CHAPTER 5
RESULT AND ANALYSIS
5.1
Introduction
For analysis purpose, the relevant data and test results are collected from six
selected sites. The data and test results are obtained from the soil investigation, pile
driving records and pile load test results on site. Besides, all the data are also from
the same source. Thus, for a particular site, the driving record used in pile driving
formula should be from the same pile that selected for load testing. Also, the
designed pile length in static analysis should be same as the driven length that
obtained from the driving record. Ultimate capacity of a pile was calculated based
on the method selected as mentioned in Chapter four, which are Meyerhof’s Method
for static analysis, Modified Engineering News Record (ENR) Formula, Hiley
Formula and Gates Formula for pile driving formula and Professor Chin’s Method
for interpretation of the load test result.
For comparison purpose, summary of the ultimate capacity for the entire site
are presented in table form, which the ultimate capacities that obtained from different
methods are compared to each other and the differences in percentages are
established. Finally, the analysis results are presented in bar chart form for
convenient reading.
63
5.2
Calculations Example
For easy understanding purpose, a calculation example for each of those
selected methods that showing all the detail steps in obtaining the ultimate capacities
are attached.
5.2.1
Static Analysis
5.2.1.1 Calculation Example – Meyerhof’s Method
Project 4:
From Equation 3.1:
Ultimate pile capacity, Qult = Qs + Qb
Nominal surface area of the pile in soil layer, As = 2j x L
= 2  (0.35/2) x L
= 1.1 L m2
Frictional Resistance, Qs
350 mm  spun pile
64
Assumption 1:
Skin friction is mobilized to the whole length of the driven pile.
For 0 – 10.2 m,
Cu = 18.67 Kpa,
From Figure 3.4:  = 1.179
From Equation 3.13 :
Qs = ƒp L
= 18.67 x 1.179 x 1.1 x 10.2
= 247.05 KN
For 10.2 – 29.60 m,
Cu = 23.44 Kpa,
From Figure 3.4:  = 1.07
From Equation 3.13 :
Qs = ƒp L
= 23.44 x 1.07 x 1.1 x 19.4
= 535.22 KN
For 29.6 – 35.0 m,
Take N avg = 8,
Cu = correlation factor x N
= 6.67 x 8 = 53.36 kPa
From Figure 3.4:  = 0.825
From Equation 3.13 :
Qs = ƒp L
= 53.36 x 0.825 x 1.1 x 5.4
= 261.49 KN
For 35.0 – 43.1 m,
Take N avg = 12,
Cu = correlation factor x N
= 6.67 x 12 = 80.04 kPa
From Figure 3.4:  = 0.6
From Equation 3.13 :
Qs = ƒpL
= 80.04 x 0.6 x 1.1 x 8.1
= 427.89 KN
65
For 43.1 – 48.9 m,
Take N avg = 15,
Cu = correlation factor x N
= 6.67 x 15 = 100.05 kPa
From Figure 3.4:  = 0.5
From Equation 3.13 :
Qs = ƒp L
= 100.05 x 0.5 x 1.1 x 5.8
= 319.16 KN
For 48.9 – 52.42 m,
The soil is silty sand, therefore from the SPT test,
The SPT N-value = 60.75, N’ = 0.6 x 60.75
= 36.45
cu = 2N’ = 72.90
From Equation 3.13 :
Qs = ƒpL
= 72.90 x 1.1 x 2.52
= 282.27 KN
Assumed bedding level, RL= - 52.42 m
Ap =  j2
=  (0.35/2)2
= 0.096 m2
The soil is dense sand, N = 65.22, therefore, N' = 65.22 x 0.6 = 39.13
bu = 40N’ x Db/B
= 40 x 39.13 (1/0.35)
= 4471.97 KN
< 400N’ = 13200  ok.
Pbu = Apbu
= 0.096 x 4471.97
= 429.31 KN
66
From Equation 3.1:
Ultimate pile capacity, Qult = Qs + Qb
Qult = 247.05 + 535.22 + 261.49 + 427.89 + 319.16 + 282.27 + 429.31
= 2502.39 KN
Assumption 2:
Skin friction mobilized only in the stiff layers
Skin friction lost from 0 – 23 m,
= Qs(0-8) + (12.8 x 2πj x α x Cu)
= 247.05 + (23.44 x 1.07 x 1.1 x 12.8)
= 600.19 KN
Remaining ultimate pile capacity = 2502.39 – 600.19
= 1902.2 KN
* The calculation for the correlation factor is attached in Appendix H.
* The depth of down drag in the soil is determine by the software named CONSOL
(a special software to determine the consolidation and rate of consolidate).
5.2.1.2 Summary Of Ultimate Capacity From Static Analysis
On the basis of the comparison of ultimate capacity using the static analysis
and in situ testing, it is proposed to use the assumption two, thus Skin friction
mobilized only in the stiff layers, to achieve a practical results. The results of
ultimate capacity for all the six selected sites are summarized in Table 5.1 below
showing, while the breakdown of skin friction and end bearing capacity value are
attached in Appendix I-1 to I-6 for reference.
67
Table 5.1: Summary of ultimate capacity from static analysis
Project Name
5.2.2
Ultimate Capacity, Qu (KN)
Project 1
1450.38
Project 2
1651.57
Project 3
1656.54
Project 4
1902.20
Project 5
1335.07
Project 6
1648.22
Pile Driving Formula
Three driving formulas were chosen in this study, thus Modified ENR
Formula, Hiley Formula and Gates Formula. The ultimate capacity are calculated
based on the driving records on site and calculation example for each of those
formula used are showing in the following part. The ultimate capacity for every
selected site that obtained from the three mentioned methods is summarized in Table
5.2 for comparison purpose. While summary of driving record and calculation steps
for the three formulas for all the selected sites are attached in Appendix J to O-3.
5.2.2.1 Modified ENR Formula
Project 4:
Pile No
Pile Size
Hammer
: BP1
: 350 mm Diameter
: K-25
68
Table 3.2
Table 3.3
Appendix P
Appendix J
(
:
:
:
:
Hammer efficiency, E
Coefficient of restitution, n
Weight of ram, WR
Pile Length, L
Penetration of pile per hammer blow, S
= 0.8
= 0.5
= 24.5 KN
= 52.42 m
= 0.008 m
Solution:
From Modified ENR formula:
Qu =
EWRh WR + n2WP
S + C WR + WP
From the Standard Products Properties (Appendix Q),
Nominal weight of 350mm diameter Spun pile = 160 kg/m
= 1.5696 KN/m
The pile weight = 1.5696 KN/m * L
= 1.5696 * 52.42
= 82.278 KN
+
From
Table D.5 in Appendix P, for diesel hammer,
Weight of ram, WR = 24.5 KN
Height of hammer drop, h = 1.5 m
WRh = 24.5 * 1.5 = 36.75 KNm
Therefore,
Qu
=
(0.8)(36.75)
0.008 + 0.0254
24.5 + (0.5)2 (82.278)
24.5 + 82.278
= 880.24 * 0.4221
= 371.54 KN
5.2.2.2 Hiley Formula
Table 3.2
Table 3.3
: Hammer efficiency, eh
: Coefficient of restitution, n
= 0.8
= 0.5
Appendix P
: Weight of ram, Wr
= 24.5
KN
69
Appendix J
: Pile Length, L
Penetration of pile per hammer blow, s
= 52.42 m
= 0.008 m
Solution:
From Hiley formula:
eh Eh
Qu = s + 1/2 (c1 + c2 + c3)
Wr + n2 Wp
W r + Wp
From the Standard Products Properties given (Appendix Q),
Nominal weight of 350mm dia. Spun pile = 160 kg/m
= 1.5696 KN/m
The pile weight = 1.5696 KN/m * L
= 1.5696 * 52.42
= 82.278 KN
From Table D.5 in Appendix P, for diesel hammer,
Weight of ram, Wr =
Height of hammer drop, h
24.5 KN
= 1.5 m
WRh = 24.5 * 1.5 =
36.75 KNm
From Table 3.4 - Manufacturer Printed Manual,
The driving on site is in the category of Medium Driving - 0.006 'l'
Cap compression, c1 = 0.10 inch = 0.00254 m
Length of pile = 52.42 m = 171.94 ft
0.006 'l' = 0.006 (171.94)
= 1.0316
Pile compression, c2 =1.0316 inch = 0.02620 m
Ground compression, c3 = 0.15 inch = 0.00381 m
Therefore,
Qu
=
(0.8)(36.75)
0.008 + 1/2 (0.03255)
= 1211 * 0.4221
= 511.16 KN
24.5 + (0.5)2 (82.278)
24.5 + 82.278
70
5.2.2.3 Gates Formula
Solution:
From Gates formula:
Qu = a √[EHE ] (b – log S)
Qu is in KN, therefore a = 104.5, b = 2.4 and E = 0.85 for diesel hammer
From Table D.5 in Appendix P, for diesel hammer,
Weight of ram, Wr = 24.5 KN
Height of hammer drop, h = 1.5 m
Rated hammer energy = WRh = 24.5 * 1.5 =
36.75 KNm
From Appendix J,
Penetration of pile per hammer blow, s =
mm
8
Therefore,
Qu = a √[EHE ] (b – log S)
= 104.5 √[0.85 * 36.75 ] (2.4 – log 8)
= 874.27 KN
5.2.2.4 Comparison Of Ultimate Capacity From Pile Driving Formulas
Table 5.2: Summary of ultimate capacity from pile driving formulas
QU FROM PILE DRIVING FORMULAS (KN)
Project Name
Modified ENR
Hiley
Diff. (%)
Gates
Diff. (%)
Project 1
243.03
322.49
32.70
575.29
136.72
Project 2
232.04
259.39
11.79
595.61
156.69
Project 3
364.73
485.80
33.19
874.27
139.70
Project 4
371.54
511.16
37.58
874.27
135.31
Project 5
354.70
486.74
37.23
817.67
130.53
Project 6
268.15
334.70
24.82
629.49
134.75
71
Comparison Of Ultimate Capacity Based On
Different Pile Driving Formulas
1000
900
800
Ultimate Capacity, Qu (KN)
700
600
500
400
300
200
100
0
Project 1
Project 2
Project 3
Project 4
Project 5
Project 6
Selected Project
Modified ENR
Hiley
Gates
Figure 5.1: Comparison of ultimate capacity from pile driving formulas
72
Three pile driving formulas using momentum conservation is considered in
this study, i.e. Modified ENR Formula, Hiley Formula and Gates Formula. The type
of soil that dominated in the selected sites is clayey soil. For this type of soil, it is
found that the ultimate capacity obtained from the Modified ENR Formula gives the
lowest value among the three formulas while Gates formula shows the highest value
of ultimate capacity. In most cases, the ultimate capacities from Hiley Formula are
30% to 40% higher than the Modified ENR Formula. While the ultimate capacities
from Gates Formula show a different around 1.3 times higher than the Modified
ENR Formula.
The concept for Modified ENR method and Hiley method is almost the same,
which both of it consider the factor of hammer efficiency, pile weight, average
penetration per hammer blow and also coefficient of restitution between the ram and
the pile capacity. It is found that the differences in value of the ultimate capacity of
these two formulas very much depend on the temporary compression. In Modified
ENR Formula, C is equal to 0.0254 mm. Where as in Hiley Formula, a more
conservative value is computes from c1, c2 and c3. It is essentially to say that Hiley
method is to be more reliable as compared to Modified ENR Formula as it has
concern about the relationship between the pile and the driven ground condition
during the driving process. Where it looks into the type of driving, thus medium
driving, hard driving or very hard driving as well as the temporary compression that
occur during driving process, which including cap compression, pile compression
and ground compression.
All the pile driving formulas except the Gates Formula are derived using
various assumptions. The assumption usually depends on personal experiences and
it may couple with wide variability of soils and hammer conditions. As for Gates
Formula, it is a more simplify equation to be used and it is not really subjected to
variation due to the compression effect and all the coefficient of restitution. It is
therefore, the ultimate value from Gates Formula to be higher from the other two
formulas.
73
5.2.3
Pile Load Test - Chin’s Method
5.2.3.1 Example Calculation
Project 4
Pile Size : 350 mm Diameter
Hammer : K-25
Table 5.3: Load-settlement relationship of the pile
(For first cycle and minus residual)
LOAD
SETTLEMENT
P
(Ton)
(mm)
0.00
0.00
0.0000
18.75
1.56
0.0832
37.50
3.56
0.0949
56.25
5.45
0.0969
75.00
8.33
0.1111
56.25
7.63
0.1356
MINUS RESIDUAL
37.50
6.94
0.1851
SETTLEMENT
P
18.75
6.03
0.3216
(mm)
0.00
3.53
0.0000
0
18.75
3.82
0.0000
0.29
0.0155
37.50
5.53
0.1475
2.00
0.0533
56.25
6.66
0.1184
3.13
0.0556
75.00
8.71
0.1161
5.18
0.0691
93.75
10.15
0.1083
6.62
0.0706
112.50
12.22
0.1086
8.69
0.0772
131.25
14.36
0.1094
10.83
0.0825
150.00
18.00
0.1200
14.47
0.0965
131.25
18.54
0.1413
112.50
16.93
0.1505
93.75
15.41
0.1644
75.00
13.26
0.1768
56.25
11.65
0.2071
37.50
10.33
0.2755
18.75
7.49
0.3995
0.00
4.83
0.0000
5.2.3.2 Interpretation Of Load Test Result By Chin’s Method – Stability Plot
Stability Plot For Spun Pile at BP1, Project 4
(Chin's Method)
Settlement (mm)
0
2
4
6
8
10
12
14
16
18
20
0.12
/P (mm/Ton)
0.10
0.08
0.06
0.04
0.02
0.00
First Cycle
Linear (First Cycle)
Minus Residual
74
Figure 5.2: Stability plot
75
5.2.3.3 Estimation Of Ultimate Pile Capacity From Stability Plot
From the stability plot,
For 1st Cycle:
Slope of the plot = (0.1111 - 0.0832) / (8.33 - 1.56)
= 0.0279 / 6.77
= 0.0041 ton-1
Know that the inverse slop of the plot gives the ultimate capacity,
Thus,
Ultimate Capacity of the pile, Qult = 1/ 0.004 ton-1
= 242.652 ton
= 2426.52 KN
For Minus Residual:
Slope of the plot = (0.0965 - 0.0535) / (14.5 - 2)
= 0.0430 / 12.5
= 0.0034 ton-1
Know that the inverse slop of the plot gives the ultimate capacity,
Thus,
Ultimate Capacity of the pile, Qult = 1/ 0.003 ton-1
= 290.698 ton
= 2906.98 KN
From the load test results, it is found that the head settlement for first cycle
and second cycle of spun piles is quiet near to each other. For example, from Table
5.3 above, the residual settlement after the first cycle is 3.53 mm. Which as for
second cycle, the residual settlement is 4.83 mm. The difference is considered very
small and exhibited similar initial residual strengths. In this condition, it is reasonable
to say that the driven pile has achieved its capacity at a constant stage. Hence, the
interpretation of ultimate capacity by using first cycle result is considered reliable.
76
5.2.3.4 Summary Of Ultimate Capacity From Load Test Results
Similar with the example calculation for Project 4, all the ultimate capacities
for the other selected sites are interpret from static load test results that carried out
for that particular pile by using Chin’s Method. The related data, stability plot as
well as the interpretation results are shown in Appendix R-1 to V-3. While the
summary of the ultimate capacity for the six selected sites are shown in Table 5.4
below.
Table 5.4: Summary of ultimate capacity from load test results
Project Name
Ultimate Capacity, Qu (KN)
Project 1
1904.76
Project 2
2285.71
Project 3
2230.77
Project 4
2426.52
Project 5
1818.18
Project 6
2105.26
5.3
Comparison Of Ultimate Pile Capacity, Qu
5.3.1
Comparison Of Ultimate Capacity Between Theoretical Formula And In-Situ Testing
Table 5.5 : Summary of ultimate capacity from load test results, pile driving formula and static analysis
ULTIMATE CAPACITY, QU (KN)
Project Name
Pile Driving Formula
Modified ENR
Hiley
Gates
Static Analysis
(Meyerhof's Method)
Project 1
1904.76
243.03
322.49
575.29
1450.38
Project 2
2285.71
232.04
259.39
595.61
1651.57
Project 3
2230.77
364.73
485.80
874.27
1656.54
Project 4
2426.52
371.54
511.16
874.27
1902.20
Project 5
1818.18
354.70
486.74
817.67
1335.07
Project 6
2105.26
268.15
334.70
629.49
1648.22
77
Load Test
(Chin Method)
Ultimate Capacity From Load Test Result, Pile Driving Formulas
And Static Analysis
Ultimate Capacity, Qu (KN)
2500
2000
1500
1000
500
0
1
2
3
4
5
6
Selected Project
Load Test (Chin Method)
Modified ENR
Hiley
Gates
Static Analysis (Meyerhof's Method)
78
Figure 5.3: Ultimate capacity from load test result, pile driving formulas and static analysis
79
From Table 5.5 and Figure 5.3 above, it is found that ultimate capacity
determined from pile load test result show the highest value compare with the other
two methods. This followed by static analysis and pile driving formula respectively.
Ultimate capacity, Qu obtained from Chin’s method is more reliable as it is
determined through the load test where installed pile are load to twice the working
load as desired by the designer. It is always more convincing the designer as the pile
has been loaded and the soil partial at the pile shaft or pile toe has been adequately
mobilized to gain its strength.
As for ultimate capacity obtained from the static analysis and pile driving
formulas, both are lower than the load test results. However, ultimate capacity from
static analysis shown a closer value to ultimate capacity from load test results as it is
based on bearing capacity theory and the soil parameters used in the analysis were
predicted from the borehole data. But pile driving formulas only a prediction of
energy transfer from the hammer drop to the driven pile only. Various empirical
assumptions may not be found satisfactory to correlate to field condition.
5.3.2
Comparison Between Static Analysis And Load Test Results
Table 5.6: Comparison of ultimate pile capacity, Qu from load test results and static analysis
Soil Characteristic
Project
Name
Driving
Depth
Ultimate Capacity (KN)
Comparison
Differences (%)
(m)
Type Of Soil Along
Middle Strata
Type Of Soil At
Bedding Level
Average
SPT-N Value
Static
Analysis
Load Test
Results
Static Analysis vs
Load Test Results
Project 1
46.00
Silty Clay
Silty Sand
16.37
1450.38
1904.76
23.85
Project 2
68.10
Stiff Silty Clay
Stiff Silty Clay
7.38
1651.57
2285.71
27.74
Project 3
55.62
Sandy Silty Clay
Sandy Silty Clay
16.67
1656.54
2230.77
25.74
Project 4
52.42
Silty Clay
Silty Gravelly Sand
21.88
1902.20
2426.52
21.61
Project 5
50.50
Silty Clay
Silty Clay
6.15
1335.07
1818.18
26.57
Project 6
52.00
Soft Silty Clay
Clayey Silty Sand
17.40
1648.22
2105.26
21.71
80
81
Comparison between ultimate capacities from interpretation of load test
results (Chin’s method) and static analysis (Meyerhof’s method) show the
percentages difference ranging from 21.61% to 27.74%.
As stated in “Geotechnical Information Of The Selected Sites” in Chapter 4,
type of soils for the selected sites are silty clay with lamination of sand at certain
layers. In purpose of studying the soils characteristics factor to the differences
between these two methods, few criteria have been highlighted, thus the driving
depth, type of soil along middle strata, type of soil at bedding level as well as
average SPT-N value. As observed in Table 5.6, Project 2 and 5 can be categorized
in a different group from Project 1, 3, 4 and 6. These two projects achieved a lower
value in standard penetration test as well as having the same type of soil at both the
middle strata and bedding level of pile, thus silty clay while the other projects were
bedding on a sand strata. From the table, it is found that ultimate capacity calculated
from static analysis for Project 2 and 5 achieved a lower value when their piles were
bedding on clayey strata, even though they were driven deeper. At the same time, a
higher percentage of differences achieved when compared to the load test results.
As from Meyerhof’s formula, calculation of end bearing capacity in clayey
soil is using equation of 9 Cu Ap while sandy soil is using 40N (Db/B)Ap. It is found
the larger difference was established when the base stratum is of clayey soil where
the clay formula needs to be used. This is because the clay formula for end bearing
capacity in Meyerhof’s Method gave a lower value, which is therefore
underestimated.
CORRELATION CHART
Qu Static Analysis (Meyerhof's Method), KN
2000
1800
1600
y = 0.76 x
1400
1200
1000
800
600
400
200
0
0
250
500
750
1000
1250
1500
1750
2000
2250
2500
Qu Load Test (Chin's Method), KN
82
Figure 5.4: Correlation factor for ultimate capacity from load test result and static analysis
83
The ultimate capacities of the measured and calculated values at the six
selected sites were also used to establish a correlation chart. It is observed that the
ultimate capacity of a pile calculated from static analysis can be correlated to the
ultimate capacity measured from load test on site. It is however consistently smaller
in magnitude with a reduction factor ranging from 1.28 to 1.38. The correlation chart
also illustrates the linear relationship between these two methods, which could be
represented by the equation:
Qu SA = 0.76 Qu LT
Which calculation of ultimate pile capacity in static analysis was using Meyerhof’s
Method while interpretation of load test results was based on Chin’s Method.
Ultimate load from load test, interpreted using Chin’s method is taken as a
datum data to compare with other methods. This is because result from load test is
based on actual loading and actual site condition.
5.3.3
Comparison Between Static Analysis And Pile Driving Formulas
Table 5.7: Comparison of ultimate capacity from static analysis and pile driving formulas
ULTIMATE CAPACITY, QU (KN)
Project Name
Static Analysis
Pile Driving Formulas
(Meyerhof's Method)
Modified ENR
Diff.(%)
Hiley
Diff.(%)
Gates
Diff.(%)
Project 1
1450.38
243.03
83.24
322.49
77.77
575.29
60.34
Project 2
1651.57
232.04
85.95
259.39
84.29
595.61
63.94
Project 3
1656.54
364.73
77.98
485.80
70.67
874.27
47.22
Project 4
1902.20
371.54
80.47
511.16
73.13
874.27
54.04
Project 5
1335.07
354.70
73.43
486.74
63.54
817.67
38.75
Project 6
1648.22
268.15
83.73
334.70
79.69
629.49
61.81
84
COMPARISON OF ULTIMATE CAPACITY BASED ON
STATIC ANALYSIS AND PILE DRIVING FORMULAS
2000
ULTIMATE CAPACITY, Qu (KN)
1750
1500
1250
1000
750
500
250
0
Project 1
Project 2
Project 3
Project 4
Project 5
Project 6
SELECTED PROJECT
Static Analysis (Meyerhof's Method)
Modified ENR Formula
Hiley Formula
Gates Formula
85
Figure 5.5: Comparison of ultimate capacity based on static analysis and pile driving formulas
86
From the comparison between static analysis and pile driving formulas, it is
shown that static analysis by Meyerhof’s method has a higher ultimate capacity, Qu
as compared to the three selected pile driving formulas. While among the three
driving formulas, Gates Formula shows a closer value to static analysis.
Static analysis is based on bearing capacity theory and the soil parameters
were predicted from the borehole data. These are not happening for analysis by pile
driving formulas where its assumptions depends only on types of piling equipment
and its efficiency as well as the slenderness of pile.
Pile driving formulas give the value of ultimate capacity during the driving
process. The values are significantly lower due to the soil that has been remolded
during the driving process especially when involving clayey soils. This can be
observed from the calculated ultimate capacity that using driving formulas in Project
2 always shows the lowest value as compared with other projects even though it
achieved the highest value of driving depth. Besides, Project 2 also indicated a
highest percentage of difference when compared to the value from static analysis.
As described in “Geotechnical Information Of The Selected Sites” in Chapter 4 and
Table 5.4 in previous part, Project 2 obtained the clayey soil at both along the middle
strata and bedding level of pile. As therefore, the significantly lower value and
higher percentage of difference established in Project 2 is because of the remolding
of soil that due to the driving works has created greater disturbance to clayey soil.
5.3.4
Comparison Between Load Test Result And Pile Driving Formulas
Table 5.8 : Comparison of ultimate capacity from load test results and pile driving formulas
ULTIMATE CAPACITY, QU (KN)
Project Name
Load Test Results
Pile Driving Formula
Stability Plot
Modified ENR
Diff.(%)
Hiley
Diff.(%)
Gates
Diff.(%)
Project 1
1904.76
243.03
87.24
322.49
83.07
575.29
69.80
Project 2
2285.71
232.04
89.85
259.39
88.65
595.61
73.94
Project 3
2230.77
364.73
83.65
485.80
78.22
874.27
60.81
Project 4
2426.52
371.54
84.69
511.16
78.93
874.27
63.97
Project 5
1818.18
354.70
80.49
486.74
73.23
817.67
50.03
Project 6
2105.26
268.15
87.26
334.70
84.10
629.49
70.10
87
COMPARISON OF ULTIMATE CAPACITY BASED ON
LOAD TEST RESULT AND PILE DRIVING FORMULAS
2500
ULTIMATE CAPACITY, Qu (KN)
2250
2000
1750
1500
1250
1000
750
500
250
0
Project 1
Project 2
Project 3
Project 4
Project 5
Project 6
SELECTED PROJECT
Load Test Results
Modified ENR Formula
Hiley Formula
Gates Formula
88
Figure 5.6: Comparison of ultimate capacity based on load test result and pile driving formulas
89
From the comparison between load test and pile driving formulas, it is noted
that ultimate capacity from interpretation of load test results by Chin’s method
achieved a 60% to 90% higher value as compare to the three selected pile driving
formulas. As the comparison between static analysis and pile driving formulas, the
ultimate capacity from Gates Formula still shows a closer value from load test result
than the other two methods.
The pile driving formulas are only the prediction of pile capacity to be
achieved during the driving process and significantly affected by the type of piling
equipment but the relationship of pile to the soil properties is not precisely described.
However, the ultimate capacity from these driving formulas would be even lower
when the sites involved more clay layer. This can be observed from the calculated
ultimate capacity of Project 2, which it shown a lowest value as compared with other
projects as well as obtained a highest difference when compared with load test results
even though it achieved the highest value of driving depth. The significant lower
value and higher percentage of difference established in Project 2 may be able to be
explained by the remolding of soil that due to the driving works has created greater
disturbance to clayey soil as compared to sandy soil.
The load test results are more reliable due to the following reasons:

The pile has been driven and loaded,

The actual behavior of pile will be established based on the actual site
condition,

Although it does not pre-determine the pile slenderness, the effect still
will be reflected during the load test.