1. SETTLEMENT Of
SHALLOW FOUNDATION

2. 2 types of settlement Elastic ( Immediate ) settlement
Time independent
Causes:
Elastic deformation of dry soil particles
Consolidation settlement
Time dependant
Causes:
Water expulsion

3. ONE DIMENSIONAL CONSOLIDATION TEST
CONSOLIDATION SETTLEMENT
To calculate the consolidation settlement we have to perform
ONE DIMENSIONAL CONSOLIDATION TEST
Consolidometer
Audiometer

4. P4<< P3 << P2 << P1
time P1 P2 P3 P4
deformation
P4<< P3 << P2 << P1

5. I II
III

6. Total settlement S = S1 + S2 + S3
I – Initial compression
II – Primary Consolidation
III – Secondary Settlement
I – Initial compression S1
Causes: imperfect contact surface, loading, particles relocation
II – Primary Consolidation S2
Causes: water expulsion
III – Secondary Settlement S3
Causes: Particles relocation, Particles deformation, Particles destruction
Total settlement S = S1 + S2 + S3

7. e eo e1 e2 While P2 is greater than P1 e2 is smaller than e1 Log P
P1 P2

8. e Cc Cc Compression Index
We can use any curve because the slope is the same Cc
The slope from the curve
Cc = ( LL – 10 ) for undisturbed samples
Cc = ( LL – 10 ) for remolded samples
Log P

9. Pc Soil History PRECONSOLIDATION PRESSURE
We can find Soil History by finding what is called
PRECONSOLIDATION PRESSURE Or
Max Past Effective Overburden Pressure Pc

10. e Pc
Log P

11. OCC – Over Consolidated Clay
Based on values of Pc
Clay soils may be
NCC – Normally Consolidated Clay
OCC – Over Consolidated Clay

12. P Cc Pc Po NCC – Normally Consolidated Clay.
Where Po is greater than Pc
Pc = Max Past Effective Overburden Pressure
Po = Max Present Effective Overburden Pressure P
The slope of the curve in this area is Cc Cc Pc Po

13. P Po Pc OCC – Over Consolidated Clay. Where Po is smaller than Pc
Pc = Max Past Effective Overburden Pressure
Po = Max Present Effective Overburden Pressure P
The slope of the curve in this area is Cs Cs Po Pc

14. Cs
NCC Cc
OCC Pc

15. Total settlement S = Si + Sp + Ss
INITIAL COMPRESSION ( Si )
PRIMARY CONSOLIDATION SETTLEMENT ( Sp )
SECONDARY SETTLEMENT ( Ss ) ep

16. Cα=
/log( )
Ss = C’α H log( )
C’α = ep Cα t1 t2

17. Iρ Si = q B INITIAL COMPRESSION ( Si ) Where: q- net applied pressure
B- width of footing
Poisson’s ratio (tab. 6.6 p 167)
E- modulus of elasticity (tab. 6.5 p 167)
Iρ- influence factor (tab. 6.4 p 167)
Poisson’s ratio (tab. 6.6 p 167)
E- modulus of elasticity (tab. 6.5 p 167)
Iρ- influence factor (tab. 6.4 p 167)

18. TIME RATE OF SETTLEMENT

19. Iρ Iρ < summary S = ) Immediate settlement Si = q B Si = q B NCC
Initial compression
Si = q B
NCC
Primary consolidation
S =
P0 + ΔP Pc
OCC
Consolidation settlement Pc
P0 + ΔP
<
Ss = C’α H log( )
Secondary settlement

20. Settlement due to surcharge
S = f ( P, soil, Z, X, load application type )
Load application types: point
line
strip
circle
square
rectangle
irregular

21. A- Elastic or immediate settlement
The settlement of a foundation can be divided into two major categories:
A- Elastic or immediate settlement
B- Consolidation settlement

22. Immediate or Elastic Settlement
Consolidation Settlement
Secondary Settlement
Time

23. For the calculation of foundation settlement, it is required to determine the vertical stress increase in the soil mass due to the load applied on the foundation.
This chapter is divided into the following three parts:
Procedure for calculation of vertical stress increase
Elastic settlement calculation
Consolidation settlement calculation

25. dr. isam jardaneh / foundation engineering 61303 / 2010

33. 2 : 1 Method
dr. isam jardaneh / foundation engineering / 2010

35. Average Vertical Stress Increase Due to a Rectangularly Loaded Area
As suggested by Griffiths 1984, to find average pressure increase between z = H1 and z = H2 below the corner of a uniformly loaded rectangular area

39. Elastic Settlement Elastic settlement Based on The Theory of Elasticity

40. Elastic Settlement Based on The Theory of Elasticity

46. dr. isam jardaneh / foundation engineering 61303 / 2010

47. dr. isam jardaneh / foundation engineering 61303 / 2010

52. Elastic Settlement of Foundation on Saturated Clay

54. Settlement of Sandy Soil: Use of Strain Influence Factor

56. Continuous Footing

57. Need Interpolation ???

58. Influence Factor Method
Example
q = 160 KN/m²
Find
Elastic Settlement
After 5 years
Using
Influence Factor Method
1.5m
γ = 17.8 KN/mᶟ
3 x 3 m
3x3m
E KN/m²
1.0m
8000
10000
3.0m
16000

59. 0.1 1m
0.5m
0.5
2.5m 2m

60. ∑ = 1.55x10¯⁴ Depth m ΔZ Es KN/m² Average Iz ----- ΔZ mᶟ/KN 0.0 – 1.0
8000
0.233
0.291x10¯⁴
1.0 – 1.5
0.5
10000
0.433
0.217x10¯⁴
1.5 – 4.0
2.5
0.361
0.903x10¯⁴
4.0 – 6.0
2.0
16000
0.111
0.139x10¯⁴
∑ = 1.55x10¯⁴ Iz Es

61. q
C1 = ( ---- ) = [ ] = 0.9
C2 = log (5/0.1) = 1.34
Se = C1 C2 ( q – q ) ∑ (Iz/E)Δz
Se = 24.9 mm
17.8x1.5 _
q - q
160 – (17.8x1.5) ‒

62. Range of Materials Parameters for Computing Settlement

63. Range of Materials Parameters for Computing Settlement

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72. Example 1

73. Example 2

83. Problem # 1

84. Problem # 2

85. Problem # 3

86. Problem # 4
Estimate the consolidation settlement of the clay layer shown in Figure below using 2:1 method and trapezoidal rule. Note 1 ton = 2000 lb.