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2014/6/10
1
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi MinhTHE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
INTRODUCTION OF BASE ENLARGEDPRE-BORING METHOD WITH NODULAR PILE
~HYPER-MEGA METHOD~
Yusuke Homma
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Introduction of Hyper-MEGA methodDiameter : φ440-300 ~ φ1200-1000
(nodule diameter – shaft diameter)Length : The maximum length is up to 68.5m.
There are many cases of more than 60m length.
Material:Nodular pile : PHC & PRCSpun pile : PHC, PRC, SC, Steel
Concrete strength : 85, 105, 123N/mm2 & more
ω : enlarged ratio (1≦ω≦2)
ω= De /( Do +0.05)
De:enlarged excavation diameterDo:nodule diameter
Enlarged ratio ω
Conventional = 1.15↓
Hyper-Mega = 1.0~2.0
more than 2 times bearing capacity
Nor
mal
Exc
avat
ion
Part
Enla
rged
Exc
avat
ion
Part
2m o
r 50%
of P
ile L
engt
h
Enla
rged
Gro
uted
Bas
e Pa
rt 2m
Enla
rged
Shaf
t Par
t
Low strengthcement
High strengthcement 1,
000m
m
Enlarged Excavation Diameter De
2014/6/10
2
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Procedure of Hyper-MEGA method
①excavation ②expanded blade~enlarged excavation
Expanded blade and enlarged excavation
③mixing repeatedly
Mixing and S
tirred while
injecting cement slurry
④ forming the grouted base ~pull out
Forming the grouted base
then Pull -up
⑤setting pile
Setting pile
Excavation
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Overview of the Hyper-MEGA method Welding Pitching Pile Setting Pile
Enlarged auger-head
Screw
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Alloable vertical bearing capacity of soil
Equation of vertical bearing capacity
Soil of pile-toe Hyper-Mega methodJapanese general pre-boring method
TCXD-205 in Vietnam
sandy and gravelly
α=240ω1.5+90ω(330~858)
250 300 or 400
clayeyα=210ω1.25+90ω
(300~679)250 300 or 400
( ) ψγβα cussp LqLNANRu ++=
End bearing capacity factor:α
Ru
αN Ap
End bearing capacity: Ultimate bearing capacity
: End bearing capacity factor: Average N value for pile toe: Cross section of end nodular diameter
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Procedure of Hyper-MEGA method
Equation of vertical bearing capacity
( ) ψγβα cussp LqLNANRu ++=
SoilHyper-mega method Japanese
general pre-boring method
TCXD-205in VietnamStraight part
Nodular pile of enlarged part
β Ns(sand and gravelly)
5.0 Ns (30+5.5Ns)ω 3.3 Ns 2.0Ns
γ qu (clayey) 0.7 qu (20+0.5qu)ω 0.5 qu 0.5qu
Shaft bearing resistance factor : β, γ
Β,γ NsLsquLc
: Shaft bearing resistance factor: Average of N value of sandy soil: total length of pile in contact with sandy soil: Mean value of axial compressive strength : total length of pile in contact with clayey soil
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Result of loading test
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 2000 4000 6000 8000 10000 12000
Dept
h G
.L-
(m)
Load (kN)
20 40N Value
60
10
5
15
0 0
G.L
- (m
)
20
25
30
35
0
5000
10000
0 50 100 150
Pile
hea
d lo
adPo
(kN
)
Pile head displacementSo, Pile toe displacementSp (mm)
Pile head displacement
Pile toe displacement
These database is used to get license of"ASSESSMENT OF TECHNOLOGY FOR BUILDING CONSTRUCTION GBRC FOUNDATION" (GBRC 05-23A-001~003)and "INFRASTRUCTURE AND TRANSPORATION MINISTRY" (TACP-0210~0214).
Static loading tests were carried out in 53 locations.
・pile:φ500-400 + φ500・pile length:30m・ω=2.0
Load-displacement curve Axial force distribution
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Study of end bearing capacity<CONVENTINAL method>
Pp=α・N・Ap
α=250 (1)
<Hyper-Mega method>
*Constituted by the combination of resistance Ppp of the pile bottom face and the friction Ppf of the grouted base.
*considered to change of the base grouted diameter
Pp=Ppp+Ppf
α=αp+αf=aωb+cω (2)
Pp
Gro
uted
Bas
e
Shaf
t fr
ictio
n of
gro
uted
bas
e P p
f
load bearing capacity of the bottom face of the grouted base
Ap
position 2m above the pile toe
lowermost nodebottom face
pile toe about 0.35m
Ppp
Ppf 2.0m
Pp=Ppp+Ppf
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
End Bearing Capacity Factor ( α )
Sandy & Gravelly:α=240ω1.5+90ω
0
200
400
600
800
1000
1 1.2 1.4 1.6 1.8 2
αp=
qpp
/ N (
kN/m
2)
enlargement ration ω
sandy soilgravelly soilregression curve:315.7 1.455 calculation:240 1.5
0
2000
4000
6000
8000
10000
0 20 40 60 80
(qp
-24
0 ω
1.5
N) /
ω(k
N/m
2)
N
sandy soilgravelly soilregression curve 219.2 lower limit 98.2 calculation 90
ω=1.0 → α= 330, ω=2.0 → α= 858
αp=240ω1.5
Pp
Gro
uted
Bas
e
Shaf
t fr
ictio
n of
gro
uted
bas
e P p
f
Ap
Ppf 2.0m
load bearing capacity of the bottom face of the grouted base
Ppp
Pp=Ppp+Ppf
αf=90ω
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
End Bearing Capacity Factor ( α )
Clayey soil:α=210ω1.25+90ω
ω=1 → α= 300, ω=2→ α= 679
Pp
Gro
uted
Bas
e
Shaf
t fr
ictio
n of
gro
uted
bas
e P p
f
Ap
Ppf 2.0m
load bearing capacity of the bottom face of the grouted base
Ppp
Pp=Ppp+Ppf
0
500
1000
1500
2000
2500
1.0 1.2 1.4 1.6 1.8 2.0
α p=
qpp
/N(k
N/m
2 )
enlargement ration ω
clayey soil
excluded data to statistics
regression curve:280.5 1.259
calculation:210 1.25
0
2000
4000
6000
8000
10000
0 20 40 60 80
(qp -
210ω
1.25
N)/ω
(kN
/m2 )
N
calyey soillower limit 99.8 calculation 90
αp=210ω1.25
αf=90ω
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Shaft Resistance Factor (β & γ) for Nodular pile
0
200
400
600
800
0 20 40 60 80
fs/ω
(kN
/m2)
Ns
sandy soilregression curvemean-1.06σcalculationJapanese generalVietnamese standard
Fs = (30+5.5Ns)ω×DoπLs
0
50
100
150
200
250
0 100 200 300 400
fc/ω
(kN
/m2 )
qu (kN/m2)
clayey soilregression curvemean - 1.06σcalculationJapanese general & Vietnamease standard
Hyper-Mega method
more than 2 times
more than 20%
Spun Pile Nodular Pile
Ground
In some cases of spun-pile, friction capacity is determined by between shaft cement slurry and pile.→ Spun-pile is proportional to pile-diameter. In case of nodular-pile against that, that is always determined by between shaft cement slurry and soil, because it can get high adhesion force by nodular.→Nodular-pile is proportional to excavation-diameter.
Hyper-Mega method
Sandy soil
Clayey soil
Fc = (20+0.5qu)ω×DoπLc
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Comparison of Calculation and Static load test result
Static load test result > Calculation 1.24 times
0
10000
20000
30000
40000
50000
0 10000 20000 30000 40000 50000
Bea
ring
capa
city
by
load
test
Rt (
kN)
Bearing capacity from applied equation Rc (kN)
Toe:Sand
Toe:Gravel
Toe:Clay
Rc=Rt
Ration of average
These database is used to get license of "ASSESSMENT OF TECHNOLOGY FOR BUILDING CONSTRUCTION GBRC FOUNDATION" (GBRC 05-23A-001~003) and "INFRASTRUCTURE AND TRANSPORATION MINISTRY" (TACP-0210~0214).
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Design Procedure on Vietnam
Pile diameter
(mm)
Pile Length(m)
Designedcapacity
(kN)
Minimumplaned
load(kN)
Ultimate capacityby load test
(kN)
1200 60 9,000 18,000 14,400 20% ↓
1000 60 7,000 14,000 9,800 38% ↓
Designed by Cast-in Place Pile
In Vietnam, it is necessary to confirm the designedbearing capacity in advance in construction site.
Loading test must be carried out using designed piles.
If designed capacity can be obtained by loading test,We have to redesign the pile foundation of building.
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
We can surely determine the specification of pile which is satisfied with designed capacity, from advanced loading test.
Design Proposal using Hyper-MEGA Method in Vietnam
The greatest feature of Hyper-MEGA Method is that this method can be changed the vertical bearing capacity by control of the enlargement excavation rate in the range of 1 to 2 times, under the same specification pile.
ω=1.0 ω=1.2 ω≧1.2The capacity of pile is designed as ω=1.0 .
In investigating the bearing capacity of designed pile, the piles with specification of more than ω=1.0 are constructed in addition to ω=1.0
Even if the bearing capacity of ω=1.0 is less than designed capacity, another pile can fulfill it.
enla
rged
exc
avat
ion
part
enla
rged
exc
avat
ion
part
enla
rged
exc
avat
ion
part
2014/6/10
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THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh
Design Proposal using Hyper-MEGA Method in Vietnam
In recent year, a new pre-cast pile installation method forhigh load-bearing capacity is being actively developed inJapan. This Hyper-Mega method can set the enlargementfactor to a pile diameter of 1 to 2 times without keeping afixed value, and can get bigger friction resistance by nodularpile. Here is the evaluation of vertical bearing capacitythrough the loading test results.-------------------------------------------------------------------Because now pre-boring method like the Hyper-Mega
method is not general in Vietnam, we want to introduce theHyper-Mega method to Vietnam.
Thank you very much !
THE 1st WORKSHOP ON NEW PILE FOUNDATION TECHNOLOGIES IN VIETNAM 20/6/2014, Ho Chi Minh