRESSURE - REVISED for backlog.pptx
EARTH PRESSURE - REVISED for backlog.pptxathars248
 
lecture5soilcompaction-161028162415.pptx
lecture5soilcompaction-161028162415.pptxlecture5soilcompaction-161028162415.pptx
lecture5soilcompaction-161028162415.pptxDine41
 
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]Muhammad Irfan
 
©McGraw-Hill Education. All rights reserved. Authorized only f.docx
©McGraw-Hill Education. All rights reserved. Authorized only f.docx©McGraw-Hill Education. All rights reserved. Authorized only f.docx
©McGraw-Hill Education. All rights reserved. Authorized only f.docxgerardkortney
 
SOIL STRENGTH AND SOIL FORCES
SOIL STRENGTH AND SOIL FORCESSOIL STRENGTH AND SOIL FORCES
SOIL STRENGTH AND SOIL FORCESAfendiAriff
 

Similar to Stress Distribution (20)

lecture7stressdistributioninsoil-161122164340.pdf
lecture7stressdistributioninsoil-161122164340.pdflecture7stressdistributioninsoil-161122164340.pdf
lecture7stressdistributioninsoil-161122164340.pdf
 
Lecture 3 stresses in soil mass
Lecture 3 stresses in soil massLecture 3 stresses in soil mass
Lecture 3 stresses in soil mass
 
Lecture 3 stresses in soil mass
Lecture 3 stresses in soil massLecture 3 stresses in soil mass
Lecture 3 stresses in soil mass
 
326027186-Stresses-in-Soil.pdf
326027186-Stresses-in-Soil.pdf326027186-Stresses-in-Soil.pdf
326027186-Stresses-in-Soil.pdf
 
Section 2-gte-i
Section  2-gte-iSection  2-gte-i
Section 2-gte-i
 
Ge i-module2-rajesh sir
Ge i-module2-rajesh sirGe i-module2-rajesh sir
Ge i-module2-rajesh sir
 
Lecture5soilcompaction 161028162415
Lecture5soilcompaction 161028162415Lecture5soilcompaction 161028162415
Lecture5soilcompaction 161028162415
 
Stress distribution of the soil
Stress distribution of the soilStress distribution of the soil
Stress distribution of the soil
 
SHEAR STRENGTH THEORY
SHEAR STRENGTH THEORYSHEAR STRENGTH THEORY
SHEAR STRENGTH THEORY
 
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.ppt
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.pptUNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.ppt
UNIT-1 SOIL MECHANICS_Y. NAGA LAKSHMI.ppt
 
EARTH PRESSURE - REVISED for backlog.pptx
EARTH PRESSURE - REVISED for backlog.pptxEARTH PRESSURE - REVISED for backlog.pptx
EARTH PRESSURE - REVISED for backlog.pptx
 
Chapter 05
Chapter 05Chapter 05
Chapter 05
 
lecture5soilcompaction-161028162415.pptx
lecture5soilcompaction-161028162415.pptxlecture5soilcompaction-161028162415.pptx
lecture5soilcompaction-161028162415.pptx
 
10 fluid dynamics
10 fluid dynamics10 fluid dynamics
10 fluid dynamics
 
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]
Geotechnical Engineering-II [Lec #7: Soil Stresses due to External Load]
 
Effective stress
Effective stressEffective stress
Effective stress
 
©McGraw-Hill Education. All rights reserved. Authorized only f.docx
©McGraw-Hill Education. All rights reserved. Authorized only f.docx©McGraw-Hill Education. All rights reserved. Authorized only f.docx
©McGraw-Hill Education. All rights reserved. Authorized only f.docx
 
Sm Chapter VII
Sm Chapter VIISm Chapter VII
Sm Chapter VII
 
Ly thuyet ALD_Geo 5.pdf
Ly thuyet ALD_Geo 5.pdfLy thuyet ALD_Geo 5.pdf
Ly thuyet ALD_Geo 5.pdf
 
SOIL STRENGTH AND SOIL FORCES
SOIL STRENGTH AND SOIL FORCESSOIL STRENGTH AND SOIL FORCES
SOIL STRENGTH AND SOIL FORCES
 

Recently uploaded

UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)
UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)
UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)Dr SOUNDIRARAJ N
 
Work Experience-Dalton Park.pptxfvvvvvvv
Work Experience-Dalton Park.pptxfvvvvvvvWork Experience-Dalton Park.pptxfvvvvvvv
Work Experience-Dalton Park.pptxfvvvvvvvLewisJB
 
8251 universal synchronous asynchronous receiver transmitter
8251 universal synchronous asynchronous receiver transmitter8251 universal synchronous asynchronous receiver transmitter
8251 universal synchronous asynchronous receiver transmitterShivangiSharma879191
 
An experimental study in using natural admixture as an alternative for chemic...
An experimental study in using natural admixture as an alternative for chemic...An experimental study in using natural admixture as an alternative for chemic...
An experimental study in using natural admixture as an alternative for chemic...Chandu841456
 
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catchers
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor CatchersTechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catchers
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catcherssdickerson1
 
Class 1 | NFPA 72 | Overview Fire Alarm System
Class 1 | NFPA 72 | Overview Fire Alarm SystemClass 1 | NFPA 72 | Overview Fire Alarm System
Class 1 | NFPA 72 | Overview Fire Alarm Systemirfanmechengr
 
lifi-technology with integration of IOT.pptx
lifi-technology with integration of IOT.pptxlifi-technology with integration of IOT.pptx
lifi-technology with integration of IOT.pptxsomshekarkn64
 
IVE Industry Focused Event - Defence Sector 2024
IVE Industry Focused Event - Defence Sector 2024IVE Industry Focused Event - Defence Sector 2024
IVE Industry Focused Event - Defence Sector 2024Mark Billinghurst
 
Vishratwadi & Ghorpadi Bridge Tender documents
Vishratwadi & Ghorpadi Bridge Tender documentsVishratwadi & Ghorpadi Bridge Tender documents
Vishratwadi & Ghorpadi Bridge Tender documentsSachinPawar510423
 
Solving The Right Triangles PowerPoint 2.ppt
Solving The Right Triangles PowerPoint 2.pptSolving The Right Triangles PowerPoint 2.ppt
Solving The Right Triangles PowerPoint 2.pptJasonTagapanGulla
 
Call Girls Delhi {Jodhpur} 9711199012 high profile service
Call Girls Delhi {Jodhpur} 9711199012 high profile serviceCall Girls Delhi {Jodhpur} 9711199012 high profile service
Call Girls Delhi {Jodhpur} 9711199012 high profile servicerehmti665
 
Sachpazis Costas: Geotechnical Engineering: A student's Perspective Introduction
Sachpazis Costas: Geotechnical Engineering: A student's Perspective IntroductionSachpazis Costas: Geotechnical Engineering: A student's Perspective Introduction
Sachpazis Costas: Geotechnical Engineering: A student's Perspective IntroductionDr.Costas Sachpazis
 
Indian Dairy Industry Present Status and.ppt
Indian Dairy Industry Present Status and.pptIndian Dairy Industry Present Status and.ppt
Indian Dairy Industry Present Status and.pptMadan Karki
 
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfg
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfgUnit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfg
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfgsaravananr517913
 
Piping Basic stress analysis by engineering
Piping Basic stress analysis by engineeringPiping Basic stress analysis by engineering
Piping Basic stress analysis by engineeringJuanCarlosMorales19600
 
Risk Assessment For Installation of Drainage Pipes.pdf
Risk Assessment For Installation of Drainage Pipes.pdfRisk Assessment For Installation of Drainage Pipes.pdf
Risk Assessment For Installation of Drainage Pipes.pdfROCENODodongVILLACER
 
Introduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHIntroduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHC Sai Kiran
 

Recently uploaded (20)

UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)
UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)
UNIT III ANALOG ELECTRONICS (BASIC ELECTRONICS)
 
Work Experience-Dalton Park.pptxfvvvvvvv
Work Experience-Dalton Park.pptxfvvvvvvvWork Experience-Dalton Park.pptxfvvvvvvv
Work Experience-Dalton Park.pptxfvvvvvvv
 
8251 universal synchronous asynchronous receiver transmitter
8251 universal synchronous asynchronous receiver transmitter8251 universal synchronous asynchronous receiver transmitter
8251 universal synchronous asynchronous receiver transmitter
 
An experimental study in using natural admixture as an alternative for chemic...
An experimental study in using natural admixture as an alternative for chemic...An experimental study in using natural admixture as an alternative for chemic...
An experimental study in using natural admixture as an alternative for chemic...
 
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catchers
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor CatchersTechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catchers
TechTAC® CFD Report Summary: A Comparison of Two Types of Tubing Anchor Catchers
 
Class 1 | NFPA 72 | Overview Fire Alarm System
Class 1 | NFPA 72 | Overview Fire Alarm SystemClass 1 | NFPA 72 | Overview Fire Alarm System
Class 1 | NFPA 72 | Overview Fire Alarm System
 
lifi-technology with integration of IOT.pptx
lifi-technology with integration of IOT.pptxlifi-technology with integration of IOT.pptx
lifi-technology with integration of IOT.pptx
 
IVE Industry Focused Event - Defence Sector 2024
IVE Industry Focused Event - Defence Sector 2024IVE Industry Focused Event - Defence Sector 2024
IVE Industry Focused Event - Defence Sector 2024
 
Vishratwadi & Ghorpadi Bridge Tender documents
Vishratwadi & Ghorpadi Bridge Tender documentsVishratwadi & Ghorpadi Bridge Tender documents
Vishratwadi & Ghorpadi Bridge Tender documents
 
Solving The Right Triangles PowerPoint 2.ppt
Solving The Right Triangles PowerPoint 2.pptSolving The Right Triangles PowerPoint 2.ppt
Solving The Right Triangles PowerPoint 2.ppt
 
Call Girls Delhi {Jodhpur} 9711199012 high profile service
Call Girls Delhi {Jodhpur} 9711199012 high profile serviceCall Girls Delhi {Jodhpur} 9711199012 high profile service
Call Girls Delhi {Jodhpur} 9711199012 high profile service
 
Sachpazis Costas: Geotechnical Engineering: A student's Perspective Introduction
Sachpazis Costas: Geotechnical Engineering: A student's Perspective IntroductionSachpazis Costas: Geotechnical Engineering: A student's Perspective Introduction
Sachpazis Costas: Geotechnical Engineering: A student's Perspective Introduction
 
9953056974 Call Girls In South Ex, Escorts (Delhi) NCR.pdf
9953056974 Call Girls In South Ex, Escorts (Delhi) NCR.pdf9953056974 Call Girls In South Ex, Escorts (Delhi) NCR.pdf
9953056974 Call Girls In South Ex, Escorts (Delhi) NCR.pdf
 
Indian Dairy Industry Present Status and.ppt
Indian Dairy Industry Present Status and.pptIndian Dairy Industry Present Status and.ppt
Indian Dairy Industry Present Status and.ppt
 
🔝9953056974🔝!!-YOUNG call girls in Rajendra Nagar Escort rvice Shot 2000 nigh...
🔝9953056974🔝!!-YOUNG call girls in Rajendra Nagar Escort rvice Shot 2000 nigh...🔝9953056974🔝!!-YOUNG call girls in Rajendra Nagar Escort rvice Shot 2000 nigh...
🔝9953056974🔝!!-YOUNG call girls in Rajendra Nagar Escort rvice Shot 2000 nigh...
 
young call girls in Green Park🔝 9953056974 🔝 escort Service
young call girls in Green Park🔝 9953056974 🔝 escort Serviceyoung call girls in Green Park🔝 9953056974 🔝 escort Service
young call girls in Green Park🔝 9953056974 🔝 escort Service
 
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfg
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfgUnit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfg
Unit7-DC_Motors nkkjnsdkfnfcdfknfdgfggfg
 
Piping Basic stress analysis by engineering
Piping Basic stress analysis by engineeringPiping Basic stress analysis by engineering
Piping Basic stress analysis by engineering
 
Risk Assessment For Installation of Drainage Pipes.pdf
Risk Assessment For Installation of Drainage Pipes.pdfRisk Assessment For Installation of Drainage Pipes.pdf
Risk Assessment For Installation of Drainage Pipes.pdf
 
Introduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHIntroduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECH
 

Stress Distribution

  • 1. INTERNATIONAL UNIVERSITY FOR SCIENCE & TECHNOLOGY ‫وا‬ ‫م‬ ‫ا‬ ‫و‬ ‫ا‬ ‫ا‬ CIVIL ENGINEERING AND ENVIRONMENTAL DEPARTMENT 303322 - Soil Mechanics Stress Distribution in Soil Dr. Abdulmannan Orabi Lecture 2 Lecture 7
  • 2. Dr. Abdulmannan Orabi IUST 2 Das, B., M. (2014), “ Principles of geotechnical Engineering ” Eighth Edition, CENGAGE Learning, ISBN-13: 978-0-495-41130-7. Knappett, J. A. and Craig R. F. (2012), “ Craig’s Soil Mechanics” Eighth Edition, Spon Press, ISBN: 978- 0-415-56125-9. References
  • 3. Stress in soil due to self weight Stress Distribution in Soil Stress in soil due to surface load 3Dr. Abdulmannan Orabi IUST
  • 4. Stress due to self weight The vertical stress on element A can be determined simply from the mass of the overlying material. If represents the unit weight of the soil, the vertical stress is Variation of stresses with depth A Ground surface zz ⋅= γσ 4Dr. Abdulmannan Orabi IUST
  • 5. ∑= ⋅=⋅++⋅+⋅= n i iinnz hhhh 1 2211 ...... γγγγσ Stress due to self weight Stresses in a Layered Deposit The stresses in a deposit consisting of layers of soil having different densities may be determined as Vertical stress at depth z1 Vertical stress at depth z2 Vertical stress at depth z3 ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ 5Dr. Abdulmannan Orabi IUST
  • 6. With uniform surcharge on infinite land surface Stress due to self weight Original land surface Conversion land surface ∗ 6Dr. Abdulmannan Orabi IUST
  • 7. Stress due to self weight ∗ Vertical stresses due to self weight increase with depth, There are 3 types of geostatic stresses: a. Total Stress, σtotal b. Effective Stress, σ' c. Pore Water Pressure, u Vertical Stresses 7Dr. Abdulmannan Orabi IUST
  • 8. Stress due to self weight Consider a soil mass having a horizontal surface and with the water table at surface level. The total vertical stress at depth z is equal to the weight of all material (solids + water) per unit area above that depth ,i.e Total vertical stress !"!#$ %#! ∗ 8Dr. Abdulmannan Orabi IUST
  • 9. Stress due to self weight The pore water pressure at any depth will be hydrostatic since the void space between the solid particles is continuous, therefore at depth z: Pore water pressure & ∗ If the pores of a soil mass are filled with water and if a pressure induced into the pore water, tries to separate the grains, this pressure is termed as pore water pressure 9Dr. Abdulmannan Orabi IUST
  • 10. Stress due to self weight Effective vertical stress due to self weight of soil The difference between the total stress ( !"!#$) and the pore pressure (u) in a saturated soil has been defined by Terzaghi as the effective stress ( ).' ' !"!#$ − The pressure transmitted through grain to grain at the contact points through a soil mass is termed as effective pressure. 10Dr. Abdulmannan Orabi IUST
  • 11. Stress due to self weight Stresses in Saturated Soil If water is seeping, the effective stress at any point in a soil mass will differ from that in the static case. It will increase or decrease, depending on the direction of seepage. The increasing in effective pressure due to the flow of water through the pores of the soil is known as seepage pressure. 11Dr. Abdulmannan Orabi IUST
  • 12. A column of saturated soil mass with no seepage of water in any direction. The total stress at the elevation of point A can be obtained from the saturated unit weight of the soil and the unit weight of water above it. Thus, Stress due to self weight Stresses in Saturated Soil without Seepage 0 A Solid particle Pore water )* )& + + 12Dr. Abdulmannan Orabi IUST
  • 13. 0 A Solid particle Pore water )* )& + + + + Forces acting at the points of contact of soil particles at the level of point A Stress due to self weight Stresses in Saturated Soil without Seepage & ) ,)* − )- %#! where + . + /+ 0 1 %#! + .+ 2 )* 2 + 3 4 0 1 + 2 + . +4 13Dr. Abdulmannan Orabi IUST
  • 14. Stress due to self weight Stresses in Saturated Soil without Seepage ) ) 5 6 7 8 Valve (closed) Stress at point A, • Total stress: • Pore water pressure: • Effective stress: * & ) * & ) * ' * − * 0 Stress at point B, • Total stress: • Pore water pressure • Effective stress: : & ) ) ∗ %#! : ,) ) - & : ' : − : : ' ) %;< 14Dr. Abdulmannan Orabi IUST
  • 15. Stress due to self weight Stresses in Saturated Soil without Seepage Stress at point C, • Total stress: = & ) ∗ %#! > ,) - & > ' > − > > ' %;< • Pore water pressure: • Effective stress: Total stress Pore water Pressure, u Effective stress DepthDepth Depth 15Dr. Abdulmannan Orabi IUST
  • 16. ) ) 5 6 7 8 Valve (open) ? ( @ AB - Stress due to self weight Stresses in Saturated Soil with Upward Seepage Stress at point A, • Total stress: • Pore water pressure: • Effective stress: * & ) * & ) * ' * − * 0 16Dr. Abdulmannan Orabi IUST
  • 17. Stresses in Saturated Soil with Upward Seepage Stress due to self weight Stress at point B, • Total stress: • Pore water pressure • Effective stress: : & ) ) ∗ %#! : ,) ) - & : ' : − : : ' ) %;< − & 17Dr. Abdulmannan Orabi IUST
  • 18. Stresses in Saturated Soil with Upward Seepage Stress due to self weight Stress at point C, • Total stress: • Pore water pressure: • Effective stress: = & ) ∗ %#! : ,) ) - & > ' > − > > ' %;< − ) & > ' %;< − & Note that h/H2 is the hydraulic gradient i caused by the flow, and therefore 18Dr. Abdulmannan Orabi IUST
  • 19. Total stress Pore water Pressure, u Effective stress DepthDepth Depth Stress due to self weight Stresses in Saturated Soil with Upward Seepage 19Dr. Abdulmannan Orabi IUST
  • 20. Stress due to self weight Stresses in Saturated Soil with Upward Seepage At any depth z, is the pressure of the submerged soil acting downward and is the seepage pressure acting upward. The effective pressure reduces to zero when these two pressures balance. This situation generally is referred to as boiling. > ' %;< − >C & 0 >C %;< & . >C 3. 3+ D2.+ 3 .+2 For most soils, the value of >C varies from 0.9 to 1.1 %;< & > ' 20Dr. Abdulmannan Orabi IUST
  • 21. ) ) 5 6 7 8 Valve (open) ? ( @ AB - Stress due to self weight Stresses in Saturated Soil with Downward Seepage Stress at point A, • Total stress: • Pore water pressure: • Effective stress: * & ) * & ) * ' * − * 0 21Dr. Abdulmannan Orabi IUST
  • 22. Stress at point B, • Total stress: • Pore water pressure • Effective stress: : & ) ) ∗ %#! : ,) ) − - & : ' : − : : ' ) %;< & Stress due to self weight Stresses in Saturated Soil with Downward Seepage 22Dr. Abdulmannan Orabi IUST
  • 23. Stress due to self weight Stress at point C, • Total stress: • Pore water pressure: • Effective stress: = & ) ∗ %#! : ,) − ) - & > ' > − > > ' %;< ) & > ' %;< & Stresses in Saturated Soil with Downward Seepage 23Dr. Abdulmannan Orabi IUST
  • 24. Pore water Pressure, uTotal stress Effective stress DepthDepth Depth Stress due to self weight Stresses in Saturated Soil with Downward Seepage 24Dr. Abdulmannan Orabi IUST
  • 25. Worked Examples Example 1 A soil profile is shown in figure below. Calculate total stress, pore water pressure, and effective stress at A, B, C, and D. D C B A Ground surface G.W.T Sand Clay Sandγ = 16.3 kN/m^3 γ = 15.1 kN/m^3 γ = 19.8 kN/m^3 1.8 m 1.6 m 2.9 m 25Dr. Abdulmannan Orabi IUST
  • 26. Stress due to self weight Total stress Effective stress Pore water pressure DepthDepthDepth γ1 X H1 γ1 X H1 + γ2 X H2 γ1 X H1 + γ2 X H2 + γ3 X H3 γ1 X H1 + γ2 X H2 + γsub X H3 γw X Hw 26Dr. Abdulmannan Orabi IUST
  • 27. To analyze problems such as compressibility of soils, bearing capacity of foundations, stability of embankments, and lateral pressure on earth retaining structures, we need to know the nature of the distribution of stress along a given cross section of the soil profile. Stress due to surface load Introduction 27Dr. Abdulmannan Orabi IUST
  • 28. When a load is applied to the soil surface, it increases the vertical stresses within the soil mass. The increased stresses are greatest directly under the loaded area, but extend indefinitely in all directions. Introduction 28Dr. Abdulmannan Orabi IUST Stress due to surface load
  • 29. •Allowable settlement, usually set by building codes, may control the allowable bearing capacity. •The vertical stress increase with depth must be determined to calculate the amount of settlement that a foundation may undergo Introduction 29Dr. Abdulmannan Orabi IUST Stress due to surface load
  • 30. Introduction Foundations and structures placed on the surface of the earth will produce stresses in the soil These stresses will decrease with the distance from the load How these stresses decrease depends upon the nature of the soil bearing the load 30Dr. Abdulmannan Orabi IUST Stress due to surface load
  • 31. Individual column footings or wheel loads may be replaced by equivalent point loads provided that the stresses are to be calculated at points sufficiently far from the point of application of the point load. Stress Due to a Concentrated Load 31Dr. Abdulmannan Orabi IUST Stress due to surface load
  • 32. Stresses in soil due to surface load Vertical stress due to a concentrated load • Boussinesq’s Formula • Wastergaard Formula Stress Due to a Concentrated Load 32Dr. Abdulmannan Orabi IUST
  • 33. Stress Due to a Concentrated Load Boussinesq’s Formula for Point Loads Joseph Valentin Boussinesq (13 March 1842 – 19 February 1929) was a French mathematician and physicist who made significant contributions to the theory of hydrodynamics, vibration, light, and heat. 33Dr. Abdulmannan Orabi IUST Stresses in soil due to surface load
  • 34. In 1885, Boussinesq developed the mathematical relationships for determining the normal and shear stresses at any point inside a homogenous, elastic and isotropic mediums due to a concentrated point loads located at the surface Vertical Stress in Soil Stress Due to a Concentrated Load 34Dr. Abdulmannan Orabi IUST
  • 35. The soil mass is elastic, isotropic (having identical properties in all direction throughout), homogeneous (identical elastic properties) and semi-infinite depth. The soil is weightless. Stress Due to a Concentrated Load Assumption: 35Dr. Abdulmannan Orabi IUST Vertical Stress in Soil
  • 36. The distribution of σz in the elastic medium is apparently radially symmetrical. The stress is infinite at the surface directly beneath the point load and decreases with the square of the depth. Vertical Stress in Soil Stress Due to a Concentrated Load 36Dr. Abdulmannan Orabi IUST
  • 37. At any given non-zero radius, r, from the point of load application, the vertical stress is zero at the surface, increases to a maximum value at a depth where , approximately, and then decreases with depth. E 39.25° Vertical Stress in Soil Stress Due to a Concentrated Load 37Dr. Abdulmannan Orabi IUST
  • 38. Vertical Stress in Soil According to Boussinesq’s analysis, the vertical stress increase at point A caused by a point load of magnitude P is given by Stress Due to a Concentrated Load D ∆ ∆ M ∆ N O P Q . P D 1 38Dr. Abdulmannan Orabi IUST
  • 39. Vertical Stress in Soil Stress Due to a Concentrated Load According to Boussinesq’s analysis, the vertical stress increase at point A caused by a point load of magnitude P is given by 2 2 5/2 3 1 2 [1 ( / ) ] z P z r z σ π = + 39Dr. Abdulmannan Orabi IUST … … . 7 − 1 1 ∆ . Q or 2z b P I z σ =
  • 40. Equation shows that the vertical stress is Directly proportional to the load Inversely proportional to the depth squared, and Proportional to some function of the ratio ( r/z). Vertical Stress in Soil Stress Due to a Concentrated Load where 2 5/2 3 1 2 [1 ( / ) ] bI r zπ = + 40Dr. Abdulmannan Orabi IUST … … … … . 7 − 2
  • 41. It should be noted that the expression for z is independent of elastic modulus (E) and Poisson’s ratio (µ), i.e. stress increase with depth is a function of geometry only. Vertical Stress in Soil Stress Due to a Concentrated Load 41Dr. Abdulmannan Orabi IUST
  • 42. r/Z IB r/Z IB r/Z IB r/Z IB 0.00 0.4775 0.18 0.4409 0.36 0.3521 0.55 0.2466 0.01 0.4773 0.19 0.4370 0.37 0.3465 0.56 0.2414 0.02 0.477 0.20 0.4329 0.38 0.3408 0.57 0.2363 0.03 0.4764 0.21 0.4286 0.39 0.3351 0.58 0.2313 0.04 0.4756 0.22 0.4242 0.40 0.3294 0.59 0.2263 0.05 0.4745 0.23 0.4197 0.41 0.3238 0.60 0.2214 0.06 0.472 0.24 0.4151 0.42 0.3181 0.61 0.2165 0.07 0.4717 0.25 0.4103 0.43 0.3124 0.62 0.2117 0.08 0.4699 0.26 0.4054 0.44 0.3068 0.63 0.2070 0.09 0.4679 0.27 0.4004 0.45 0.3011 0.64 0.2024 0.1 0.4657 0.28 0.3954 0.46 0.2955 0.65 0.1978 0.11 0.4633 0.29 0.3902 0.47 0.2899 0.66 0.1934 0.12 0.4607 0.30 0.3849 0.48 0.2843 0.67 0.1889 0.13 0.4579 0.31 0.3796 0.49 0.2788 0.68 0.1846 0.14 0.4548 0.32 0.3742 0.50 0.2733 0.69 0.1804 0.15 0.4516 0.33 0.3687 0.51 0.2679 0.70 0.1762 0.16 0.4482 0.34 0.3632 0.52 0.2625 0.71 0.1721 0.17 0.4446 0.35 0.3577 0.53 0.2571 0.72 0.1681 0.54 0.2518 0.73 0.1641 Influence Factor Ib 42Dr. Abdulmannan Orabi IUST
  • 43. r/Z IB r/Z IB r/Z IB r/Z IB 0.74 0.1603 0.94 0.0981 1.14 0.0595 1.34 0.0365 0.75 0.1565 0.95 0.0956 1.15 0.0581 1.35 0.0357 0.76 0.1527 0.96 0.0933 1.16 0.0567 1.36 0.0348 0.77 0.1491 0.97 0.0910 1.17 0.0553 1.37 0.0340 0.78 0.1455 0.98 0.0887 1.18 0.0539 1.38 0.0332 0.79 0.1420 0.99 0.0865 1.19 0.0526 1.39 0.0324 0.80 0.1386 1.0 0.0844 1.20 0.0513 1.40 0.0317 0.81 0.1353 1.01 0.0823 1.21 0.0501 1.41 0.0309 0.82 0.1320 1.02 0.0803 1.22 0.0489 1.42 0.0302 0.83 0.1288 1.03 0.0783 1.23 0.0477 1.43 0.0295 0.84 0.1257 1.04 0.0764 1.24 0.0466 1.44 0.0283 0.85 0.1226 1.05 0.0744 1.25 0.0454 1.45 0.0282 0.86 0.1196 1.06 0.0727 1.26 0.0443 1.46 0.0275 0.87 0.1166 1.07 0.0709 1.27 0.0433 1.47 0.0269 0.88 0.1138 1.08 0.0691 1.28 0.0422 1.48 0.0263 0.89 0.1110 1.09 0.0674 1.29 0.0412 1.49 0.0257 0.90 0.1083 1.10 0.0658 1.30 0.0402 1.50 0.0251 0.91 0.1057 1.11 0.0641 1.31 0.0393 1.51 0.0245 0.92 0.1031 1.12 0.0626 1.32 0.0384 1.52 0.0240 0.93 0.1005 1.13 0.0610 1.33 0.0374 1.53 0.0234 43Dr. Abdulmannan Orabi IUST Influence Factor Ib
  • 44. r/Z IB r/Z IB r/Z IB r/Z IB 1.54 0.0229 1.66 0.0175 1.86 0.0114 2.5 0.0034 1.55 0.0224 1.67 0.0171 1.88 0.0109 2.6 0.0029 1.56 0.0219 1.68 0.0167 1.90 0.0105 2.7 0.0024 1.57 0.0214 1.69 0.0163 1.92 0.0101 2.8 0.0021 1.58 0.0209 1.70 0.0160 1.94 0.0097 2.9 0.0017 1.59 0.0204 1.72 0.0153 1.96 0.0093 3.0 0.0015 1.60 0.0200 1.74 0.0147 1.98 0.0089 3.5 0.0007 1.61 0.0195 1.76 0.0141 2.0 0.0085 4.0 0.0004 1.62 0.0191 1.78 0.0135 2.1 0.0070 4.5 0.0002 1.63 0.0187 1.80 0.0129 2.2 0.0058 5.0 0.0001 1.64 0.0183 1.82 0.0124 2.3 0.0048 1.65 0.0179 1.84 0.0119 2.4 0.0040 44Dr. Abdulmannan Orabi IUST Influence Factor Ib
  • 45. Equation may be used to draw three types of pressure distribution diagram. They are: The vertical stress distribution on a horizontal plane at depth of z below the ground surface The vertical stress distribution on a vertical plane at a distance of r from the load point, and The stress isobar. Vertical Stress in Soil Pressure Distribution Diagram 45Dr. Abdulmannan Orabi IUST
  • 46. The vertical stress distribution on a horizontal plane at depth of z below the ground surface U 5 5 Vertical Stress in Soil Distribution on a horizontal plane 46Dr. Abdulmannan Orabi IUST
  • 47. The vertical stress distribution on a vertical plane at a distance of r from the point load . Vertical Stress in Soil Distribution on a vertical plane O 47Dr. Abdulmannan Orabi IUST
  • 48. U Vertical Stress in Soil Stress isobars An isobar is a line which connects all points of equal stress below the ground surface. In other words, an isobar is a stress contour. 48Dr. Abdulmannan Orabi IUST
  • 49. What is the vertical stress at point A of figure below for the two loads, P1 and P2 ? P1 = 350 kNP2 = 470 kN Z=2.5m 2.3 m1.1 m A Worked Examples Example 2 49Dr. Abdulmannan Orabi IUST
  • 50. A four concentrated forces are located at corners of a rectangular area with dimensions 8 m by 6 m as shown in figure in the next slide. Compute the vertical stress at points A and B, which are located on the lines A – A’ , B – B’ at depth of 4 m below the ground surface. Worked Examples Example 3 50Dr. Abdulmannan Orabi IUST
  • 51. 700 kN700 kN 700 kN700 kN 4 m 4 m 8 m B A’ A B’ Worked Examples Example 3 Dr. Abdulmannan Orabi IUST 51
  • 52. Vertical Stress in Soil Westergaard Formula Westergaard proposed a formula for the computation of vertical stress by a point load, P at the surface as O + 2V + . / In which µ is Poisson’s ratio + 1 − 2X /,2 − 2X- 52Dr. Abdulmannan Orabi IUST … . 7 − 3
  • 53. Vertical Stress in Soil Stress below a Line Load The vertical stress increase due to line load , , inside the soil mass can be determined by using the principles of the theory of elasticity, or 2 V P This equation can be rewritten as / 2 V 1 P 1P P 53Dr. Abdulmannan Orabi IUST … . 7 − 4
  • 54. Vertical Stress in Soil Vertical Stress caused by a horizontal line load The vertical stress increase ( ) at point A in the soil mass caused by a horizontal line load can be given as : 2 P V P 1 / P 54Dr. Abdulmannan Orabi IUST … . 7 − 5
  • 55. Vertical Stress in Soil Vertical Stress caused by a strip load The fundamental equation for the vertical stress increase at a point in a soil mass as the result of a line load can be used to determine the vertical stress at a point caused by a flexible strip load of width B. The term strip loading will be used to indicate a loading that has a finite width along the x axis but an infinite length along the y axis. 55Dr. Abdulmannan Orabi IUST
  • 56. Vertical Stress in Soil Vertical Stress caused by a strip load α β 6 B Vertical stress at point A can be determined by equation: [ sin cos( 2 )]o z q σ α α α β π = + + P 56Dr. Abdulmannan Orabi IUST … . 7 − 6
  • 57. B [ 0.25 0.5 ] ^ 0.5 0.25 Worked Examples Example 4 Refer to figure below, The magnitude of the strip load is 120 kPa. Calculate the vertical stress at points, a , b, and c. 57Dr. Abdulmannan Orabi IUST
  • 58. _ 6 4 " + _ 1 2 2[( )( ) ( )]o z q a b b a a σ α α α π + = + − Vertical Stress Due to Embankment Loading The vertical stress increase in the soil mass due to an embankment of height H may be expressed as Vertical Stress in Soil " )where: `4+ a` ) `4+ a` 58Dr. Abdulmannan Orabi IUST … . 7 − 7
  • 59. ^ 7 6 2 ` 120 aO+ 3 ` 2 ` Refer to figure below. The magnitude of the load is 120 kPa. Calculate the vertical stress at points, A , B, and C. Worked Examples Example 4 59Dr. Abdulmannan Orabi IUST
  • 60. 1- Under the center: The increase in the vertical stress ( ) at depth z ( point A)under the center of a circular area of diameter D = 2R carrying a uniform pressure q is given by Vertical Stress in Soil Vertical Stress due to a uniformly loaded circular area 1 − 1 Q/ 1 / 60Dr. Abdulmannan Orabi IUST … . 7 − 8
  • 61. Vertical Stress in Soil Vertical Stress due to a uniformly loaded circular area 6 6' Q 6' 6 61Dr. Abdulmannan Orabi IUST
  • 62. Vertical Stress in Soil 2- At any point: The increase in the vertical stress ( ) at any point located at a depth z at any distance r from the center of the loaded area can be given Vertical Stress due to a uniformly loaded circular area where and are functions of z/R and r/R. 1' ' 1' ' 62Dr. Abdulmannan Orabi IUST … . 7 − 9
  • 63. Vertical Stress in Soil Vertical Stress due to a uniformly loaded circular area 7 7' . Q 7 7'. 63Dr. Abdulmannan Orabi IUST
  • 64. Vertical Stress in Soil Variation of with z/R and r/R.1' 64Dr. Abdulmannan Orabi IUST
  • 65. Vertical Stress in Soil Variation of with z/R and r/R.1' 65Dr. Abdulmannan Orabi IUST
  • 66. Variation of with z/R and r/R.' Vertical Stress in Soil 66Dr. Abdulmannan Orabi IUST
  • 67. Vertical Stress in Soil Variation of with z/R and r/R.' 67Dr. Abdulmannan Orabi IUST
  • 68. Vertical Stress in Soil Vertical Stress Caused by a Rectangular loaded area The increase in the vertical stress ( ) at depth z under a corner of a rectangular area of dimensions B = m z and L = n z carrying a uniform pressure q is given by: z o zq Iσ = c 3 +3 . 2 0 2 .+ d + 2 where : 68Dr. Abdulmannan Orabi IUST … . 7 − 10
  • 69. Vertical Stress in Soil Vertical Stress Caused by a Rectangular loaded area c 1 4V 2 ` ` 1 ` ` 1 ` 2 ` 1 + e 2 ` ` 1 ` − ` 1 The influence factor can be expressed as ` d + 2 where : 69Dr. Abdulmannan Orabi IUST … . 7 − 11
  • 70. The increase in the stress at any point below a rectangular loaded area can be found by dividing the area into four rectangles. The point A’ is the corner common to all four rectangles. Vertical Stress in Soil Vertical Stress Caused by a Rectangular loaded area 1 2 34 6' * f g c g 70Dr. Abdulmannan Orabi IUST
  • 71. Vertical Stress in Soil Vertical Stress Caused by a Rectangular loaded area 71Dr. Abdulmannan Orabi IUST 4 6' 6' 6' 6' − h5 h5i − h5 + h5 h5 4 3 4 2 9 1 1 2 3 5 5 1 8 7 9 87 4 7 3 * − − f
  • 72. Variation of with m and nc n m 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.1 0.0047 0.0092 0.0132 0.0168 0.0198 0.0222 0.0242 0.0258 0.2 0.0092 0.0179 0.0259 0.0328 0.0387 0.0435 0.0474 0.0504 0.3 0.0132 0.0259 0.0374 0.0474 0.0559 0.0629 0.0686 0.0731 0.4 0.0168 0.0328 0.0474 0.0602 0.0711 0.0801 0.0873 0.0931 0.5 0.0198 0.0387 0.0559 0.0711 0.0840 0.0947 0.1034 0.1104 0.6 0.0222 0.0435 0.0629 0.0801 0.0947 0.1069 0.1168 0.1247 0.7 0.0242 0.0474 0.0686 0.0873 0.1034 0.1169 0.1277 0.1365 0.8 0.0258 0.0504 0.0731 0.0931 0.1104 0.1247 0.1365 0.1461 0.9 0.0270 0.0528 0.0766 0.0977 0.1158 0.1311 0.1436 0.1537 1.0 0.0279 0.0547 0.0794 0.1013 0.1202 0.1361 0.1491 0.1598 72Dr. Abdulmannan Orabi IUST
  • 73. Variation of with m and nc n m 0.9 1 1.2 1.4 1.6 1.8 2.0 2.5 0.1 0.0270 0.0279 0.0293 0.0301 0.0306 0.0309 0.0311 0.0314 0.2 0.0528 0.0547 0.0573 0.0589 0.0599 0.0606 0.0610 0.0616 0.3 0.0766 0.0794 0.0832 0.0856 0.0871 0.0880 0.0887 0.0895 0.4 0.0977 0.1013 0.1063 0.1094 0.1114 0.1126 0.1134 0.1145 0.5 0.1158 0.1202 0.1263 0.1300 0.1324 0.1340 0.1350 0.1363 0.6 0.1311 0.1361 0.1431 0.1475 0.1503 0.1521 0.1533 0.1548 0.7 0.1436 0.1491 0.1570 0.1620 0.1652 0.1672 0.1686 0.1704 0.8 0.1537 0.1598 0.1684 0.1739 0.1774 0.1797 0.1812 0.1832 0.9 0.1619 0.1684 0.1777 0.1836 0.1875 0.1899 0.1915 0.1938 1.0 0.1684 0.1752 0.1851 0.1914 0.1955 0.1981 0.1999 0.2024 73Dr. Abdulmannan Orabi IUST
  • 74. Variation of with m and nc n m 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 1.2 0.0293 0.0573 0.0832 0.1063 0.1263 0.1431 0.1570 0.1684 1.4 0.0301 0.0589 0.0856 0.1094 0.1300 0.1475 0.1620 0.1739 1.6 0.0306 0.0599 0.0871 0.1114 0.1324 0.1503 0.1652 0.1774 1.8 0.0309 0.0606 0.0880 0.1126 0.1340 0.1521 0.1672 0.1797 2.0 0.0311 0.0610 0.0887 0.1134 0.1350 0.1533 0.1686 0.1812 2.5 0.0314 0.0616 0.0895 0.1145 0.1363 0.1548 0.1704 0.1832 3.0 0.0315 0.0618 0.0898 0.1150 0.1368 0.1555 0.1711 0.1841 4.0 0.0316 0.0619 0.0901 0.1153 0.1372 0.1560 0.1717 0.1847 5.0 0.0316 0.0620 0.0901 0.1154 0.1374 0.1561 0.1719 0.1849 6.0 0.0316 0.0620 0.0902 0.1154 0.1374 0.1562 0.1719 0.1850 74Dr. Abdulmannan Orabi IUST
  • 75. Variation of with m and nc n m 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.5 1.2 0.1777 0.1851 0.1958 0.2028 0.2073 0.2103 0.2124 0.2151 1.4 0.1836 0.1914 0.2028 0.2102 0.2151 0.2184 0.2206 0.2236 1.6 0.1874 0.1955 0.2073 0.2151 0.2203 0.2237 0.2261 0.2294 1.8 0.1899 0.1981 0.2103 0.2183 0.2237 0.2274 0.2299 0.2333 2.0 0.1915 0.1999 0.2124 0.2206 0.2261 0.2299 0.2325 0.2361 2.5 0.1938 0.2024 0.2151 0.2236 0.2294 0.2333 0.2361 0.2401 3.0 0.1947 0.2034 0.2163 0.2250 0.2309 0.2350 0.2378 0.2420 4.0 0.1954 0.2042 0.2172 0.2260 0.2320 0.2362 0.2391 0.2434 5.0 0.1956 0.2044 0.2175 0.2263 0.2324 0.2366 0.2395 0.2439 6.0 0.1957 0.2045 0.2176 0.2264 0.2325 0.2367 0.2397 0.2441 75Dr. Abdulmannan Orabi IUST
  • 76. Approximate Method B B + z 2 1 z " O 76Dr. Abdulmannan Orabi IUST 2V:1H method A simple but approximate method is sometimes used for calculating the stress change at various depths as a result of the application of a pressure at the ground surface. The transmission of stress is assumed to follow outward fanning lines at a slope of 1 horizontal to 2 vertical.
  • 77. Approximate Method For uniform footing (B x L) we can estimate the change in vertical stress with depth using the Boston Rule. Assumes stress at depth is constant below foundation influence area B B + z 2 1 z " d ,d - , - " O " O d 77Dr. Abdulmannan Orabi IUST … . 7 − 12 2V:1H method
  • 78. Approximate Method B + z L B z Stress on this plane " j d ∗ Stress on this plane at depth z, " d ,d - , - Rectangular footing B B + z 2 1 78Dr. Abdulmannan Orabi IUST 2V:1H method
  • 79. Newmark Method 79Dr. Abdulmannan Orabi IUST • Stresses due to foundation loads of arbitrary shape applied at the ground surface • Newmark’s chart provides a graphical method for calculating the stress increase due to a uniformly loaded region, of arbitrary shape resting on a deep homogeneous isotropic elastic region.
  • 80. Newmark Method • The Newmark’s Influence Chart method consists of concentric circles drawn to scale, each square contributes a fraction of the stress. • In most charts each square contributes 1/200 (or 0.005) units of stress. (influence value, I) 80Dr. Abdulmannan Orabi IUST
  • 81. Newmark Method 81Dr. Abdulmannan Orabi IUST The use of the chart is based on a factor termed the influence value, determined from the number of units into which the chart is subdivided. Influence value 0.005 A B 1 unit
  • 82. Newmark Method A B Influence value = 0.005 Total number of block on chart = 200 and influence value = 1/200
  • 83. The influence chart may be used to compute the pressure on an element of soil beneath a footing, or from pattern of footings, and for any depth z below the footing. It is only necessary to draw the footing pattern to a scale of z = length AB of the chart. (If z= 6m and AB = 30mm, the scale is 1/200). Newmark Method 83Dr. Abdulmannan Orabi IUST
  • 84. The footing plan will be placed on the influence chart with the point for which the stress is desired at the center of the circles. Newmark Method The units (segments or partial segments) enclosed by the footing are counted, and the increase in stress at the depth z is computed as " c j Where I is the influence factor of the chart. " +00 2 0. . +. + 2+ 3 +3 0. . j `4 . 3 2 , 0+. + +. `+ 2- 84Dr. Abdulmannan Orabi IUST … . 7 − 13