ISGTI 2018 78 April2018, IIT Delhi, India
Railway Structure Pile Design Comparison Considered with the difference of Japan and India Torajiro Fujiwara East Japan Railway Company, Structural Engineering Center, 226 Shibuya Tokyo, Japan Email: tfujiwara@jreast.co.jp
Lalit Kumar Feedback Infra Private Limited, 15th Floor Tower 9B, DLF cyber city PhaseIII, Gurgaon, Haryana122002 Email: luckysoni.edu@gmail.com
Junya Sawame East Japan Railway Company, Structural Engineering Center, 226 Shibuya Tokyo, Japan Email: sawame@jreast.co.jp
Suguru Ikejima Kyushu Railway Company, Facilities Department, 32521 Hakata Fukuoka, Japan Email: s.ikejima@jrkyushu.co.jp
ABSTRACT: Design and construction of pile foundation for important infrastructure project in every country is an acute issue. In most countries design codes for pile foundation are introduced to enhance the strength and making the construction more economic and viable. Japan also introduced pile foundation design codes and revised it again and again based on lessons learned from field surveys on damaged infrastructure projects. In consequence Japanese current design code realizes fairly good performance which was evidenced by different infrastructure projects currently running at good pace. Among various structure design codes, every country design codes for foundations is decided and judged based on local soil/rock characteristics, environmental conditions, experimental results and actual structures which have been constructed. The present study shows the comparison of design results of Bored Cast Insitu pile by adopting Japanese and Indian Railway foundation codes. The study shall also reveal about the validity of Japanese Railway Structure Foundation Design Code can be adopted for future India projects, considering comparison with geotechnical investigation condition, geological condition, materialsâ€™ difference, and the accuracy of execution between Japan and India. Keywords: Bored Cast Insitu Pile; Japanese Railway Standard, Indian Railway foundation code, Indian code for Pile foundation 1. Introduction Recent years have witnessed Japan, both at the Government as well as at the business and academic levels, displaying an increasing interest in India. A number of initiatives have been taken by the two governments to improve bilateral relations in almost every field. With a view to provide more focus and purpose to science and technology between the two countries. The effort of ongoing planning for establishment of advanced skill development, sharing of technology, industrial cluster for investment and megainfrastructure initiatives India and Japan affirmed the importance of skill development as an important tool for promotion of skills and capacity enhancement of the local youth.
depth. The rationale for selecting the specific standards is directly linked to the key evaluation of standards and, selection of the same for future Indian infrastructure projects (funded by Japanese government). Though pile foundations are widely discussed by many researchers in order to do research of safer and more economic designs for different type of the infrastructure projects during static and dynamic conditions. The factors used to calculate the pile foundation by Japanese standards and Indian standards vary significantly and hence to study the impact of those factor on calculation of pile foundation is very much necessary for this comparative study. The comparison is part of a major research study on the design of pile foundations done by a Japanese company with interests in performance based design and the loading response of piles in reclaimed land. There is different type of pile foundation used internationally. Pile foundation can be categorized based on installation method, forming material, strata in which the pile is supposed to be installed and cross section of pile. The present study reveals the comparison axial pile capacities and different factors, equations used for the design of concrete circular bored cast in situ pile foundation in cohesive and granular soil types.
Therefore, there might be some probability to transfer the Japanese Technology to India in some projects for the future and also to adopt the Japanese Structure Design Code for upcoming new infrastructure projects. So, this study comprises of comparison of Indian codes for pile foundation design and Japanese codes for pile foundation design. 2. The Purpose of this study This study involves the analysis and synthesis of the similarities, differences and patterns across different codes and standards of pile foundation design, which share a common focus or goal. To be able to do this well, the specific factors of each standard has described in
Standard Penetration Test (SPT) is appropriate to estimate the resistance and density of granular soils and also sometime widely used to find out the cohesion properties of soils and is largely practiced in the Japan 1
Railway Structure Pile Design Comparison Considered with the difference of Japan and India
region while designing the foundation of mostly railway projects. In most of railway project in Japan the pile capacity has been derived by using standard penetration (SPT) values; hence for this comparative study the use of SPT values is taken into preference and capacity has been calculated by the codes and standards of both the countries.
n
Qu A p N c C p i ci Asi where: Qu Ultimate load capacity, in kN
Ap crosssectional area of pile tip, in m2 N C bearing capacity factor, may be taken as 9
3.
Comparison of different equations used for design of Pile foundation Every country has different design factor and often equation for the calculation of pile foundation, in present study the factors and equations used for calculation of pile foundation in India and in Japan are summarized below:
C p average cohesion at pile tip, in kN/m2 n
installed and which contribute to positive skin friction i adhesion factor for the ith layer depending on the consistency of soil ci average cohesion for the ith layer, in kN/m2
Asi surface area of pile shaft in the ith layer, in m2
Bearing Capacity equation for granular soil is
Bearing capacity equation based on SPT values for granular soil is:
Qu A p 0.5 DN PD N q K i PDi tan i Asi n
i 1
Qu 13 N
(1)
L length of penetration of pile in bearing strata, in m B diameter or minimum width of pile in m
Ap crosssectional area of pile tip, in m2
effective unit weight of the soil at pile tip, in kN/m3 N bearing capacity factors depending on Nq and can
N average N along the pile shaft As surface area of pile shaft, in m2
N 2N q 1 tan
In no case the end bearing resistance should be more than
PD effective overburden pressure at pile tip, in kN/m
130 NA p
2
N q bearing capacity factor depends on the angle of
For nonplastic silt or very fine sand the above formula should be replaced by the following formula.
internal friction at pile tip
Qu 10 N
summation for layers 1 to n in which pile is
i 1
installed and which contribute to positive skin friction
Ki coefficient
(3)
N average N value at pile tip
2
D diameter of pile shaft, in m
n
N As L Ap B 0.50
Qu Ultimate load capacity, in kN
where: Qu Ultimate load capacity, in kN
be calculated as
summation for layers 1 to n in which pile is
i 1
3.1 From Indian standards and codes As per Indian code of practice (IS 2911 Part1 Section2) the bearing capacity equations are:
Ap crosssectional area of pile tip, in m
(2)
i 1
N As L Ap B 0.60
3.2 From Japanese standards and codes As per Japanese code of practice (Design Standards for Railway Structures and Commentary[Foundation]) the bearing capacity equations are:
of earth pressure applicable for the ith
layer (range from 1.0 to 1.5)
PDi effective overburden pressure for the ith layer, in kN/m2
Rvd f r Rtk R fk
ith layer (may be taken equal to the friction angle of the soil around the pile stem)
R f r pt tk Rk
i angle of wall friction between pile and soil for the Asi surface area of pile shaft in the ith layer, in m2
15 times the diameter of the pile shaft for
30
(5) (6)
Rtk qtk At
To calculate the bearing capacity the by static formula, the maximum effective overburden at the pile tip should correspond to the critical depth, which may be taken as 0
(4)
(7)
R fk r fkU l
and
(8)
q tk 60 N 7500 kN / m (for Granular soil)
(9)
q tk 51N 9000 kN / m (for cohesive soil)
(10)
rtk 1.5 N 75 kN / m (for granular soil)
(11)
2
increasing to 20 times for 40 Bearing Capacity equation for cohesive soil is 0
2
2
2
Railway Structure Pile Design Comparison Considered with the difference of Japan and India
rtk 6 N 75 kN / m 2 (for cohesive soil)
0.3 N 27
(12)
(13)
where: angle of internal friction, degrees
where:
Rvd design bearing load capacity, in kN
N SPT value Relation of SPT with cohesion intercept Even though SPT values are not considered as a good measure of the strength of clays, it is used extensively as a measure of the consistency of clays. The consistency is then related to its approximate strength and then to cohesion intercept
f r ground resistance coefficient depends on p t
Rtk basic tip end bearing resistance
R fk basic shaft friction resistance
Rk total basic bearing resistance Rk Rtk R fk
qu
pt the ratio of basic tip bearing resistance by total
N 8
(14)
qu 2
bearing resistance
c
qtk basic tip end bearing resistance stress, in kN/m2
where: q u undrained strength of soils, in kg/cm2
At crosssectional area of pile tip, in m2
c Cohesion intercept, in kg/cm2
N SPTN value r fk basic skin friction resistance stress, in kN/m
(15)
4.2
Empirical formulas in relation with SPT from Japanese standards and codes In japan railway standards the use of SPT data is taken into priority than the cohesion intercept and angle of internal friction. For granular soil the angle of internal friction has been calculated by using the empirical formulas as suggested by Gibbs and Holtz (1957), De Beer (1975), Bishop and Eldin (1953), Nash (1953), Kirkpatrick (1965) experimental results which is reconsidered and revised by Aoki (1975). The angle of internal friction calculated by this formula is small (conservative) because of the 2step reduction by the revised data. Relation of SPT with angle of internal friction:
2
U circumference of pile, in m l thickness of strata, in m f r depends on p t In Japanese Railway Design Standard, the higher p t (the ratio of tip end bearing resistance by total bearing resistance) is, the less the total bearing resistance is evaluated. The reason is that the reliability of the tip end bearing resistance depends on the quality of tip end, and in Japan, the tip end quality seems to be not good because of the execution uncertainty by almost engineers.
N 1.85 v 0 .7 100
And the design bearing load capacity of long term is evaluated less than that of short term because of the action load characteristics.
0 .6
26
v t hw z hw
4. Empirical formulas in relation with SPT Pile capacity calculation by Standard Penetration Test SPT is one of the earliest applications of this test that includes two main approaches, direct and indirect methods. Direct methods apply N values with some modification factors. Indirect SPT methods employ a friction angle and cohesion values estimated from empirical formulas based on different theories.
(16)
(17)
where: angle of internal friction, degrees
N SPT value v effective earth pressure 50 kN / m 2 t soil density over the groundwater, in kN/m3
4.1
Empirical formulas in relation with SPT from Indian standards and codes SPT has been used in correlations for angle of internal friction, unit weight, shear strength etc. The real value of these properties requires a special care and laboratory technique. So, prediction of soil properties with the help of field tests such as SPT provides a good opportunity to obtain these parameter without using of more laboratory tests. Standard penetration tests SPT, rough measure the strength of soil. Following are the empirical formulas in relation of SPT. Relation of SPT values with angle of internal friction, Varghese (2005)
h w the depth of water table, in m soil density under the groundwater, in kN/m3 z the depth under the ground surface, in m
Relation of SPT with cohesion intercept The formula for calculation of cohesion intercept by using SPT value is not depicted in Japanese code of practice (Design Standards for Railway Structures and Commentary[Foundation]). But use of equation below for the calculation of cohesion intercept is widely accepted by most of engineers in Japan. The equation is based on the statistical analysis result followed by experimental investigated data in Japan. 3
Railway Structure Pile Design Comparison Considered with the difference of Japan and India
c
1 N 16
SPT value has been taken as per below statistical analysis:
(18)
Table3 Statistical analysis for selection of SPT
where: c Cohesion intercept, in kg/cm2 N SPT value
Average
Count
Min
Max
Geomean
28.25
4
10
40
24.83
5. Assumed Ground Condition Below are the assumed ground conditions to check the differences in the pile capacities calculated from Japanese standards and Indian standards.
Table4 Statistical analysis for selection of SPT
Table1 Physical properties of soil
Standard Deviation
95% Confidence
Selected Value
13.87
14.66
14
Depth, m
SPT N*
Soil Type
kN/m3
0 to 5
10
Silty Clay
16.0
5 to 15
25
Silty Clay
17.0
SPT value of 14 has been considered as average value along the pile shaft and 35 as average SPT value at pile tip. The capacity as calculated by the equation 3 & 4 turnout to be 2058.4 kN
15 to 20
38
Silty Sand
17.5
6.2
20 to 25
40
Silty Sand
18.0
Axial load carrying capacity of pile as per Japanese standards and codes:
*SPT values are average values of that stratum
Table5 Calculated strength parameters of soil (Japan)
Groundwater table is at surface and pile is circular in diameter with diameter of 1200 mm. Calculate the pile capacity at 20 m depth
Depth, m
SPT N*
Soil
0 to 5
10
Silty Clay
5 to 15
25
15 to 20 20 to 25
6.
Calculations
6.1
Axial load carrying capacity of pile as per Indian standards and codes: Axial pile load has been calculated by using two methods, first method is based on empirical formula interpretation of angle of internal friction and cohesion intercept and second method calculates the pile capacity by using direct formula of SPT value as given in IS2911part1section2 Method1 The results of interpretation of cohesion and angle of internal friction has been summarized in the Table2 below: Table2 Calculated strength parameters of soil #
kN/m3
60

16.0
Silty Clay
160

17.0
38
Silty Sand

34
17.5
40
Silty Sand

34
18.0
Depth, m
SPT N*
Soil
0 to 5
10
Silty Clay
5 to 15
25
15 to 20 20 to 25
c# kN/m2
#
kN/m3
63

16.0
Silty Clay
156

17.0
38
Silty Sand

40
17.5
40
Silty Sand

41
18.0
c# kN/m2
*SPT values are average values of that stratum By using formulas for cohesive soils based on SPT values, the cohesion intercept as calculated is found out to be almost same to that calculated by empirical formulas as used by Indian standards and codes. But by the using empirical formulas for calculation of angle of internal friction based on SPT values in granular soils, it is observed that the results are on higher side than that calculated by Indian standards and codes. In Japan, higher SPT values, results higher angle of internal friction and the same has been adopted without any limitations reason being SPT value results have more accuracy based on Japanese Standard and technique in Japan. The method of conducting SPT test in boreholes is almost same in Japan and in India, but the difference is in SPT sampler shoe inner diameter. The inner diameter of SPT sampler shoe in Japan is smaller (35mm) than that of India (38mm).
*SPT values are average values of that stratum
f r is 0.42 because p t is small ( pt 0.35) and the
# values are derived from empirical correlations and value of angle of internal friction is taken by limiting to 34 degrees
The
By using the formulas for cohesive soils and granular soils the axial capacity of pile turnout to be 3968.0 kN
3088 .5kN 0 .42 ( 4775 .0 2578 .6 )
Method2
The f r is determined by the Fig.1 as per Japanese Railway Standards (JRS)Design Standards for Railway Structures and Commentary [Foundation].
longterm design bearing load capacity as calculated by the Japanese Codes and standards is 3088.5kN
To calculate the axial capacity using SPT N value, the selection of SPT value is very important factor. Selected
4
(19)
fr : ground resistance coefficient
Railway Structure Pile Design Comparison Considered with the difference of Japan and India
code/standards used for evaluating the safe axial pile capacity, the capacities were compared for axial load calculations results. In general, the loads calculated using the Indian pile capacity calculation code Method1 are greater than the safe load bearing capacity calculated by using Indian pile capacity calculation code Method2. The Japanese method yields conservative pile capacity compared to the Method1 of Indian codes/standards. The capacity calculated by Method2 of Indian standards/codes is much more conservative compared to the Japanese codes/standards and also Method1 of Indian standards/codes.
1.4 1.2 1 0.8
Short term case
0.6 0.4
Long term case
0.2 0
0
0.1
0.2
0.3
0.4 0.5
0.6
0.7
0.8
0.9
1
Pt = Rtk/Rk
Fig1 Relationship between
f r and pt in case bored
The calculated bearing capacity by Japanese standards and codes is similar to an average of those calculated by Indian standards and codes (Mehod1 and Method2).
cast in situ pile (Japanese standards and codes) 7.
Comparison of the Bored Castinsitu Pile Design Results The calculated bearing capacity result comparison is shown below.
This calculation sample shows that there is not much difference between Japan and India standards and codes from the view point of bearing capacity as a result, although the formulas vary largely.
Japanese code estimates the tip resistance of bored cast in situ pile less than that estimated by Indian Codes. This is assumed to be the difference of philosophy of bored cast in situ pile performance.
References Aoki, N., de Alencar, D. 1975. An Approximate Method to Estimate the Bearing Capacity of Piles In: Proceedings, the 5th PanAmerican Conference of Soil Mechanics and Foundation Engineering, Buenos Aires, Vol.1, pp. 367376.
In Japan, the tip resistance of bored cast in situ pile is thought not to be large because of the debris and slimes when bored cast in situ pile is constructed. And in Japan, bearing stratum is not rocky, but diluvial soil in urban area where infrastructure is constructed.
Bishop and Eldin (1953). "The effect of stress history on the relation between f and porosity in sand" Proc. on 3rd ICSMFE, Vol.1, pp.100105.
Table6 Calculated bearing capacity comparison between Japan and India Code / Standard/ Method
Friction Tip Resistance Resistance (kN) (kN)
Codes, Indian Standard. "Code of practice for design and construction of pile foundations, (IS: 2911), Part I/Sec2." Bureau of Indian Standards, New Delhi (1980).
Safe Bearing capacity (kN)
Japan(Method1)
4775.0
2578.6
3088.5
India (Method1)
3883.0
6039.0
3968.0
Design Standards for Japanese Railway Structures and Commentary (Foundation), Maruzen (2012) E.De Beer (1975). "Influence of the mean normal stress on the shearing strength of sand" Proc. on 6th ICSMFE, Vol.1, pp.165169.
India (Method2) 2058.4 The friction resistance and tip resistance for given soils types i.e. silty clay and silty sand are calculated by static method for axial load. The soil parameters required are calculated by the correlations given in the previous section. The variation of friction resistance and tip resistance for given soil types varies largely in Indian Method1 and Japanese Method1. The comparison demonstrated that friction capacity as calculated by using Japanese method is about 23 % higher than as calculated by Indian Method1; on the contrary the tip resistance as calculated using Indian Method1 is about 134 % higher than as calculated by Japanese Method1. However, the safe bearing capacity as calculated by Indian Method1 is about 28.5% higher than Japanese Method1.
H.J.Gibbs and W.G.Holtz (1957). "Research on determining the density of sands by spoon penetration testing" Proc. on 4th ICSMFE, Vol.1, pp.3539. Kirkpatrick (1965). "Effect of grain size and grading on shearing behavior of granular materials" Proc. on 6th ICSMFE, Vol.1, pp.273277. Nash (1953). "The shearing resistance of a fine closely sand" Proc. on 3rd ICSMFE, Vol.1, pp.160164. Shigeyasu Y., (1969)."Soundings in the Alluvial Clay Stratums (On the results of several methods)" "Report of the Port and Harbour Research Institute Ministry of Transport, vol.8, No.1, pp.3758. Shooshpasha, I., et al. (2013). "Prediction of the axial bearing capacity of piles by SPTbased and numerical design methods." International Journal of GEOMATE 4(2): 560564.
8. Conclusion Two analyses have been conducted, based on the tip resistance and friction resistance for given study case of silty clay and silty sand. The silty clay encountered in boreholes from ground level to about 15 m followed by the thick layer of silty sand extended down till the end of borehole. Indian codes/standards and Japanese
Varghese, P. (2005). Foundation engineering, PHI Learning Pvt. Ltd.
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Railway Structure Pile Design Comparison Considered with the difference of Japan and India
Published on May 15, 2018
Railway Structure Pile Design Comparison Considered with the difference of Japan and India