This document summarizes a seminar on forensic civil engineering regarding the assessment of pile group integrity due to pile eccentricities and failures. It discusses developing charts to evaluate the maximum allowable eccentricity of pile groups and optimal locations for additional or replacement piles when eccentricities or failures render the pile group unsafe. The document provides an example calculation checking the integrity of a 4-pile group with eccentric piles and determining the need for an additional pile based on the pile loads and eccentricities.

1. FORENSIC CIVIL ENGINEERING SEMINAR
ForCES ‘18
29th & 30th Oct. 2018
utm kuala lumpur
MAY 2017

2. THE ASSESSEMENT OF PILE GROUP
INTEGRITY DUE TO PILE
ECCENTRICITIES & FAILURES
ir azhar ahmad school of civil engineering
Email: azharahmad@utm.my
MAY 2017

3. The following course notes are specifically for
use in ‘Assessment of Pile Group Integrity due
to Pile Eccentricities & Failures’ only. Any
reproduction or public display of the contents
beyond this short course is prohibited without
prior consent of the author.

4. ABSTRACT

5. ABSTRACT
 The mode of driving precast reinforced concrete piles on site
is without doubt among the most ‘error prone’ trades of a
construction process. The short comings of driving pre
designated piles at pin point accuracy at exactly the correct
position on the ground has given rise to the caption of ‘pile
eccentricity’ of nearly all individual piles within a pile group.
 This then raises questions of integrity or how safe and
reliable are pile caps that has been designed earlier with zero
pile eccentricities. Questions of how much an eccentricity
limit can be allowed for each pile or rather pile group
arrangements such that previous pile cap designs are still safe
and applicable has to be addressed.
5

6.  Thus one of the aims of this study is to evaluate the
maximum allowable eccentricity of several common pile
group arrangements. Results of this study indicates that the
norm of adopting a maximum allowable eccentricity value of
75 mm for each individual pile irrespective of pile size, pile
working load, pile spacing & column loads is quite misleading
and may result in an unsafe pile group performance!
6
ABSTRACT

7. Rather, results from this study suggests that the critical factor is
not the eccentricity of individual piles but the overall net pile
group eccentricity. This causes eccentric moments to act in the
pile group which in turn governs the redistributed load to each
individual pile within the pile group. This redistributed loads are
then compared to the pile safe working load to establish a
‘Pass-Fail’ criteria.
< Pile Safe Working Load
Fp: Redistributed Loads to each individual pile kN
N : Net Column Service Load kN (incl self weight of pile cap)
n : Pile Safe Working Load kN
7
ABSTRACT

8. 8
Pile Group Centroid after ecc
ABSTRACT
X Axis
YAxis
Mx
My
+Ymm
+ X mm

9.  Moreover this study has shown that
i. the ratio of net column service load over pile safe working
load (N/n Ratio)
ii. the centre to centre pile spacing (K Factor)
both have significant impact on the net pile group
eccentricity limits.
9
ABSTRACT

10. ACKNOWLEDGEMENT
Tasnim Arif
Heart felt gratitude and appreciation to all my
‘Undergraduate Students’ that have toiled and given
their upmost effort in completing this research
work….may Allah bestow His blessings onto each
and every one of you……ameenn

11. ACKNOWLEDGEMENT
N.Syafa Izzatie
Aziz KaplanAbdul Aziz Jeddawy

12. ACKNOWLEDGEMENT
Nadzirah Fozi Hafizah Hambali
Wan Rasydan

13. Norsharizal Sahlan Irmawaty Ahmad Mohd Rizal Deris
ACKNOWLEDGEMENT

14. ACKNOWLEDGEMENT
Nor Syahida Nur Shamsul Bariah Azmazanzan Arshad Sharifudin

15. ACKNOWLEDGEMENT
Sufi Syahirah Haifa Fakhira Fardah Manirah Siti Zahri’iyah Nor Ainsha

16. PART 1: EXECUTIVE SUMMARY

17. 17
EXECUTIVE SUMMARY
1.0 The development of a Net Pile Group
Eccentricity Limit Chart. These charts can
be referred to evaluate the safety and
reliability of pile caps that has been designed
earlier by ignoring pile eccentricities against
actual pile eccentricities recorded on site.

18. 18
0, 268
268, 0
0, 268
-268, 0
0, -268
268, 0
0, -268
-268, 0
-300
-200
-100
0
100
200
300
-300 -200 -100 0 100 200 300
4 PILE GROUP : NET PILE GROUP
ECCENTRICITY LIMIT CHART
N/n=3.50
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)
EXECUTIVE SUMMARY

19. 19
EXECUTIVE SUMMARY
0, 420
420, 0
0, 420
-420, 0
0, -420
420, 0
0, -420
-420, 0
0, 268
268, 0
0, 268
-268, 0
0, -268
268, 0
0, -268
-268, 0
0, 136
136, 0
0, 136
-136, 0
0, -136
136, 0
0, -136
-136, 0
-500
-400
-300
-200
-100
0
100
200
300
400
500
-500 -400 -300 -200 -100 0 100 200 300 400 500
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT CHART
(250mm Square Pile @ 175 kN Working Load)
N/n=3.25 N/n=3.50 N/n=3.75
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)

20. 20
2.0 The development of an Optimum Add-On
Pile Location Chart. Where eccentricities
beyond ‘allowable’ limits occur, this will
render pile groups and the subsequent pile
caps as ‘unsafe’ to sustain column loads due
to eccentric moments which causes loads
distributed to piles to be greater than the pile
working load capacities! The most practical
solution usually adopted on site to rectify this
problem is by installing additional or ‘add-on’
pile/s.
EXECUTIVE SUMMARY

21. 21
-1,000
-800
-600
-400
-200
0
200
400
600
800
1,000
-250 -200 -150 -100 -50 0 50 100 150 200 250
4 PILE GROUP CENTROID PRIOR TO 'ADD-ON' PILE
4 PILE GROUP: OPTIMUM POSITION OF
'ADD-ON' SINGLE PILE
250 mm Square RC Pile
ADD-ONPILECOORDINATE
EXECUTIVE SUMMARY

22. 22
3.0 The development of an Optimum
Replacement Pile Location Chart. Where
pile failure occurs during driving, this will
render pile groups and the subsequent pile
caps as ‘unsafe’ to sustain column loads due
to eccentric moments which causes loads
distributed to piles to be greater than the pile
working load capacities! The most practical
solution usually adopted on site to rectify this
problem is by installing replacement pile/s.
EXECUTIVE SUMMARY

23. 23
-375
-450
-525
-600
-675
-300
-225
-150
-75
0
375
300
225
150
75
450
525
600
675
750
-800
-600
-400
-200
0
200
400
600
800
1000
-500 -400 -300 -200 -100 0 100 200 300 400
4 PILE GROUP: OPTIMUM NET COORDINATES OF
REPLACEMENT PILE RP1 & RP2 (PILE FAILURE @ P#1)
OPTIMUM X @P1 FAIL OPTIMUM Y @P1 FAIL
REPLACEMENTPILECOORDINATE
NET ECCENTRICITY OF PILE GROUP (BEFORE PILE REPLACEMENT)
EXECUTIVE SUMMARY

24. PART 2: PILE ECCENTRICITY
CHECK

25. 25
+Ymm
+ X mm
PILE ECCENTRICITY CHECK
Pile P#1 Y = 33 mm
Net X
ecc
Net Y
ecc
X = -28 mm(mm) (mm)
-41 140
Pile P#2 Y = 77 mm
X = 101 mm
Pile P#3 Y = 83 mm
X = -97 mm
Pile P#4 Y = -53 mm
X = -17 mm

26. 26
Pile Details:
Pile Size : 250 x 250 mm RC Pile
Pile Spacing : 3 x Pile Dim. (750 mm)
Pile Working Load : 175 kN
N = Total Column Service Load (Incl. self wt. of Pile
Cap 610 Kn)
n = Single Pile Working Load (175 kN)
N/n Ratio = 3.5
PILE ECCENTRICITY CHECK

27. 27
Position of pile without eccentricity
pile 1 pile 2 pile 3 pile 4
x coor -375 375 -375 375
y coor 375 375 -375 -375
Position of pile with eccentricity
pile 1 pile 2 pile 3 pile 4
x coor -403 476 -472 358
y coor 408 452 -292 -428
Pile Group Centroid before pile ecc
A Y AY A X AX
P1 62500.0 375 23437500 62500.0 -375 -23437500
P2 62500.0 375 23437500 62500.0 375 23437500
P3 62500.0 -375 -23437500 62500.0 -375 -23437500
P4 62500.0 -375 -23437500 62500.0 375 23437500
Total 250000 0 250000 0
Centroid Y = 0.00 mm Centroid X = 0.00 mm
Pile Group Centroid after pile ecc
A Y AY A X AX
P1 62500 408 25500000 62500 -403 -25187500
P2 62500 452 28250000 62500 476 29750000
P3 62500 -292 -18250000 62500 -472 -29500000
P4 62500 -428 -26750000 62500 358 22375000
Total 250000 8750000 250000 -2562500
Centroid Y = 35.00 mm Centroid X = -10.25 mm
PILE ECCENTRICITY CHECK

28. 28
Pile Group Centroid after ecc
(-10.25 mm,+35 mm)
X Axis
YAxis
Mx=21.34kNm
My=6.25kNm
+Ymm
+ X mm
PILE ECCENTRICITY CHECK
(0 mm,0 mm)

29. 29
Iy = 0.74
Ix = 0.63
Pile Group Centroid After Pile Failure (Before Pile Add-On)
ex = -10.25 mm
ey = 35.00 mm
moment due to eccentricity
My = 6.25 kNm
Mx = 21.34 kNm
PILE ECCENTRICITY CHECK

30. 30
Checking for pile
capacity
Fpile 1 =
152.41 - 3.32 - 12.55 = 136.54 KN < 175.0 OK!
Fpile 2 =
152.41 - 4.11 + 14.03 = 142.49 KN < 175.0 OK!
Fpile 3 =
152.41 + 3.90 - 11.00 = 159.51 KN < 175.0 OK!
Fpile 4 =
152.41 + 3.11 + 15.57 = 171.10 KN < 175.0 OK!
609.64 609.64
PILE ECCENTRICITY CHECK

31. 31
Summary:
Note that even though the eccentricity of individual piles P#2 &
P#3 exceeds the norm allowable eccentricity of 75 mm in both
directions, the load distributed to all piles < pile working load
capacity 175 kN !!!
Pile P#1 Y = 33 mm
Net X
ecc
Net Y
ecc
X = -28 mm (mm) (mm)
-41 140
Pile P#2 Y = 77 mm
X = 101 mm
Pile P#3 Y = 83 mm
X = -97 mm
Pile P#4 Y = -53 mm
X = -17 mm
Thus
The Pass/Fail criteria or the integrity
of the pile group should rather be
based on the comparison between
redistributed pile loads (due to net
pile group ecc.) and pile working
loads
PILE ECCENTRICITY CHECK

32. 32
Alternatively
A series of ‘Net Pile Group Eccentricity Limit Charts’
can be generated as a quick & ready reference on site.
It can be readily utilized to check and ascertain the
integrity of individual pile groups based on the
summation or net eccentricity of all piles
PILE ECCENTRICITY CHECK

33. 33
(-41,+140)`
0, 208
208, 0
0, 208
-208, 0
0, -208
208, 0
0, -208
-208, 0
-250
-200
-150
-100
-50
0
50
100
150
200
250
-250 -200 -150 -100 -50 0 50 100 150 200 250
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT
CHART (250mm Square Pile @ 175 kN Working Load)
N/n=3.50
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
PILE ECCENTRICITY CHECK
Net Pile Group Ecc
(-41 mm,+140 mm)

34. 34
If on the other hand the value of Nsls is increased from 610 kN to 656 kN
For N/n = 656 kN / 175 kN = 3.75
From chart, the net pile group ecc. point (-41mm, +140 mm) lies outside the
safe zone for N/n = 3.75……….. KO !!
Therefore need additional pile to reduce load on all piles.
PILE ECCENTRICITY CHECK

35. 35
(-41,+140)`
PILE ECCENTRICITY CHECK
0, 100
100, 0
0, 100
-100, 0
0, -100
100, 0
0, -100
-100, 0
-150
-100
-50
0
50
100
150
-150 -100 -50 0 50 100 150
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT
CHART (250mm Square Pile @ 175 kN Working Load)
N/n=3.75
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)

36. 36
Checking for pile capacity
Fpile 1 =
164.02 - 3.57 - 13.50 = 146.94 KN < 175.0 OK!
Fpile 2 =
164.02 - 4.42 + 15.10 = 153.34 KN < 175.0 OK!
Fpile 3 =
164.02 + 4.20 - 11.84 = 171.65 KN < 175.0 OK!
Fpile 4 =
164.02 + 3.35 + 16.76 = 184.13 KN > 175.0 FAIL!
656.06 656.06
PILE ECCENTRICITY CHECK

37. 37
Referring to the following calculation, the optimum
location of additional pile will be at position (+41 mm, -
140 mm)
Note pile load carrying capacity has been reduced to
148.75 kN (less 15%) due to spacing of piles < 3xpile
dim.
PILE ECCENTRICITY CHECK

38. 38
Pile Group Centroid : ex ey
(after pile failure due to excessive ecc)
(mm) (mm)
-10.25 35.00
Ultimate Column Load = 883
RECOMMENDED NET ADD-ON PILE COORDINATES
Total Service Load (Incl. self wt pilecap) = 656.06
Total Service Load / n = 3.75
Nos of Replacement Pile = 1 X Coord. Y Coord.
Replacent pile position X Coord. Y Coord.
41 -140
REPLACEMENT PILE #1 41 -140
REPLACEMENT PILE #2 0 0
NET COORDINATE 41 -140
Reduction Factor for pile group Efficiency
(%)
15.00
Pile Group Centroid : ex ey
(after replacement pile) (mm) (mm)
0.00 0.00
Reduced Pile Working Load (kN) 148.75
Nos of Replacement Piles required 0.41
PILE ECCENTRICITY CHECK
Recommended Optimum Add-
OnPile Coord. (+41 mm, -140
mm)

39. 39
Moment of inertia (with Add-On pile)
Iy = 0.74
Ix = 0.66
Moment Due to eccentricity
Pile Group Centroid
ex = 0.00
ey = 0.00
moment due to the
eccentricity
My = 0
Mx = 0
PILE LOAD REDISTRIBUTION (with Add-On pile)
Fpile 1 = 131.21 - 0.00 - 0.00 = 131.21 KN < 140 OK!
Fpile 2 = 131.21 - 0.00 + 0.00 = 131.21 KN < 140 OK!
Fpile 3 = 131.21 + 0.00 - 0.00 = 131.21 KN < 140 OK!
Fpile 4 = 131.21 + 0.00 + 0.00 = 131.21 KN < 140 OK!
F Add-On pile RP1 = 131.21 0.00 0.00 = 131.21 KN < 140 OK!
Total 656.06 656.06
PILE ECCENTRICITY CHECK

40. 40
P1, -403, 408
P2, 476, 452
P3, -472, -292
P4, 358, -428
RP#1, 41, -140
-500
-400
-300
-200
-100
0
100
200
300
400
500
-600 -400 -200 0 200 400 600
YCOORDINATE(mm)
X COORDINATE (mm)
4 PILE GROUP: OVERALL PILE LOCATION (INCL. ADD-ON PILE RP1)
P1 P2 P3 P4 RP#1
PILE ECCENTRICITY CHECK

41. 41
Again alternatively
A series of ‘Optimum Position of Add-On Pile Chart’
can be generated as a quick & ready reference on site.
It can be readily utilized to ascertain the optimum
add-on pile location in cases where excessive
eccentricity occur for any particular pile group
PILE ECCENTRICITY CHECK

42. 42
-300
-200
-100
0
100
200
300
-150 -100 -50 0 50 100 150
4 PILE GROUP CENTROID PRIOR TO 'ADD-ON' PILE
4 PILE GROUP: OPTIMUM POSITION OF 'ADD-ON'
SINGLE PILE
250 mm Square RC Pile
ADD-ONPILECOORDINATE
+35mm
-140mm
PILE ECCENTRICITY CHECK
-10.25mm
+41mm

43. Part 3: Pile Failure Check

44. 44
PILE FAILURE CHECK
+Ymm
+ X mm
Pile P#1 Y = Fail
Net X
ecc
Net Y
ecc
X = Fail (mm) (mm)
-13 107
Pile P#2 Y = 77 mm
X = 101 mm
Pile P#3 Y = 83 mm
X = -97 mm
Pile P#4 Y = -53 mm
X = -17 mm

45. 45
PILE FAILURE CHECK
Pile Details:
Pile Size : 250 x 250 mm RC Pile
Pile Spacing : 3 x Pile Dim. (750 mm)
Pile Working Load : 175 kN
N = Total Column Service Load (Incl. self wt. of Pile
Cap 610 Kn)
n = Single Pile Working Load (175 kN)
N/n Ratio = 3.5

46. 46
LOAD DETAILS
Ultimate Axial Load kN 818.00
Calculated Self Weight of Pile Cap kN 25.35
Net Service Load kN 609.64
Nos of Piles Required 3.48 4
Pile P#1 y = 1000
x = 1000
Pile P#2 y = 77
x = 101
Pile P#3 y = 83
x = -97
Pile P#4 y = -53
x = -17
NET Y COORDINATE (After Pile Failure) 107
NET X COORDINATE (After Pile Failure) -13
Ultimate Column Load = 818.0
Total Service Load (Incl. self wt pilecap) = 609.64
Total Service Load / n = 3.48
PILE FAILURE CHECK

47. 47
Position of pile without eccentricity
pile 1 pile 2 pile 3 pile 4
x coor -375 375 -375 375
y coor 375 375 -375 -375
Position of pile with eccentricity
pile 1 pile 2 pile 3 pile 4
x coor FAIL 476 -472 358
y coor FAIL 452 -292 -428
Centroid before pile ecc/pile failure
A Y AY A X AX
P1 62500.0 375 23437500 62500.0 -375 -23437500
P2 62500.0 375 23437500 62500.0 375 23437500
P3 62500.0 -375 -23437500 62500.0 -375 -23437500
P4 62500.0 -375 -23437500 62500.0 375 23437500
Total 250000 0 250000 0
Centroid Y = 0.00 mm Centroid X = 0.00 mm
Centroid after pile ecc/pile failure
A Y AY A X AX
P1 FAIL FAIL FAIL FAIL FAIL FAIL
P2 62500 452 28250000 62500 476 29750000
P3 62500 -292 -18250000 62500 -472 -29500000
P4 62500 -428 -26750000 62500 358 22375000
Total 187500 -16750000 187500 22625000
Centroid Y = -89.33 mm Centroid X = 120.67 mm
PILE FAILURE CHECK

48. 48
Moment of inertia with
pile eccentricity
Iy = 0.53
Ix = 0.45
Pile Group Centroid After Pile Failure (Before Pile Add-
On/Pile Replacement)
ex = 120.67
ey = -89.33
moment due to eccentricity
My = -73.56
Mx = -54.46
Checking for pile capacity
Fpile 1 =
FAIL - FAIL - FAIL = FAIL KN > 175.0 FAIL!
Fpile 2 =
203.21 - -48.96 + -65.69 = 219.94 KN > 175.0 FAIL!
Fpile 3 =
203.21 + -81.67 - -24.59 = 260.29 KN > 175.0 FAIL!
Fpile 4 =
203.21 + -32.70 + -41.10 = 129.41 KN < 175.0 OK!
609.64 609.64
PILE FAILURE CHECK

49. 49
PILE ADD-ON/PILE REPLACEMENT PROCEDURE
Pile Group Centroid : ex ey
(after pile failure & before replacement pile)
(mm) (mm)
120.67 -89.33
Ultimate Column Load = 818
RECOMMENDED NET REPLACEMENT PILE
COORDINATES
Total Service Load (Incl. self wt pilecap) = 609.64
Total Service Load / n = 3.48
Nos of Replacement Pile = 2 X Coord. Y Coord.
Replacent pile position X Coord. Y Coord.
-362 268
REPLACEMENT PILE #1 -362 0
REPLACEMENT PILE #2 0 268
NET COORDINATE -362 268
Reduction Factor for pile group
Efficiency (%)
15.00
Pile Group Centroid : ex ey
(after replacement pile) (mm) (mm)
0.00 0.00
Reduced Pile Working Load (kN) 148.75
Nos of Replacement Piles required 1.10
PILE FAILURE CHECK
Recommended Optimum Replacement
Pile Coord. (-362 mm, +268 mm)

50. 50
Position of pile with eccentricity
(With Replacement Pile)
coor pile 1 pile 2 pile 3 pile 4 Rep. PILE #1 Rep. PILE #2
x FAIL 476 -472 358 -362 0
y FAIL 452 -292 -428 0 268
Centroid With Replacement Pile
A Y AY A X AX
P1 FAIL FAIL FAIL FAIL FAIL FAIL
P2 62500 452 28250000 62500 476 29750000
P3 62500 -292 -18250000 62500 -472 -29500000
P4 62500 -428 -26750000 62500 358 22375000
REPLACEMENT PILE #1 62500 0 0 62500 -362 -22625000
REPLACEMENT PILE #2 62500 268 16750000 62500 0 0
Total
312500 0 312500 0
Centroid Y
= 0.00 mm
Centroid X
= 0.00 mm
PILE FAILURE CHECK

51. 51
Moment of inertia (with replacement pile)
Iy = 0.71
Ix = 0.54
Moment Due to eccentricity
Pile Group Centroid
ex = 0.00
ey = 0.00
moment due to the eccentricity
My = 0
Mx = 0
PILE LOAD REDISTRIBUTION (with Add-On/Replacement Pile)
Fpile 1 = FAIL - FAIL - FAIL = FAIL
Fpile 2 = 121.93 - 0.00 + 0.00 = 121.93
Fpile 3 = 121.93 + 0.00 - 0.00 = 121.93
Fpile 4 = 121.93 + 0.00 + 0.00 = 121.93
F replacement pile RP1 = 121.93 0.00 0.00 = 121.93
F replacement pile RP2 121.93 0.00 0.00 = 121.93
Total 609.64 609.64
PILE FAILURE CHECK

52. 52
P1, -375, 325 P2, 375, 325
P3, -375, -375
P4, 375, -425
RP#1, 0, 375
RP#2, -375, 0
-500
-400
-300
-200
-100
0
100
200
300
400
500
-500 -400 -300 -200 -100 0 100 200 300 400 500
YCOORDINATE(mm)
X COORDINATE (mm)
4 PILE GROUP: OVERALL PILE LOCATION
FAILED PILE
REPLACEMENT PILE
REPLACEMENT PILE
PILE FAILURE CHECK

53. 53
Again alternatively
A series of ‘Optimum Position of Replacement Pile
Chart’ can be generated as a quick & ready reference
on site. It can be readily utilized to ascertain the
optimum replacement pile location in cases where pile
failure occur for any particular pile within the pile
group
PILE FAILURE CHECK

54. 54
PILE FAILURE CHECK
-375
-450
-300
-225
-150
-75
375
300
225
150
75
450
-500
-400
-300
-200
-100
0
100
200
300
400
500
-300 -200 -100 0 100 200 300
4 PILE GROUP: OPTIMUM NET COORDINATES OF
REPLACEMENTPILE RP1 & RP2 (PILE FAILURE @ P#1)
OPTIMUM X@P1 FAIL OPTIMUM Y @P1 FAIL
REPLACEMENTPILECOORDINATE
NET ECCENTRICITY OF PILE GROUP (BEFORE PILE REPLACEMENT)
-13mm
-362mm
+107mm
+268mm

55. PART 4: PILE SPACING FACTOR
(K FACTOR)

56. 56
K FACTOR
The spacing of pile centre to centre or the
K Factor also has a direct impact to the
permissible net pile group eccentricity
limit.

57. 57
0, 208
208, 0
0, 208
-208, 0
0, -208
208, 0
0, -208
-208, 0
0, 240
240, 0
0, 240
-240, 0
0, -240
240, 0
0, -240
-240, 0
-250
-200
-150
-100
-50
0
50
100
150
200
250
-250 -200 -150 -100 -50 0 50 100 150 200 250
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT CHART (250mm Square Pile @
175 kN Working Load and with a N/n Ratio=3.5)
k=3.0 k=3.50
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
K=Pile Spacing
K FACTOR

58. PART 5: CONCLUSION &
RECOMMENDATION

59. 59
CONCLUSION
1.0 This study has shown that the norm of
adopting an eccentricity limit of 75mm
for each individual pile in a pile group
as a ‘Pass-Fail’ criteria irrespective of
pile dimensions, intensity of column
service load, pile working load and pile
spacing is unsatisfactory (see pg 32).

60. 60
Pile
P#1 Y = 33 mm
Net X
ecc
Net Y
ecc
X = -28 mm (mm) (mm)
-41 140
Pile
P#2 Y = 77 mm
X = 101 mm
Pile
P#3 Y = 83 mm
X = -97 mm
Pile
P#4 Y = -53 mm
X = -17 mm
Checking for pile
capacity
Fpile 1 =
152.41 - 3.32 - 12.55 = 136.54 KN < 175.0 OK!
Fpile 2 =
152.41 - 4.11 + 14.03 = 142.49 KN < 175.0 OK!
Fpile 3 =
152.41 + 3.90 - 11.00 = 159.51 KN < 175.0 OK!
Fpile 4 =
152.41 + 3.11 + 15.57 = 171.10 KN < 175.0 OK!
609.64 609.64
CONCLUSION

61. 61
2.0 The intensity of column service loads has a
direct impact to the permissible net pile group
eccentricity limit.
CONCLUSION

62. 62
0, 420
420, 0
0, 420
-420, 0
0, -420
420, 0
0, -420
-420, 0
0, 268
268, 0
0, 268
-268, 0
0, -268
268, 0
0, -268
-268, 0
0, 136
136, 0
0, 136
-136, 0
0, -136
136, 0
0, -136
-136, 0
-500
-400
-300
-200
-100
0
100
200
300
400
500
-500 -400 -300 -200 -100 0 100 200 300 400 500
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT
CHART (250mm Square Pile @ 175 kN Working Load)
N/n=3.25 N/n=3.50 N/n=3.75
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
Nult 760 kN Nult 818 kN Nult 883 kN
(N/n=3.25) (N/n=3.5) (N/n=3.75)
X ecc Y ecc X ecc Y ecc X ecc Y ecc
0 340 0 208 0 100
170 170 104 104 50 50
340 0 208 0 100 0
0 340 0 208 0 100
-170 170 -104 104 -50 50
-340 0 -208 0 -100 0
0 -340 0 -208 0 -100
170 -170 104 -104 50 -50
340 0 208 0 100 0
0 -340 0 -208 0 -100
-170 -170 -104 -104 -50 -50
-340 0 -208 0 -100 0
N=Column Service Load kN
n=Pile Working Load kN
CONCLUSION

63. 63
3.0 The spacing of pile centre to centre also has
a direct impact to the permissible net pile
group eccentricity limit.
CONCLUSION

64. 64
0, 208
208, 0
0, 208
-208, 0
0, -208
208, 0
0, -208
-208, 0
0, 240
240, 0
0, 240
-240, 0
0, -240
240, 0
0, -240
-240, 0
-250
-200
-150
-100
-50
0
50
100
150
200
250
-250 -200 -150 -100 -50 0 50 100 150 200 250
4 PILE GROUP : NET PILE GROUP ECCENTRICITY LIMIT CHART
(250mm Square Pile @ 175 kN Working Load)
k=3.0 k=3.50
Eccentricity(+Ymm)
Eccentricity (-X mm)
Eccentricity(-Ymm)
Eccentricity (+X mm)
Nult 818 kN Nult 818 kN
(K=3.0) (K3.50)
X ecc Y ecc X ecc Y ecc
0 208 0 240
104 104 120 120
208 0 240 0
0 208 0 240
-104 104 -120 120
-208 0 -240 0
0 -208 0 -240
104 -104 120 -120
208 0 240 0
0 -208 0 -240
-104 -104 -120 -120
-208 0 -240 0
K=Pile Spacing
CONCLUSION

65. 65
4.0 For pile failure during driving, the required
number of Replacement Pile/s & the
location/coordinate of these piles can be
evaluated.
CONCLUSION

66. 66
PILE ADD-ON/PILE REPLACEMENT PROCEDURE
Pile Group Centroid : ex ey
(after pile failure & before replacement pile)
(mm) (mm)
120.67 -89.33
Ultimate Column Load = 818
RECOMMENDED NET REPLACEMENT PILE
COORDINATES
Total Service Load (Incl. self wt pilecap) = 609.64
Total Service Load / n = 3.48
Nos of Replacement Pile = 2 X Coord. Y Coord.
Replacent pile position X Coord. Y Coord.
-362 268
REPLACEMENT PILE #1 -362 0
REPLACEMENT PILE #2 0 268
NET COORDINATE -362 268
Reduction Factor for pile group
Efficiency (%)
15.00
Pile Group Centroid : ex ey
(after replacement pile) (mm) (mm)
0.00 0.00
Reduced Pile Working Load (kN) 148.75
Nos of Replacement Piles required 1.10
CONCLUSION

67. 67
P1, -375, 375
P2, 476, 452
P3, -472, -292
P4, 358, -428
RP#1, -362, 0
RP#2, 0, 268
-500
-400
-300
-200
-100
0
100
200
300
400
500
-600 -400 -200 0 200 400 600
YCOORDINATE(mm)
X COORDINATE (mm)
4 PILE GROUP: OVERALL PILE LOCATION (INCL. RP1 & RP2)
P1 P2 P3 P4 RP#1 RP#2
CONCLUSION

68. 68
-375
-450
-300
-225
-150
-75
375
300
225
150
75
450
-500
-400
-300
-200
-100
0
100
200
300
400
500
-300 -200 -100 0 100 200 300
4 PILE GROUP: OPTIMUM NET COORDINATES OF
REPLACEMENTPILE RP1 & RP2 (PILE FAILURE @ P#1)
OPTIMUM X@P1 FAIL OPTIMUM Y @P1 FAIL
REPLACEMENTPILECOORDINATE
NET ECCENTRICITY OF PILE GROUP (BEFORE PILE REPLACEMENT)
-13mm
-362mm
+107mm
+268mm
CONCLUSION

69. 69
RECOMMENDATION
The ‘Pass-Fail’ criteria for a particular Pile Group
Arrangement should be based on the comparison between
Redistributed Loads (individual pile) and the Pile Safe Working
Load. These redistributed loads arise from eccentric moments
induced into the pile group due to either pile eccentricity or pile
failure conditions.
> Pile Safe Working Load
Fp: Redistributed Loads to each individual pile kN
N : Net Column Service Load kN (incl self weight of pile cap)
n : Pile Safe Working Load kN

70. 70
RECOMMENDATION
This criteria can then be translated into graphical form for a
specific value of:
i. Pile dimensions
ii. Pile spacing
iii. Pile working loads
iv. Range of column service loads
0, 420
420, 0
0, 420
-420, 0
0, -420
420, 0
0, -420
-420, 0
0, 268
268, 0
0, 268
-268, 0
0, -268
268, 0
0, -268
-268, 0
0, 136
136, 0
0, 136
-136, 0
0, -136
136, 0
0, -136
-136, 0
-500
-400
-300
-200
-100
0
100
200
300
400
500
-600 -400 -200 0 200 400 600
4 PILE GROUP : NET PILE GROUP ECCENTRICITY
LIMIT CHART (250mm Square Pile @ 175 kN Working
Load)
N/n=3.25 N/n=3.50 N/n=3.75
Eccentricity(+Y
mm)
Eccentricity (-X mm)
Eccentricity(-Y
mm)
Eccentricity (+X mm)

71. APPENDIX: Example of 4 Pile
Group Excel Sheet

72. 72
PILE DETAILS
Pile Size mm 250.0
Pile Working Load (kN) 175.0
PILE CAP DETAILS
Pile Spacing K Factor (3 to 5) 3.00 B mm 1300.0
Calculated Pile Cap Overall Depth mm 600.0 600 W mm 1300.0
Minimum Setback Pile Edge mm 150.0 150 H mm 600.0
Cover mm 100.0
LOAD DETAILS
Ultimate Axial Load kN 818.00
Calculated Self Weight of Pile Cap kN 25.35
Net Service Load kN 609.64
Nos of Piles Required 3.48 4
Pile P#1 y = 1000 mm 0
x = 1000 mm
Pile P#2 y = 77 mm 1
x = 101 mm
Pile P#3 y = 83 mm 1
x = -97 mm
Pile P#4 y = -53 mm 1
x = -17 mm
3
NET Y COORDINATE (After Pile Failure) 107
NET X COORDINATE (After Pile Failure) -13
Ultimate Column Load = 818.0
Total Service Load (Incl. self wt pilecap) = 609.64
Total Service Load / n = 3.48
Position of pile without eccentricity
pile 1 pile 2 pile 3 pile 4
x coor -375 375 -375 375
y coor 375 375 -375 -375
Position of pile with eccentricity
pile 1 pile 2 pile 3 pile 4
x coor FAIL 476 -472 358
y coor FAIL 452 -292 -428
Centroid before pile ecc/pile failure
A Y AY A X AX
P1 62500.0 375 23437500 62500.0 -375 -23437500
P2 62500.0 375 23437500 62500.0 375 23437500
P3 62500.0 -375 -23437500 62500.0 -375 -23437500
P4 62500.0 -375 -23437500 62500.0 375 23437500
Total 250000 0 250000 0
Centroid Y = 0.00 mm Centroid X = 0.00 mm
APPENDIX

73. 73
Centroid after pile ecc/pile failure
Iy Ix
A Y AY A X AX
P1 FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL
P2 62500 452 28250000 62500
476
29750000 126261.7778 293041.7778
P3 62500 -292 -18250000 62500
-472
-29500000 351253.7778 41073.77778
P4 62500 -428 -26750000 62500
358
22375000 56327.11111 114695.1111
Total
187500 -16750000
187500 22625000
533842.6667 448810.6667
Centroid Y =
-89.33
mm Centroid X =
120.67
mm
Moment of inertia with pile eccentricity
Iy =
0.53
Ix =
0.45
Pile Group Centroid After Pile Failure (Before Pile Add-On/Pile Replacement)
ex = 120.67
ey = -89.33
moment due to eccentricity
My = -73.56
Mx = -54.46
Checking for pile capacity
F =
Fpile 1 =
FAIL - FAIL - FAIL = FAIL KN > 175.0 FAIL!
Fpile 2 =
203.21 - -48.96 + -65.69 = 219.94 KN > 175.0 FAIL!
Fpile 3 =
203.21 + -81.67 - -24.59 = 260.29 KN > 175.0 FAIL!
Fpile 4 =
203.21 + -32.70 + -41.10 = 129.41 KN < 175.0 OK!
609.64 609.64
APPENDIX

74. 74
PILE ADD-ON/PILE REPLACEMENT PROCEDURE
Pile Group Centroid : ex ey
(after pile failure & before replacement pile)
(mm) (mm)
120.67 -89.33
Ultimate Column Load = 818
RECOMMENDED NET REPLACEMENT PILE COORDINATES
Total Service Load (Incl. self wt pilecap) = 609.64
Total Service Load / n = 3.48
Nos of Replacement Pile = 2 X Coord. Y Coord.
Replacent pile position X Coord. Y Coord.
-362 268
REPLACEMENT PILE #1 -362 0
REPLACEMENT PILE #2 0 268
NET COORDINATE -362 268
Reduction Factor for pile group
Efficiency (%)
15.00
Pile Group Centroid : ex ey
(after replacement pile) (mm) (mm)
0.00 0.00
Reduced Pile Working Load (kN) 148.75
Nos of Replacement Piles required 1.10
Position of pile with eccentricity
(With Replacement Pile)
coor pile 1 pile 2 pile 3 pile 4 Rep. PILE #1 Rep. PILE #2
x FAIL 476 -472 358 -362 0
y FAIL 452 -292 -428 0 268
Centroid With Replacement Pile
A Y AY A X AX Iy Ix
P1 FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL
P2 62500 452 28250000 62500 476 29750000 226576 204304
P3 62500 -292 -18250000 62500 -472 -29500000 222784 85264
P4 62500 -428 -26750000 62500 358 22375000 128164 183184
REPLACEMENT PILE #1 62500 0 0 62500 -362 -22625000 131044 0
REPLACEMENT PILE #2 62500 268 16750000 62500 0 0 0 71824
Total 312500 0 312500 0
Centroid Y = 0.00 mm Centroid X = 0.00 mm 708568 544576
Moment of inertia (with replacement pile)
Iy = 0.71
Ix = 0.54
Moment Due to eccentricity
Pile Group Centroid
ex = 0.00
ey = 0.00
moment due to the eccentricity
My = 0
Mx = 0
PILE LOAD REDISTRIBUTION (with Add-On/Replacement Pile)
F =
Fpile 1 = FAIL - FAIL - FAIL = FAIL KN > 140 FAIL!
Fpile 2 = 121.93 - 0.00 + 0.00 = 121.93 KN < 140 OK!
Fpile 3 = 121.93 + 0.00 - 0.00 = 121.93 KN < 140 OK!
Fpile 4 = 121.93 + 0.00 + 0.00 = 121.93 KN < 140 OK!
F replacement pile RP1 = 121.93 0.00 0.00 = 121.93 KN < 140 OK!
F replacement pile RP2 121.93 0.00 0.00 = 121.93 KN < 140 OK!
Total 609.64 609.64
APPENDIX

75. FORENSIC CIVIL ENGINEERING SEMINAR
ForCES ’18
29th & 30th Oct. 2018 utm kuala lumpur
THANK YOU
MAY 2017