Central Expressway Project Section I
Section from Kadawatha to Meerigama
Estimation of bearing capacity of foundation for Sign board at
Sta. 21+100 LHS
1. Introduction and objectives
A sign board with dimensions of 5557mm x 6330mm to be constructed at Sta. 21+100 (LHS). The
general arrangement is shown in Figure 1. The objective of this report is to design the foundation
arrangement for this particular sign board.
Support C
(23)
Support D
(6)
Support A
(4)
Y
Z
X
Support B
(2)
Figure 1- General arrangement
The critical actions were filtered out for the design, namely maximum compressive force,
maximum tensile force and maximum horizontal force. The dead loads are included in there.
It was noted that loads acting on Support A and B are almost same and same phenomenon
observed for Support C and D.
The summary of critical actions is tabulated in Table 1.1.
1/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
Table 1.1- Summary of critical actions
Support
Limit state
A, B
Load /kN
Moments /kNm
Fx
Fy
Fz
Mx
My
Mz
Compression
6
0
152
0
0
0
C, D
Compression
-31
0
116
0
0
0
A, B
Tension
-4
0
-66
0
0
0
C, D
Tension
28
0
-92
0
0
0
+ compression, - tension
Further following constraints in Table 1.2 were casted to design the foundation system to satisfy
the requirement of structural analysis.
Table 1.2- Design constriants related foundation design
Parameter
Limit
Allowable differential settlement /mm
25
Minimum plan size of the pedestal /m²
1.2 x 1.2
Pedestal height above ground level/m
0.6
Total minimum height of the pedestal /m
2
2. Subsoil condition
As shown in Figure 2.1, BH 21+105 N-L is the nearest boreholes to the location. It is around 5m
away from interested location. The subsoil profile can be summarized as presented in Figure 2.2
and subsoil strength parameters are given in Table 2.1.
Figure 2.1- Borehole layout, 21+105 N-L
2/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
15.150 mMSL
Layer 1- Firm SILT with clay and sand, 3.0m thick
12.150 mMSL
Layer 2 - Loose to M. dense clayey SAND, 2.6 thick
9.550 mMSL
Layer 3- Medium dense SAND, 0.9m thick
8.650 mMSL
mMSL
Layer 4- Very dense silty SAND (CDR), 3.7m thick
4.950 mMSL
Layer 6- Bedrock
Figure 2.2- Subsoil profile
Table 2.1- Subsoil material parameters
BH 21+105 N-L (15.150 mMSL)
Parameters
Layer 1
Layer 2
Layer 3
Layer 4
Firm SILT with
clay and sand
Loose to M.
dense clayey
SAND
Medium dense
SAND
Very dense
silty SAND
(CDR)
Layer thicknesses /m
3
2.6
0.9
3.7
SPT N
4
11
19
>50
Unit weight /kN/m³
16
17
18
20
Undrained cohesion /kPa
20
-
-
-
Drained friction angle /degrees
-
28
31
38
Effective cohesion /kPa
-
5
5
10
Young’s Modulus
3500
17000
22000
40000
Poisons ratio
0.38
0.32
0.30
0.25
Compression ratio
0.15
-
-
-
Recompression ratio
0.015
-
-
-
Overconsolidation ratio
1.0
-
-
-
Type
3/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
3. Calculations
3.1.
Bearing capacity of Foundation for Support A and B
Hansen’s method (1970) of estimating bearing capacity of shallow foundations was used. Layered
soil, that is two-layer subsoil idealization as proposed Bowles (1997) was also incorporated where
ever necessary, especially when a strong layer is underlain by a weak layer.
Calculations were done considering two cases namely,
1. Foundation under compression
2. Foundation in tension
3. Foundation subjected to lateral loads, i.e. sliding
Further, it found out that the dimensions in the Table 3.1 are the minimum requirement based
on the structural details.
Table 3.1- Minimum Dimensions of the foundation system.
Parameter
Value
Remarks
Foundation thickness /m
0.4
Minimum thickness is around 300mm for 4m² area footing
as per foundation designers’s manual by Curtin et.al and
here it was 400mm considering effective stress distribution
through concrete element
Foundation width /m
2.0
Foundation length /m
2.0
Depth to the foundation /m
2.0
Governed by pedestal size (see Table 1.2)
Considering the minimum pedestal height (See Table 1.2)
and foundation thickness
The summary of analysis results is given in Table 3.2 and a sketch of the proposed arrangement
is given in Figure 3.1.
Table 3.2- Summary of the foundation analysis for support A and B
Foundation sizes
Loading
Pedestal sizes
Calculations
situation
Width
Length
Depth
Thickness
Width
Length
Height
Compression
2.00
2.00
3.00
0.40
1.20
1.20
2.20
Tension and
sliding
2.00
2.00
3.00
0.40
1.20
1.20
2.20
Annexure 3.1
Layer 1 (Firm SILT with clay and sand) was completely removed and replaced with rock in order
to satisfy the bearing capacity and settlement requirement.
4/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
Bearing capacity calculation for foundation A& B without rock replacement is presented in
Annexure 3.2
As per above calculation, the minimum dimensions of the footing is satisfactory for both tension
and compression
3.2.
Bearing capacity of Foundation for Support C and D
The same procedure explained in above Section 4.1 is adopted to assess the foundation size of
Support C and D. The obtained results are presented in Table 3.3.
Table 3.3- Proposed sizes of the foundation for support C and D
Foundation sizes
Pedestal sizes
Loading
situation
Width
Length
Depth
Thickness
Width
Length
Height
Compression
2.00
2.00
3.00
0.40
1.20
1.20
3.20
Tension and
Sliding
2.00
2.00
3.00
0.40
1.20
1.20
3.20
Calculations
Annexure 3.3
Layer 1 (Firm SILT with clay and sand) was completely removed and replaced with rock in order to
satisfy the bearing capacity and settlement requirement.
Bearing capacity calculation for foundation A& B without rock replacement is presented in
Annexure 3.4
3.3.
Estimation of Settlement
The method proposed by Schmertmann was used to estimate the immediate settlement while
Terzhghi consolidation theory was used to estimate the consolidation settlement. The summary
of the settlement is presented in Table 3.4
Table 3.4- Summary of settlement analysis
Settlement
/mm
Limit /mm
Compliance
Calculations
A and B (Maximum compression)
4.1
50
Yes
Annexure 3.5
C and D (Maximum compression)
3.3
50
Yes
Annexure 3.6
A, B, C & D (Only self-weigh)
0.4
50
Yes
Annexure 3.7
Differential settlement (max) in mm
3.6
25
Yes
Supports
5/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
4. Conclusions and recommendations

The bearing capacity, sliding, tension/uplift and the settlements of the supports were
investigated and as a result minimum dimensions in Table 4.1 are proposed to foundation
of sign board at Sta. 21+100 LHS.
Table 4.1- Proposed dimensions of the foundations for sign board at Sta. 21+100 LHS
Support
Support A,
B, C and D

Parameter
Value
Type of foundation
Shallow
Width of the foundation /m
2.00
Length of the foundation /m
2.00
Thickness of the foundation /m
0.40
Depth of the foundation /m
2.00
Ground Improvement
Yes
Plan Width of the pedestal /m
1.20
Plan Length of the pedestal /m
1.20
Height of the pedestal above the
footing top level /m
2.20
Allowable bearing capacity /kPa
300
Remarks
Rock replacement up to end of Layer 1,
Firm SILT with clay and sand
(12.15 MSL level)
For 33.3mm settlement and for a
foundation having above parameters
It is to be noted and very important to carry out backfilling properly. Preferably with ABC
material with specified degree of compaction in the specification. Layer by layer
compaction is highly recommended.
6/7
Central Expressway Project Section I
Section from Kadawatha to Meerigama
Figure 4.1- Sketch of the final foundation arrangement (Dimensions are in meters)
7/7
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Sub soil layer 1 (Firm SILT with clay and sand)
Saturated unit weight
γsat
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
Layer thickness
d1
=
3
20
kN/m
20
kN/m
=
40
degrees
=
0
kPa
3
3.0
Sub soil layer 2 (Loose to medium dense clayey SAND)
Saturated unit weight
γsat
=
17
kN/m3
Wet unit weight
γwet
=
16
kN/m3
Friction angle
φ
=
28
degrees
Cohesion
c
=
5
kPa
Layer thickness
d2
2.6
Foundation
Depth
D
=
2
m
Length
L
=
2
m
Width
B
=
2
m
Thickness
t
=
0.4
m
Base inclination o the horizontal
η
=
0
degrees
Ground inclination to the horizontal
β
=
0
degrees
Distance to slope from edge of footing
b
=
0
m
Ground geometry
Loads and Moments
Normal force
V
=
152
kN
Horizontal force parallel to L
H L / HY
=
0
kN
Horizontal force parallel to B
H B / HX
=
6
kN
Moment around axis parallel to L (X axis)
ML / MY
=
0
kNm
Moment around axis parallel to B (Y axis)
MB / MX
=
0
kNm
--------------- Pg 1 / 8 ---------------
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Loads due to Pedestal
Length of Pedestal
LP
=
1.2
m
Width of Pedestal
WP
=
1.2
m
Height of Pedestal
HP
=
2.2
m
Vertical loads due to Pedestal
VP
=
79.20
kN
Eccentricity due to Moments
Bowles
Eccentricity to L direction
eL / eZ
=
0.000
m
Eccentricity to B direction
eB / eX
=
0.000
m
L'
=
2.000
m
B'
=
2.000
m
Foundation influence zone
Depth to water table from EGL
H
Dw
=
=
2.14
0
m
Unit weight of water
γw
=
9.81
Effective unit weight
γeff
=
10.19 kN/m3
Overburden stress
q1
=
20.38 kPa
Effect of water table
Cl 4.7
(pg 249)
--------------- Pg 2 / 8 ---------------
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
1 Estimation of Ultimate Bearing Capacity for Layer 1 (Hansen - 1970)
Bearing capacity factors
Nc
=
75.313
Nq
=
64.195
Nγ
=
79.541
dc
=
1.400
dq
=
1.214
dγ
=
1.000
d'c
=
N/A
k
=
1.000
Depth factors
Load inclination factor
--------------- Pg 3 / 8 ---------------
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Bowles (1997) suggested that α 1 and α 2 as follows, 2 < α 1 < 3 and 3 < α 2 < 4
Hence, following values can be adopted
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
0.0
ic,B
=
0.951
ic,L
=
1.000
iq,B
=
0.951
iq,L
=
1.000
iγ,B
=
0.907
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
Shape factors for inclined loading
Sc,B
=
1.810
Sc,L
=
1.852
Sq,B
=
1.612
Sq,L
=
1.643
Sγ,B
=
0.637
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Bowles
If b > 2B, no need to considered ground modification factors, no reduction
b
=
0.00 m
B
=
2.00 m
gc
=
1.000
gq
=
1.000
gγ
=
1.000
g'c
=
N/A
bc
=
1.000
bq
=
1.000
bγ
=
1.000
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (1)
=
2903.75
kPa
Ultimate bearing capacity for L direction
qu, L (1)
=
3095.81
kPa
Applied pressure ( V+Wfoundation )
qapp (1)
=
67.80
kPa
=
42.83
Base inclination factors
FoS (1)
--------------- Pg 4 / 8 ---------------
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
2 Estimation of Ultimate Bearing Capacity for Layer 2 (Hansen - 1970)
Estimate the bearing capacity of the layer 2 , assuming the properties of layer 2 with
same footing dimensions and overburden of layer 1.
Bowels
Foundation influence zone for layer 2
H
Effective unit weight
γeff
Depth of foundation
D2
=
3
m
Efective depth of layer 1
d1,eff
=
1
m
Overburden stress
q2
=
30.57
kPa
p
=
8
m
Pv
=
25.48
Ks (K0)
=
0.357
Af
=
4
m2
qPunch
=
15.3
kPa
=
1.664
m
7.19
kN/m
3
Calculation of punching resistance of layer 1
Pg.254
Punching resistance
kN/m
Calculation of ultimate bearing capacity of Layer 2
Bearing capacity factors
Depth factors
Nc
=
25.803
dc
=
1.393
Nq
=
14.720
dq
=
1.294
Nγ
=
10.942
dγ
=
1.000
d'c
=
N/A
k
=
0.983
Load inclination factor
α1 , α2 and Af as above
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
4.0
ic,B
=
0.956
ic,L
=
1.000
iq,B
=
0.959
iq,L
=
1.000
iγ,B
=
0.922
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
--------------- Pg 5 / 8 ---------------
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Shape factors for inclined loading
Sc,B
=
1.546
Sc,L
=
1.570
Sq,B
=
1.450
Sq,L
=
1.469
Sγ,B
=
0.631
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Base inclination factors
gc
=
1.000
bc
=
1.000
gq
=
1.000
bq
=
1.000
gγ
=
1.000
bγ
=
1.000
g'c
=
N/A
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (2)
=
1136.99
kPa
Ultimate bearing capacity for L direction
qu, L (2)
=
1200.50
kPa
Applied pressure ( V+Wfoundation )
qapp (2)
=
30.13
kPa
=
37.73
If
FoSBearing > 3
=
37.73
Satisfied
FoS (2)
FoS againts bearing failure
FoS Bearing
[Min of FoS (1) & FoS (2)]
3 Estimation of Sliding Resistance
Sliding is checked under foundation in tension case, since frictional resistance is minimum
Bowles
Cl 4.6
(pg 242)
Passive resistance
Friction angle for passive resistance
φ
=
20
Cohesion for passive resistance
c
=
0
Passive earth pressure coefficient
Kp
=
2.0396
Minimum embedment depth
H
=
2
m
Passive resistance
Pp
=
83.134
kN
FoS on passive resistance for sliding
SF2
=
3
Allowable passive resistance
PP / SF2
=
27.711
--------------- Pg 6 / 8 ---------------
kN
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Frictional resistance
Foundation base friction angle
φ
=
40
Foundation base cohesion
c
=
0
Net vertical load under the foundation
VNet
=
106.26
kN
Base adhesion (0.6C - 1.0C)
Ca
=
0
kPa
Interface friction angle ( base & soil )
δ
=
26.667
degrees
Frictional resistance
PF
=
53.364
kN
FoS on frictional resistance for sliding
SF1
=
3
Allowable frictional resistance
PF / SF1
17.788
kN
Total allowable lateral resistance
=
45.50
kN
Applied maximum horizontal force
=
6.00
kN
4 Estimation of Tension Capacity
Mayerhof
and Adams
(1968)
Bowles
Cl 4.13 (Pg
270)
Tension force on foundation
T
=
--------------- Pg 7 / 8 ---------------
66.0
kN
Satisfied
Annexure 3.1 : Estimation of Bearing Capacity of a Footing A and B with Rock Replacement
Calculation
Reference
Output
Properties of soil uplifted
Conservatively properties of backfilling material or the worst sub soil condition is used
to estimate the tension capacity of foundation.
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
16
kN/m3
=
25
degrees
=
3
kPa
=
3
=
6
=
2.00 m
Tension capacity
H / B ratio
(from Table)
Approximate limiting depth of footing
failure zone
Since
H
=
6.00 m
>
Foundation is considered as
H
D
m
Shallow footing
KU
(Average)
=
1.37
m
(from Table)
=
0.1
=
1.100
Tension capacity due to friction
=
69.59
Tension capacity due to cohesion
=
48.00
kN
Side friction adjustment factor
sf
Weight of foundation + soil uplifted
W
=
106.26
kN
Total tension capacity
TU
=
223.84
kN
FoSTension
=
FoS againts Tension of foundation
… End of the Calculation ...
--------------- Pg 8 / 8 ---------------
3.39
If
FoSTension>2.5
Satisfied
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Sub soil layer 1 (Firm SILT with clay and sand)
Saturated unit weight
γsat
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
Layer thickness
d1
=
3
16
kN/m
15
kN/m
=
0
degrees
=
20
kPa
3
3.0
Sub soil layer 2 (Loose to medium dense clayey SAND)
Saturated unit weight
γsat
=
17
kN/m3
Wet unit weight
γwet
=
16
kN/m3
Friction angle
φ
=
28
degrees
Cohesion
c
=
5
kPa
Layer thickness
d2
2.6
Foundation
Depth
D
=
2
m
Length
L
=
2
m
Width
B
=
2
m
Thickness
t
=
0.4
m
Base inclination o the horizontal
η
=
0
degrees
Ground inclination to the horizontal
β
=
0
degrees
Distance to slope from edge of footing
b
=
0
m
Ground geometry
Loads and Moments
Normal force
V
=
152
kN
Horizontal force parallel to L
H L / HY
=
0
kN
Horizontal force parallel to B
H B / HX
=
6
kN
Moment around axis parallel to L (X axis)
ML / MY
=
0
kNm
Moment around axis parallel to B (Y axis)
MB / MX
=
0
kNm
--------------- Pg 1 / 8 ---------------
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Loads due to Pedestal
Length of Pedestal
LP
=
1.2
m
Width of Pedestal
WP
=
1.2
m
Height of Pedestal
HP
=
2.2
m
Vertical loads due to Pedestal
VP
=
79.20
kN
Eccentricity due to Moments
Bowles
Eccentricity to L direction
eL / eZ
=
0.000
m
Eccentricity to B direction
eB / eX
=
0.000
m
L'
=
2.000
m
B'
=
2.000
m
Foundation influence zone
Depth to water table from EGL
H
Dw
=
=
1.00
0
m
Unit weight of water
γw
=
9.81
Effective unit weight
γeff
=
6.19 kN/m3
Overburden stress
q1
=
12.38 kPa
Effect of water table
Cl 4.7
(pg 249)
--------------- Pg 2 / 8 ---------------
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
1 Estimation of Ultimate Bearing Capacity for Layer 1 (Hansen - 1970)
Bearing capacity factors
Nc
=
5.140
Nq
=
1.000
Nγ
=
0.000
dc
=
N/A
dq
=
N/A
dγ
=
N/A
d'c
=
0.400
k
=
1.000
Depth factors
Load inclination factor
--------------- Pg 3 / 8 ---------------
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Bowles (1997) suggested that α 1 and α 2 as follows, 2 < α 1 < 3 and 3 < α 2 < 4
Hence, following values can be adopted
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
16.0
ic,B
=
N/A
ic,L
=
N/A
iq,B
=
N/A
iq,L
=
N/A
iγ,B
=
N/A
iγ,L
=
N/A
i'c,B
=
0.024
i'c,L
=
0.000
Shape factors for inclined loading
Sc,B
=
N/A
Sc,L
=
N/A
Sq,B
=
N/A
Sq,L
=
N/A
Sγ,B
=
N/A
Sγ,L
=
N/A
S'c,B
=
0.005
S'c,L
=
0.200
Ground modification factors
Bowles
If b > 2B, no need to considered ground modification factors, no reduction
b
=
0.00 m
B
=
2.00 m
gc
=
N/A
gq
=
N/A
gγ
=
N/A
g'c
=
0.000
bc
=
N/A
bq
=
N/A
bγ
=
N/A
b'c
=
0.000
Ultimate bearing capacity for B direction
qu, B (1)
=
154.33
kPa
Ultimate bearing capacity for L direction
qu, L (1)
=
176.86
kPa
Applied pressure ( V+Wfoundation )
qapp (1)
=
67.80
kPa
=
2.28
Base inclination factors
FoS (1)
--------------- Pg 4 / 8 ---------------
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
2 Estimation of Ultimate Bearing Capacity for Layer 2 (Hansen - 1970)
Estimate the bearing capacity of the layer 2 , assuming the properties of layer 2 with
same footing dimensions and overburden of layer 1.
Bowels
Foundation influence zone for layer 2
H
Effective unit weight
γeff
Depth of foundation
D2
=
3
m
Efective depth of layer 1
d1,eff
=
1
m
Overburden stress
q2
=
18.57
kPa
p
=
8
m
Pv
=
15.48
Ks (K0)
=
1.000
Af
=
4
m2
qPunch
=
40.0
kPa
=
1.664
m
7.19
kN/m
3
Calculation of punching resistance of layer 1
Pg.254
Punching resistance
kN/m
Calculation of ultimate bearing capacity of Layer 2
Bearing capacity factors
Depth factors
Nc
=
25.803
dc
=
1.393
Nq
=
14.720
dq
=
1.294
Nγ
=
10.942
dγ
=
1.000
d'c
=
N/A
k
=
0.983
Load inclination factor
α1 , α2 and Af as above
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
4.0
ic,B
=
0.956
ic,L
=
1.000
iq,B
=
0.959
iq,L
=
1.000
iγ,B
=
0.922
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
--------------- Pg 5 / 8 ---------------
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Shape factors for inclined loading
Sc,B
=
1.546
Sc,L
=
1.570
Sq,B
=
1.450
Sq,L
=
1.469
Sγ,B
=
0.631
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Base inclination factors
gc
=
1.000
bc
=
1.000
gq
=
1.000
bq
=
1.000
gγ
=
1.000
bγ
=
1.000
g'c
=
N/A
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (2)
=
843.65
kPa
Ultimate bearing capacity for L direction
qu, L (2)
=
889.31
kPa
Applied pressure ( V+Wfoundation )
qapp (2)
=
30.13
kPa
=
28.00
If
FoSBearing > 3
=
2.28
No
FoS (2)
FoS againts bearing failure
FoS Bearing
[Min of FoS (1) & FoS (2)]
3 Estimation of Sliding Resistance
Sliding is checked under foundation in tension case, since frictional resistance is minimum
Bowles
Cl 4.6
(pg 242)
Passive resistance
Friction angle for passive resistance
φ
=
0
Cohesion for passive resistance
c
=
20
Passive earth pressure coefficient
Kp
=
1
Minimum embedment depth
H
=
2
m
Passive resistance
Pp
=
24.76
kN
FoS on passive resistance for sliding
SF2
=
3
Allowable passive resistance
PP / SF2
=
8.2533
--------------- Pg 6 / 8 ---------------
kN
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Frictional resistance
Foundation base friction angle
φ
=
0
Foundation base cohesion
c
=
20
Net vertical load under the foundation
VNet
=
106.26
kN
Base adhesion (0.6C - 1.0C)
Ca
=
16
kPa
Interface friction angle ( base & soil )
δ
=
0
degrees
Frictional resistance
PF
=
64
kN
FoS on frictional resistance for sliding
SF1
=
3
Allowable frictional resistance
PF / SF1
21.333
kN
Total allowable lateral resistance
=
29.59
kN
Applied maximum horizontal force
=
6.00
kN
4 Estimation of Tension Capacity
Mayerhof
and Adams
(1968)
Bowles
Cl 4.13 (Pg
270)
Tension force on foundation
T
=
--------------- Pg 7 / 8 ---------------
66.0
kN
Satisfied
Annexure 3.2 : Estimation of Bearing Capacity of a Footing A and B without Rock Replacement
Calculation
Reference
Output
Properties of soil uplifted
Conservatively properties of backfilling material or the worst sub soil condition is used
to estimate the tension capacity of foundation.
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
16
kN/m3
=
25
degrees
=
3
kPa
=
3
=
6
=
2.00 m
Tension capacity
H / B ratio
(from Table)
Approximate limiting depth of footing
failure zone
Since
H
=
6.00 m
>
Foundation is considered as
H
D
m
Shallow footing
KU
(Average)
=
1.37
m
(from Table)
=
0.1
=
1.100
Tension capacity due to friction
=
69.59
Tension capacity due to cohesion
=
48.00
kN
Side friction adjustment factor
sf
Weight of foundation + soil uplifted
W
=
106.26
kN
Total tension capacity
TU
=
223.84
kN
FoSTension
=
FoS againts Tension of foundation
… End of the Calculation ...
--------------- Pg 8 / 8 ---------------
3.39
If
FoSTension>2.5
Satisfied
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Sub soil layer 1 (Firm SILT with clay and sand)
Saturated unit weight
γsat
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
Layer thickness
d1
=
3
20
kN/m
20
kN/m
=
40
degrees
=
0
kPa
3
3.0
Sub soil layer 2 (Loose to medium dense clayey SAND)
Saturated unit weight
γsat
=
17
kN/m3
Wet unit weight
γwet
=
16
kN/m3
Friction angle
φ
=
28
degrees
Cohesion
c
=
5
kPa
Layer thickness
d2
2.6
Foundation
Depth
D
=
2
m
Length
L
=
2
m
Width
B
=
2
m
Thickness
t
=
0.4
m
Base inclination o the horizontal
η
=
0
degrees
Ground inclination to the horizontal
β
=
0
degrees
Distance to slope from edge of footing
b
=
0
m
Ground geometry
Loads and Moments
Normal force
V
=
116
kN
Horizontal force parallel to L
H L / HY
=
0
kN
Horizontal force parallel to B
H B / HX
=
31
kN
Moment around axis parallel to L (X axis)
ML / MY
=
0
kNm
Moment around axis parallel to B (Y axis)
MB / MX
=
0
kNm
--------------- Pg 1 / 8 ---------------
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Loads due to Pedestal
Length of Pedestal
LP
=
1.2
m
Width of Pedestal
WP
=
1.2
m
Height of Pedestal
HP
=
2.2
m
Vertical loads due to Pedestal
VP
=
79.20
kN
Eccentricity due to Moments
Bowles
Eccentricity to L direction
eL / eZ
=
0.000
m
Eccentricity to B direction
eB / eX
=
0.000
m
L'
=
2.000
m
B'
=
2.000
m
Foundation influence zone
Depth to water table from EGL
H
Dw
=
=
2.14
0
m
Unit weight of water
γw
=
9.81
Effective unit weight
γeff
=
10.19 kN/m3
Overburden stress
q1
=
20.38 kPa
Effect of water table
Cl 4.7
(pg 249)
--------------- Pg 2 / 8 ---------------
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
1 Estimation of Ultimate Bearing Capacity for Layer 1 (Hansen - 1970)
Bearing capacity factors
Nc
=
75.313
Nq
=
64.195
Nγ
=
79.541
dc
=
1.400
dq
=
1.214
dγ
=
1.000
d'c
=
N/A
k
=
1.000
Depth factors
Load inclination factor
--------------- Pg 3 / 8 ---------------
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Bowles (1997) suggested that α 1 and α 2 as follows, 2 < α 1 < 3 and 3 < α 2 < 4
Hence, following values can be adopted
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
0.0
ic,B
=
0.694
ic,L
=
1.000
iq,B
=
0.699
iq,L
=
1.000
iγ,B
=
0.484
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
Shape factors for inclined loading
Sc,B
=
1.591
Sc,L
=
1.852
Sq,B
=
1.449
Sq,L
=
1.643
Sγ,B
=
0.806
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Bowles
If b > 2B, no need to considered ground modification factors, no reduction
b
=
0.00 m
B
=
2.00 m
gc
=
1.000
gq
=
1.000
gγ
=
1.000
g'c
=
N/A
bc
=
1.000
bq
=
1.000
bγ
=
1.000
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (1)
=
1924.74
kPa
Ultimate bearing capacity for L direction
qu, L (1)
=
3095.81
kPa
Applied pressure ( V+Wfoundation )
qapp (1)
=
58.80
kPa
=
32.73
Base inclination factors
FoS (1)
--------------- Pg 4 / 8 ---------------
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
2 Estimation of Ultimate Bearing Capacity for Layer 2 (Hansen - 1970)
Estimate the bearing capacity of the layer 2 , assuming the properties of layer 2 with
same footing dimensions and overburden of layer 1.
Bowels
Foundation influence zone for layer 2
H
Effective unit weight
γeff
Depth of foundation
D2
=
3
m
Efective depth of layer 1
d1,eff
=
1
m
Overburden stress
q2
=
30.57
kPa
p
=
8
m
Pv
=
25.48
Ks (K0)
=
0.357
Af
=
4
m2
qPunch
=
15.3
kPa
=
1.664
m
7.19
kN/m
3
Calculation of punching resistance of layer 1
Pg.254
Punching resistance
kN/m
Calculation of ultimate bearing capacity of Layer 2
Bearing capacity factors
Depth factors
Nc
=
25.803
dc
=
1.393
Nq
=
14.720
dq
=
1.294
Nγ
=
10.942
dγ
=
1.000
d'c
=
N/A
k
=
0.983
Load inclination factor
α1 , α2 and Af as above
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
4.0
ic,B
=
0.738
ic,L
=
1.000
iq,B
=
0.755
iq,L
=
1.000
iγ,B
=
0.570
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
--------------- Pg 5 / 8 ---------------
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Shape factors for inclined loading
Sc,B
=
1.421
Sc,L
=
1.570
Sq,B
=
1.355
Sq,L
=
1.469
Sγ,B
=
0.772
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Base inclination factors
gc
=
1.000
bc
=
1.000
gq
=
1.000
bq
=
1.000
gγ
=
1.000
bγ
=
1.000
g'c
=
N/A
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (2)
=
834.26
kPa
Ultimate bearing capacity for L direction
qu, L (2)
=
1200.50
kPa
Applied pressure ( V+Wfoundation )
qapp (2)
=
26.13
kPa
=
31.92
If
FoSBearing > 3
=
31.92
Satisfied
FoS (2)
FoS againts bearing failure
FoS Bearing
[Min of FoS (1) & FoS (2)]
3 Estimation of Sliding Resistance
Sliding is checked under foundation in tension case, since frictional resistance is minimum
Bowles
Cl 4.6
(pg 242)
Passive resistance
Friction angle for passive resistance
φ
=
0
Cohesion for passive resistance
c
=
20
Passive earth pressure coefficient
Kp
=
1
Minimum embedment depth
H
=
2
m
Passive resistance
Pp
=
40.76
kN
FoS on passive resistance for sliding
SF2
=
3
Allowable passive resistance
PP / SF2
=
13.587
--------------- Pg 6 / 8 ---------------
kN
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Frictional resistance
Foundation base friction angle
φ
=
40
Foundation base cohesion
c
=
0
Net vertical load under the foundation
VNet
=
114.45
kN
Base adhesion (0.6C - 1.0C)
Ca
=
0
kPa
Interface friction angle ( base & soil )
δ
=
26.667
degrees
Frictional resistance
PF
=
57.478
kN
FoS on frictional resistance for sliding
SF1
=
3
Allowable frictional resistance
PF / SF1
19.159
kN
Total allowable lateral resistance
=
32.75
kN
Applied maximum horizontal force
=
31.00
kN
4 Estimation of Tension Capacity
Mayerhof
and Adams
(1968)
Bowles
Cl 4.13 (Pg
270)
Tension force on foundation
T
=
--------------- Pg 7 / 8 ---------------
92.0
kN
Satisfied
Annexure 3.3 : Estimation of Bearing Capacity of a Footing C & D with Rock Replacement
Calculation
Reference
Output
Properties of soil uplifted
Conservatively properties of backfilling material or the worst sub soil condition is used
to estimate the tension capacity of foundation.
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
18
kN/m3
=
32
degrees
=
5
kPa
=
4.4
=
8.8
=
2.00 m
Tension capacity
H / B ratio
(from Table)
Approximate limiting depth of footing
failure zone
Since
H
=
8.80 m
>
Foundation is considered as
H
D
m
Shallow footing
KU
(Average)
=
1.61
m
(from Table)
=
0.19
=
1.190
Tension capacity due to friction
=
157.32
Tension capacity due to cohesion
=
80.00
kN
Side friction adjustment factor
sf
Weight of foundation + soil uplifted
W
=
114.45
kN
Total tension capacity
TU
=
351.77
kN
FoSTension
=
FoS againts Tension of foundation
… End of the Calculation ...
--------------- Pg 8 / 8 ---------------
3.82
If
FoSTension>2.5
Satisfied
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Sub soil layer 1 (Firm SILT with clay and sand)
Saturated unit weight
γsat
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
Layer thickness
d1
=
3
16
kN/m
15
kN/m
=
0
degrees
=
20
kPa
3
3.0
Sub soil layer 2 (Loose to medium dense clayey SAND)
Saturated unit weight
γsat
=
17
kN/m3
Wet unit weight
γwet
=
16
kN/m3
Friction angle
φ
=
28
degrees
Cohesion
c
=
5
kPa
Layer thickness
d2
2.6
Foundation
Depth
D
=
2
m
Length
L
=
2
m
Width
B
=
2
m
Thickness
t
=
0.4
m
Base inclination o the horizontal
η
=
0
degrees
Ground inclination to the horizontal
β
=
0
degrees
Distance to slope from edge of footing
b
=
0
m
Ground geometry
Loads and Moments
Normal force
V
=
116
kN
Horizontal force parallel to L
H L / HY
=
0
kN
Horizontal force parallel to B
H B / HX
=
31
kN
Moment around axis parallel to L (X axis)
ML / MY
=
0
kNm
Moment around axis parallel to B (Y axis)
MB / MX
=
0
kNm
--------------- Pg 1 / 8 ---------------
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Loads due to Pedestal
Length of Pedestal
LP
=
1.2
m
Width of Pedestal
WP
=
1.2
m
Height of Pedestal
HP
=
2.2
m
Vertical loads due to Pedestal
VP
=
79.20
kN
Eccentricity due to Moments
Bowles
Eccentricity to L direction
eL / eZ
=
0.000
m
Eccentricity to B direction
eB / eX
=
0.000
m
L'
=
2.000
m
B'
=
2.000
m
Foundation influence zone
Depth to water table from EGL
H
Dw
=
=
1.00
0
m
Unit weight of water
γw
=
9.81
Effective unit weight
γeff
=
6.19 kN/m3
Overburden stress
q1
=
12.38 kPa
Effect of water table
Cl 4.7
(pg 249)
--------------- Pg 2 / 8 ---------------
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
1 Estimation of Ultimate Bearing Capacity for Layer 1 (Hansen - 1970)
Bearing capacity factors
Nc
=
5.140
Nq
=
1.000
Nγ
=
0.000
dc
=
N/A
dq
=
N/A
dγ
=
N/A
d'c
=
0.400
k
=
1.000
Depth factors
Load inclination factor
--------------- Pg 3 / 8 ---------------
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Bowles (1997) suggested that α 1 and α 2 as follows, 2 < α 1 < 3 and 3 < α 2 < 4
Hence, following values can be adopted
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
16.0
ic,B
=
N/A
ic,L
=
N/A
iq,B
=
N/A
iq,L
=
N/A
iγ,B
=
N/A
iγ,L
=
N/A
i'c,B
=
0.141
i'c,L
=
0.000
Shape factors for inclined loading
Sc,B
=
N/A
Sc,L
=
N/A
Sq,B
=
N/A
Sq,L
=
N/A
Sγ,B
=
N/A
Sγ,L
=
N/A
S'c,B
=
0.028
S'c,L
=
0.200
Ground modification factors
Bowles
If b > 2B, no need to considered ground modification factors, no reduction
b
=
0.00 m
B
=
2.00 m
gc
=
N/A
gq
=
N/A
gγ
=
N/A
g'c
=
0.000
bc
=
N/A
bq
=
N/A
bγ
=
N/A
b'c
=
0.000
Ultimate bearing capacity for B direction
qu, B (1)
=
144.71
kPa
Ultimate bearing capacity for L direction
qu, L (1)
=
176.86
kPa
Applied pressure ( V+Wfoundation )
qapp (1)
=
58.80
kPa
=
2.46
Base inclination factors
FoS (1)
--------------- Pg 4 / 8 ---------------
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
2 Estimation of Ultimate Bearing Capacity for Layer 2 (Hansen - 1970)
Estimate the bearing capacity of the layer 2 , assuming the properties of layer 2 with
same footing dimensions and overburden of layer 1.
Bowels
Foundation influence zone for layer 2
H
Effective unit weight
γeff
Depth of foundation
D2
=
3
m
Efective depth of layer 1
d1,eff
=
1
m
Overburden stress
q2
=
18.57
kPa
p
=
8
m
Pv
=
15.48
Ks (K0)
=
1.000
Af
=
4
m2
qPunch
=
40.0
kPa
=
1.664
m
7.19
kN/m
3
Calculation of punching resistance of layer 1
Pg.254
Punching resistance
kN/m
Calculation of ultimate bearing capacity of Layer 2
Bearing capacity factors
Depth factors
Nc
=
25.803
dc
=
1.393
Nq
=
14.720
dq
=
1.294
Nγ
=
10.942
dγ
=
1.000
d'c
=
N/A
k
=
0.983
Load inclination factor
α1 , α2 and Af as above
α1
=
2.50
α2
=
3.50
Effective footing area (Af = B'L')
Af
=
4.00
Base adhesion (0.6C - 1.0C)
Ca
=
4.0
ic,B
=
0.738
ic,L
=
1.000
iq,B
=
0.755
iq,L
=
1.000
iγ,B
=
0.570
iγ,L
=
1.000
i'c,B
=
N/A
i'c,L
=
N/A
--------------- Pg 5 / 8 ---------------
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Shape factors for inclined loading
Sc,B
=
1.421
Sc,L
=
1.570
Sq,B
=
1.355
Sq,L
=
1.469
Sγ,B
=
0.772
Sγ,L
=
0.600
S'c,B
=
N/A
S'c,L
=
N/A
Ground modification factors
Base inclination factors
gc
=
1.000
bc
=
1.000
gq
=
1.000
bq
=
1.000
gγ
=
1.000
bγ
=
1.000
g'c
=
N/A
b'c
=
N/A
Ultimate bearing capacity for B direction
qu, B (2)
=
625.03
kPa
Ultimate bearing capacity for L direction
qu, L (2)
=
889.31
kPa
Applied pressure ( V+Wfoundation )
qapp (2)
=
26.13
kPa
=
23.92
If
FoSBearing < 3
=
2.46
No
FoS (2)
FoS againts bearing failure
FoS Bearing
[Min of FoS (1) & FoS (2)]
3 Estimation of Sliding Resistance
Sliding is checked under foundation in tension case, since frictional resistance is minimum
Bowles
Cl 4.6
(pg 242)
Passive resistance
Friction angle for passive resistance
φ
=
0
Cohesion for passive resistance
c
=
20
Passive earth pressure coefficient
Kp
=
1
Minimum embedment depth
H
=
2
m
Passive resistance
Pp
=
24.76
kN
FoS on passive resistance for sliding
SF2
=
3
Allowable passive resistance
PP / SF2
=
8.2533
--------------- Pg 6 / 8 ---------------
kN
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Frictional resistance
Foundation base friction angle
φ
=
0
Foundation base cohesion
c
=
20
Net vertical load under the foundation
VNet
=
106.26
kN
Base adhesion (0.6C - 1.0C)
Ca
=
16
kPa
Interface friction angle ( base & soil )
δ
=
0
degrees
Frictional resistance
PF
=
64
kN
FoS on frictional resistance for sliding
SF1
=
3
Allowable frictional resistance
PF / SF1
21.333
kN
Total allowable lateral resistance
=
29.59
kN
Applied maximum horizontal force
=
31.00
kN
4 Estimation of Tension Capacity
Mayerhof
and Adams
(1968)
Bowles
Cl 4.13 (Pg
270)
Tension force on foundation
T
=
--------------- Pg 7 / 8 ---------------
92.0
kN
No
Annexure 3.4 : Estimation of Bearing Capacity of a Footing C & D without Rock Replacement
Calculation
Reference
Output
Properties of soil uplifted
Conservatively properties of backfilling material or the worst sub soil condition is used
to estimate the tension capacity of foundation.
Wet unit weight
γwet
Friction angle
φ
Cohesion
c
16
kN/m3
=
25
degrees
=
3
kPa
=
3
=
6
=
2.00 m
Tension capacity
H / B ratio
(from Table)
Approximate limiting depth of footing
failure zone
Since
H
=
6.00 m
>
Foundation is considered as
H
D
m
Shallow footing
KU
(Average)
=
1.37
m
(from Table)
=
0.1
=
1.100
Tension capacity due to friction
=
69.59
Tension capacity due to cohesion
=
48.00
kN
Side friction adjustment factor
sf
Weight of foundation + soil uplifted
W
=
106.26
kN
Total tension capacity
TU
=
223.84
kN
FoSTension
=
FoS againts Tension of foundation
… End of the Calculation ...
--------------- Pg 8 / 8 ---------------
2.43
If
FoSTension<2.5
No
Annexure 3.5 : Estimation of Immediate Settlement on Footing A & B (Max Compression)
The settlement of granular soils can also be evaluated by the use of a semiempirical strain
influence factor proposed by Schmertmann et al. (1978).
Applied stress under the Foundation
Q
76.8
kPa
Depth of Foundation
D
2
m
Width of Foundation
B
2
m
Length of Foundation
L
2
m
Effective stress at the base of Foundation (q = γD)
q
16.38
kPa
Effective unit weight of soil
γ
8.19
kN/m3
Correction factor for deph of Foundation
C1
0.86
Correction factor to account for creep in soil
C2
1.20
(Assune time for creep one year)
The following relations are suggested by Salgado (2008) for interpolation
L/B
Iz at z=0
z1
=
=
1.00
0.1000 m
1.000 m
<=0.2
<=1.0 x B
z2
=
4.000 m
<=4.0 x B
q(z1)
24.57 kPa
Iz(m)
=
0.657
Layer No
Δz
Es
Zmid
Iz (mid)
Iz x Δz / Es (m3/kN)
Rock
1.000
50000
0.500
0.378
7.57E-06
2
0.000
17000
1.000
0.657
0.00E+00
2
2.600
17000
2.300
0.372
5.69E-05
3
0.400
22000
3.800
0.044
7.96E-07
Σ
Immediate Settlement of the Foundation
Up to Z1
Z1 to Z2
6.53E-05
S
4.1
mm
Annexure 3.6 : Estimation of Immediate Settlement on Footing C & D (Max Compression)
The settlement of granular soils can also be evaluated by the use of a semiempirical strain
influence factor proposed by Schmertmann et al. (1978).
Applied stress under the Foundation
Q
67.8
kPa
Depth of Foundation
D
2
m
Width of Foundation
B
2
m
Length of Foundation
L
2
m
Effective stress at the base of Foundation (q = γD)
q
16.38
kPa
Effective unit weight of soil
γ
8.19
kN/m3
Correction factor for deph of Foundation
C1
0.84
Correction factor to account for creep in soil
C2
1.20
(Assune time for creep one year)
The following relations are suggested by Salgado (2008) for interpolation
L/B
Iz at z=0
z1
=
=
1.00
0.1000 m
1.000 m
<=0.2
<=1.0 x B
z2
=
4.000 m
<=4.0 x B
q(z1)
24.57 kPa
Iz(m)
=
0.645
Layer No
Δz
Es
Zmid
Iz (mid)
Iz x Δz / Es (m3/kN)
Rock
1.000
50000
0.500
0.372
7.45E-06
2
0.000
17000
1.000
0.645
0.00E+00
2
2.600
17000
2.300
0.365
5.59E-05
3
0.400
22000
3.800
0.043
7.81E-07
Σ
Immediate Settlement of the Foundation
Up to Z1
Z1 to Z2
6.41E-05
S
3.3
mm
Annexure 3.7 : Estimation of Immediate Settlement on Footing (Self-weight only)
The settlement of granular soils can also be evaluated by the use of a semiempirical strain
influence factor proposed by Schmertmann et al. (1978).
Applied stress under the Foundation
Q
29.8
kPa
Depth of Foundation
D
2
m
Width of Foundation
B
2
m
Length of Foundation
L
2
m
Effective stress at the base of Foundation (q = γD)
q
16.38
kPa
Effective unit weight of soil
γ
8.19
kN/m3
Correction factor for deph of Foundation
C1
0.39
Correction factor to account for creep in soil
C2
1.20
(Assune time for creep one year)
The following relations are suggested by Salgado (2008) for interpolation
L/B
Iz at z=0
z1
=
=
1.00
0.1000 m
1.000 m
<=0.2
<=1.0 x B
z2
=
4.000 m
<=4.0 x B
q(z1)
24.57 kPa
Iz(m)
=
0.574
Layer No
Δz
Es
Zmid
Iz (mid)
Iz x Δz / Es (m3/kN)
Rock
1.000
50000
0.500
0.337
6.74E-06
2
0.000
17000
1.000
0.574
0.00E+00
2
2.600
17000
2.300
0.325
4.97E-05
3
0.400
22000
3.800
0.038
6.96E-07
Σ
Immediate Settlement of the Foundation
Up to Z1
Z1 to Z2
5.72E-05
S
0.4
mm