10 –12, September 1. Geosynthetic-reinforced soil (GRS). Tatsuoka.pdf · Tokyo University of Science, Japan M. Tateyama Railway Technical Research Institute, Japan J. Koseki Institute

GRS structures recently developed and constructed for railways and roads in Japan

F. TatsuokaTokyo University of Science, Japan

M. TateyamaRailway Technical Research Institute, Japan

J. KosekiInstitute of Industrial Science, University of Tokyo, Japan

Second International Conference onTransportation GeotechnicsIS-Hokkaido 201210 – 12, September

Contents

1. Geosynthetic-reinforced soil (GRS) retaining walls with a staged-constructed full-height rigid facing

2. GRS integral bridge, comprising a girder integrated to the facings with the backfill reinforced with reinforcement connected to the facings

Contents



Near Shinjuku Station, Tokyo, constructed during 1995 – 2000

A GRS RW with a full-height rigid (FHR) facing supporting a very busy urban train line in Tokyo

Geosynthetic-reinforced soil retaining wall

Composite soil retaining structures: Three main elements: soil, reinforcement, and facing.

If material characterization, design, and construction are properly done, such walls will exhibit excellent performance while being economical.

Earth pressure

Facing Soil

Geogrid

Reinforcement What is the basic difference ?

(gravity) (cantilever) (T-shaped) (reinforced soil)

Conventional type RWs GRS RW

Conventional RC RW: a cantilever structure

Needs for a massive & strong facing & a pile foundation

Large forces in the facing & large overturning moment & large lateral load at the facing bottomEarth

pressure

Stress concentration

a

　　　　　　　　　

Embankment

Tie rod

RC anchorage

RC wall structure

Bore piles

Existing slope

Relativelygood subsoil

Existing slope

Rather stable supporting ground

Large diameter bored piles

Canti-lever RC RW

Backfill

RC anchorageTie rod

Conventional cantilever RW vs.GRS RW with a FHR facing for a highway in Yamagata, 1995

Previously constructed

　　　　　　　　　

Existing slope

　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　

GeotextileFull heightrigid facing

Excavation　　　　　　　　　　

Existing slope

Geogrid

Limited excavation

FHR facing

Newly constructed

GRS RW with FHR facing

11.3 m

Cantilever RC RW (constructed previously)

GRS RW under construction

Reinforced soil RWs

Tensile force inreinforcement atthe potential failure plane

Potential failure planeReinforcement

Active zone

Active earth pressurePA

Active zone

Reinforcement Potential active failure plane

Tensile force in reinforcement

Active earth pressure, PA

AFacing

Two basic force equilibriums with reinforced soil walls:(A) along the potential active failure plane

➔ always considered in design

Reinforced soil RWs



Active zone


Two basic force equilibriums with reinforced soil walls:(A) along the potential active failure plane

➔ always considered in design(B) at the facing ➔ very important, but often ignored

Active zone




A

B

Facing

Paramount importance of connection strength

Effects of connection strength on the tensile forces in the reinforcement & the stability of the active zone

Unstable active zone

Low connection strength

Low tensile forcein the reinforcement

Low confining pressure

→ Low earth pressure at the wall face

→ Low tensile forces in the reinforcement

→ In the active zone,low confining pressure, therefore, low stability

→ Low stability of the wall

Effects of connection strength on the tensile forces in the reinforcement & the stability of the active zone

Very stable active zone

Well connected

High connection strength

High tensile forcein the reinforcement

High confining pressure

→ High earth pressure at the wall face

→ High tensile forces in the reinforcement

→ In the active zone,high confining pressure, therefore, high stability

→ High stability of the wall

Rig

id fa

cingGRS RW with a FHR facing:

The facing is “a continuous beam supported at many levels with a small span”

Very small forces in the facing⇒ a simple facing

structure

Small overturning moment & lateral force at the bottom of the facing ⇒ usually, no need for a

pile foundation!

Earthpressure

Reinforcement

Increased stability against concentrated load on the wall crest

Tatsuoka et al. (1989) 12ISMFE, Rio de Janeio

　　　　　　　

Concentrated load

Failure plane when the facing is flexible or the connection strength is low

Failure plane forced to develop when using a FHR facing with high connection strength, resulting in a high wall stability

FHR facing

3D effects !

Against lateral load H, each unit of FHR facing together with reinforced backfill behaves as a monolith.

→A FHR facing becomes a foundation for super-structures, such as electric poles, noise barrier walls, bridge girders etc.

H

H



Active zone


Active zone




aFacing

Active zone




aFacing

1) The facing is only to prevent the spilling out of backfill.

2) The earth pressure at the facing should be made as possible as low.

3) The facing should be flexible enough to accommodate the deformation of supporting ground.

Previous explanations of the functions of facing

These explanations are wrong, or not accurate !

1) The facing is an important and essential structural component confining the backfill and developing large tensile force in the reinforcement.

2) The earth pressure at the facing should be high enough to provide sufficient confining pressure to the backfill.

3) The facing should be flexible enough to accommodate the deformation of supporting ground during construction, but should be rigid enough during service. This can be achieved by staged-construction.

The correct and accurate explanations

Damage to the connection due to relative settlement between the facing and the backfill.

Large load

No tensile strainsbefore removing the propping

Difficulty in compacting the backfill behind the facing

Need for a propping

FHR facing contributes to the wall stability, but several problems during wall construction if constructed before, or simultaneously with, the construction of the backfill.

□ Most of these problems can be solved by thestaged construction procedure …..

Uncontrolled movement upon the removal of the propping

5)5) Completion of wrapped-around wall

4)4) Second layer3)3) Backfilling & compaction

2)2) Placing geosynthetic &gravel gabions

Gravel gabionGeosynthetic

1) Leveling pad for facing

Drain hole

6)6) Casting-in-placeRC facing

Staged construction - 1:- Construction with a help of gravel gabions placed at the

shoulder of each soil layer








Drain hole


Lift = 30 cm

Good compaction of the backfill by:1) a small lift resulting from a

small vertical spacing of reinforcement layers; and

2) no rigid facing during backfill compaction






Drain hole









Drain hole


→ No damage to the connection between the facing and the reinforcement during and after construction.

→ Construction using compressive backfill on a compressive soil layer becomes possible.

Staged construction - 4:- After sufficient compression of backfill and supporting

ground has taken place, a full-height rigid facing is constructed by casting-in-place concrete directly on the wrapped-around wall.

10 cm


Typical polymer geogrid

RC facing are fixed to soil bags


鉄製のアンカー(直径13 mm）

30 cm 30 cm120 cm

30 c

m

60 c

mBackfill

Geogrid

FrameFresh concrete

Separator

Steel reinforcementWelding

Anchorplate

60 cm

Soilbag

Steel rod (13 mm in dia.）鉄製のアンカー(直径13 mm）

30 cm 30 cm120 cm

30 c

m

60 c

mBackfill

Geogrid

FormFresh concrete

Separator

Steel reinforcementWelding

Anchorplate

60 cm

Soilbag

Steel rod (13 mm in dia.）

A firm connection between the facing and the reinforcement by casting-in-place concrete directly on a geogrid-wrapping-around the wall face.



Adequate drainage by:1) drain holes in the FHR facing; 2) gravel bags immediately behind the facing: a

temporary facing before casting-in-place concrete and a vertical drain layer during service; and

3) if necessary, buried drain crossing the wall.

Staged construction - 5:- Completed.






Drain hole


Existing slope;large deformation is not allowed during reconstruction

In use1991

Re-construction of an existing slope to a vertical wall for a yard of high-speed trainat Biwajima, Nagoya

A yard of high-speed trains at Biwajima, Nagoya, 1989 - 1990 - Average wall height= 5 m & total length= 930 m Both sides of an existing railway

embankment were reconstructed to GRS RWs having a FHR facing under a severe space restriction

Average wall height= 5 mtotal wall length= 1,300 m

FHR facing

Geogrid(TR= 29.4 kN/m)

FHR facing

Geogrid(TR= 29.4 kN/m)

Amagasaki wall, directly supporting a very busy rapid railway, constructed 1991 - 1992

New construction of RWs for railways:- no conventional type RWs- no Terre Armée RWs - GRS RWs with a FHR facing in nearly all cases

History of elevated railway and highway structures in Japan

Conventional type RWs

Gentle slope

・Low stability・High deformability・Large space occupied Some cases

(basically no piles)

GRS-RW

・High cost-effectiveness

・Sufficiently high stability & stiffness

101

60

139

RRR-B : 910

162 20318

210

15

The total wall length= 136 kmat 910 sitesZero problematic case

Locations of GRS RWs with a stage-constructed FHR facing as of June 2012

101

60

139

RRR-B : 910

162 20318

210

15

Many for high-speed train lines

1995 20001990 2005

30

10

0

20

140

40

120

100

80

60

2010

Annu

al w

all l

engt

h （

km）

Tota

l （km

）

1995 Kobe Earthquake

Total

Annual

Restart of construction of new high-speed train lines(Shin-kan-sen)

2004 Niigata-ken-Chuetsu Earthquake

2011 Great East Japan EQ

From 1982: research at the University of Tokyo& Railway Technical Research Institute

Earthquakes

〈重力式擁壁〉

1995 Kobe EarthquakeFailure of gravity type wall at Ishiyagawa site

Original location

After 1995 Kobe Earthquake

5 m

+ ++

Original location


5 mOriginal location


5 m

+ ++

1995 Kobe EarthquakeFailure of leaning (gravity) type wall at Sumiyoshi site

++0.55 m

2.6 m

1.0 m

0.9 m1:

0.3

Unreinforced concrete

++0.55 m

2.6 m

1.0 m

0.9 m1:

0.3

Unreinforced concrete

+ +GRS RW with a staged-constructed FHR facing

1. Temporary wall of steel H-piles

2. Large diameter nail

3. FHR facing3. FHR

facing


Nailed wall

The numbers indicate the construction sequence.

+ +GRS RW with a staged-constructed FHR facing

1. Temporary wall of steel H-piles


3. FHR facing3. FHR

facing


Nailed wall

The numbers indicate the construction sequence.

Reconstruction

Why are GRS RWs much more stable than conventional type RWs?→ Evaluation by shaking table tests

Performance of RWs during the 1995 Kobe EQ.

Backfill & subsoil:dry Toyoura sand (Dr=88%)

Gravity type RW

Reinforced-soilRW with full-height rigid facing

20140

20

50ModelBackfill

Surchrge 1kPa

GRS RW with a FHR facing

(unit in cm)

Reinforcement (10 layers): grid of phosphor-bronze strips (t=0.2mm)

20

53ModelBackfill

20

Gravity type RW

Reinforcedzone

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40

20

40

60

80

100

Wal

l top

dis

plac

emen

t, d to

p(mm

)

Seismic coefficient, kh=amax/g

Gravity type

GRS RW (R1)

Subsoil 20 cm

Backfilldtop

5 cm 50 cm (R1) 53 cm (G)

Formation of the first shear bandin the backfill

Formation of shear bandsin the backfill

(Koseki et al., 2003)

Gravity type:less ductile failure

GRS RW (R1):more ductile failure

1 2 3 4 5 6 7 81.0

0.5

0.0

-0.5

-1.0

amax

Modified 1995 KoBe EQ.

Bas

e ac

cele

ratio

n (g

)

Time (sec)

Different resistance mechanisms

Seismic Force

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.80.8

1.0

1.2

1.4

1.6

1.8

補強材張力Ｔ(

水平震度（G）

Leaning

補強土擁壁0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

0

5

10

15

20

25

30

35

GRS RW

Tota

l nor

mal

forc

e,P

(kN

/m)

Seismic coefficient

Seismic coefficient

Seismic Force


Seismicforce

Bearing capacity, P

Seismic Force

Tensile force, T Increase

of tensile force

Less ductile

More Ductile

Bearing capacity failure

Surchrge 1kPa

20

140

53

b. Gravity type(G)

ModelBackfill53

a. Cantilever type(C)

(Dr=90%)

155Surchrge 1kPa

23cm20

ModelBackfill

20140

20

50

d. Reinforced-soil type 1(R1)

ModelBackfill

Surchrge 1kPa

53

140

1820

Surchrge 1kPa

c. Leaning type(L)

ModelBackfill

G: gravity

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40

20

40

60

80

100

Subsoil 20 cmC

L

Wal

l top

dis

plac

emen

t, d to

p(mm

)

Seismic coefficient, kh=amax/g

R2

R3Backfill

dtop GR1

GRS-RW with a FHR facing

5 cm 50 or 53 cm

C: cantilever L: leaning

8045

14020

20

50

e. Reinforced-soil type 2(R2)

ExtendedReinforcement

ModelBackfill

Surchrge 1kPa

14035

20

50

f. Reinforced-soil type 3(R3)

ModelBackfill

Surchrge 1kPa

R1

R2

R3

R: GRS-RW with a FHR facing

Backfill Backfill(Dr= 90 %)

Backfill


20

R2: very ductile & most cost-effective→current design practice

Tanata wall

Truncated longerreinforcement

Extended reinforcement

Silt rockSand rock

13.1

8 m

After remedy work

Railway (Jo-etsu line)

Shinano riiver

Gravel-filled steel wire

mesh basket

Rock bolt

GRS-RW with a FHR facing; slope: 1:0.3 (V:H); max. height= 13.2 m, vertical spacing of geogrid= 30 cm

Before failure: sand backfill including round-shaped gravel on sedimentary soft rock (weathered, more at shallow places)

After failureFailed

gravity RW

2004 Niigata-ken Chuetsu Earthquake

Silt rockSand rock

13.1

8 m

After remedy work

Railway (Jo-etsu line)

Shinano riiver

Gravel-filled steel wire

mesh basket

Rock bolt

GRS-RW with a FHR facing; slope: 1:0.3 (V:H); max. height= 13.2 m, vertical spacing of geogrid= 30 cm

Before failure: sand backfill including round-shaped gravel on sedimentary soft rock (weathered, more at shallow places)

After failureFailed

gravity RW

2004 Niigata-ken Chuetsu Earthquake

Another site

GRS RWs having FHR facing for railways, including high-speed trains, constructed before the 2011 Great East Japan Earthquake

Co

Aomori: 58Iwate: 23Akita: 1Yamagata: 3Fukushima: 1(total) 95

30 0 30 0 (A ll un it in m m )

1 00 5 75

1 00

60 0

5 ,40 0

Adjacent to Natori River, Sendai CityCompleted 1994Wall length= 400 m

No damage to all of the walls

47

←Nagamatchi Higashi Sendai→

● Masonry RW

● Unreinforced backfill (H= 5 m)● Gravelly sandy soil

Irrigation channel

Collapse of a wing RW for a bridge abutment (JR East)

(by the courtesy of the East Japan Railway Co.)

48

- Very fast reconstruction

- Emergent opening of service before the construction of a

FHR facing

Reconstruction of collapsed RW to GRS-RW


Completed wall

Failure of railway embankment at three locations by the Nagano-Niigata Border Earthquake (12 March 2011)


≒ 6.0

5,0

2.0

1.0

After failure

Mattress basketGravel

Stabilized soil

Welded steel fabric

Slope before failure

Railway track (Iiyama line) [All unit in m]

≒14.0

Reconstruction to GRS-RWs having a FHR facing

Floods, heavy rains and storm waves

101

60

139

RRR-B : 910

162 20318

210

15


Reconstruction of railway embankments that failed by flood, 1991

Geogrid (rupture strength TTR= 29.4 kN/m)

Gabions between the facing and the backfill and a large-diameter drainage pipe are not shown.

Railway track1V : 1.5H

1V : 1.5H

Geogrid (TTR= 58.8kN/m)

1V:0.2H

0.65 m

Secondary low-stiffness geogrid for compaction control

26.5

m

11 m

7 m

Geogrid (rupture strength TTR= 29.4 kN/m)

Gabions between the facing and the backfill and a large-diameter drainage pipe are not shown.

Railway track1V : 1.5H

1V : 1.5H

Geogrid (TTR= 58.8kN/m)

1V:0.2H

0.65 m

Secondary low-stiffness geogrid for compaction control

26.5

m

11 m

7 m

Several railway embankments in Kyushu failed by a heavy rainfall and a flood in 1989 and reconstructed GRS-RWs in 1991

101

60

139

RRR-B : 910

162 20318

210

15

In total 855 sites(no problematic case)


Reconstruction of embankment & RW that collapsed by heavy rain, Iiyama Line (JR East), July 2011

Failure of the fill constructed by cut & fill

EchigoTazawa

Tuzawa tunnel

Water fflow underthe normal condition

About 16 m

EchigoShikawatari

Failure by overflow of the water from the mountain

(Takisawa et al., 2012, JR East)

About 6 m

55

Key design factors in the reconstruction

– 14 days until the re-open of service required

– Minimized imported backfill (gravelly soil: C-40)

→ GRS RWConstruction of GRS RW

Completion of full-height GRS RW Staged-constructed FHR facing(Takisawa et al., 2012, JR East) (Takisawa et al., 2012, JR East)

Collapse of a masonry RW by scouring of supporting ground and associated erosion of the backfill

Tokamachi

About 3.8 mIruma River Bridge, A1

Doichi

57

(Takisawa et al., 2012, JR East)

Reconstruction of RW to GRS RW with a FHR facing

Geogrid (Ta= 30 kN/m)

FHR facing, staged-constructed after emergent train operation upon the completion of the GRS wall (w/o FHR facing)

Original masonry RW

Bed

Approach fill (cement-mixed gravelly soil, M-40; cement 50 kg/m3) to minimize the settlement of the approach fill

Completed GRS RW

Reconstructed truck(Takisawa et al., 2012, JR East)

10 days until the re-opening of service required: the original masonry RW needs a long construction period → GRS RW

Re-opening of service (with slowed-down running of trains)before constructing of FHR facing

Key design factors in the reconstruction

Staged construction of FHR facing

Collapse of conventional type RW by scouring

Flood

Scouring

GRS-RWs with a FHR facing has a high resistance against scouring

Better performance of GRS-RW with FHR facing

1. Scouring

3. Collapse of embankment

2. Over-turning of RW

River bed/sea shore

Flood

Failure of RW and backfill by scoring Failure of seawall for National Road No. 1, Kanagawa Pref., southwest of Tokyo, by Typhoon No. 9, 8 Sept. 2007

GRS-RW having a full-height rigid facing

10 March 2010

Pacific Ocean

Casting-in-place of concrete for FHR facing

Reconstruction to GRS RW with FHR facingSummary:

A number of GRS RWs having a staged constructed FHR facing performed very well during the 1996 Great Kobe and the 2011 Great East Japan Earthquakes.

A number of conventional type RWs and embankments that failed during recent severe earthquakes, heavy rains, floods and storms were reconstructed to GRS RWs of this type soon after the failure .

It was proven that this technology can construct stable RWs under very difficult design conditions requiring:1) a very short construction period;2) severe construction conditions (e.g., on a steep slope at a

water collecting place);3) high stability against severe seismic loads, heavy rains, floods,

storms; &4) low construction cost.

Contents



1. Piles

Technical problems with conventional type bridges

3. Backfill

Earth pressureDisplacement by earth pressure

Ground settlement & lateral flow due to the weight of backfill, and associated negative friction & bending of the piles.

2. RC abutment

Ground

5. Girder

4. Bearings (fixed or movable)→ High cost for construction &

long-term maintenance

Technical problems with conventional type bridge

Long-term settlement by self-weight, traffic load & seismic load

5. Girder

4. Bearings (fixed or movable)→ Low seismic stability

3. Backfill

Earth pressureDisplacement by seismic earth pressure

1. Piles

2. RC abutment

Ground

Ground settlement & lateral flow due to displacements by seismic load

What is a solution ?

Towards GRS Integral bridge:■ Problems with conventional

type bridges

■ Integral bridge; a structural engineering solution

■ GRS RW bridge; a geotechnical engineering solution

■ GRS Integral bridge;►the solution►Importance of strong connection between the reinforcement andthe facing

Conventional type

GRS Integral

GRS RW IntegralCombined

To solve several problems with backfill

To solve several problems with RC structures

Conventional typeConventional type

GRS IntegralGRS Integral

GRS RWGRS RW IntegralIntegralCombined



Integral bridge

2b. RC facing(abutment)

2a. Concrete framework and propping

1. Piles

2. RC facing

1. Piles

4. Backfill

3. Continuous girderIntegration

Integral bridge

Low construction & maintenance cost of the structural part, due to: a) no use of girder bearings & b) the use of a continuous girder

However, several unsolved old problems !

2. RC facing

1. Piles

4. Backfill

3. Continuous girderIntegration

Long-term service issue: a. settlement by self-weight & traffic load b. large deformation by seismic load

Displacement due to earth pressure

Ground settlement & lateral flow due to the weight of backfill, and associated negative friction & bending of the piles.

Earth pressure(static & dynamic)

Backfill

RC facing

Pile

Backfill

Seasonal thermal expansion & contraction of the girder

Settlement

Increase in the earth pressure

Lateral cyclic displacements

Continuous girder

A new problem with integral bridges !

Static lateral cyclic loading tests under plane strain conditions in 1g (considered model scale: 1/10)

Wall height:50.5 cm

L

50.5 cmH=50.5 cm

D

K

Unreinforced backfill:

A significant increase in the passive earth pressure with cyclic loading

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Late

ral d

ispl

acem

ent o

f fa

cing

, d/H

(%)

0 5000 10000 150000

1

2

3

4

Initial state (K0=0.5)

Tota

l ear

th p

ress

ure

coef

ficie

nt, K

Elasped time (second)

Constant amplitude, D/H

0 5000 10000 150002.0

1.5

1.0

0.5

0.0 L= 35 cm

L= 20 cm

L= 10 cm

Set

tlem

ent a

t the

cre

st

of b

ackf

ill, S

g/H (%

)

Elapsed time, t (sec)

Distance from the back of facing, L= 5 cm

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Late

ral d

ispl

acem

ent o

f fa

cing

, d/H

(%)

Why ?

L

50.5 cmH=50.5 cm

D

K

Unreinforced backfill:

Significant settlement in the backfill with cyclic loading

Constant amplitude, D/H

a)

Dual ratchet mechanismFormation of active wedge

S→A1

No major deformation outside the active wedge

b)

A1→P1

Active wedge deforms as part of passive wedge, not recovering the active displacement during S→A1

Formation of passive wedge

c)

Dual ratchet mechanism

P1→A2

No displacement & deformation of passive wedge outside the active wedge

Reactivation of active displacement of active wedge

d)

A 2→P2

Reactivation of passive deformation of passive wedge

Towards GRS Integral bridge:■ Problems with conventional

type bridges




Conventional type

GRS Integral









1 1: GRS RW2: FHR facing

After sufficient deformation of backfill and supporting ground, construction of full-height rigid (FHR) facing ►►► Staged construction

GRS-RW bridge5. Girder

1 1: GRS RW

3

4. Movable and fixed bearings

3: Sill beam

2: FHR facing

A high cost/performance ⇒ about 20 abutments constructed.

GRS-RW bridge

However, new problems by a relatively low seismic stability of sill beams and relatively low stiffness of the backfill.

→Modification: placing the girder on the top of the facing via bearings

4. Girder

1 1. GRS RW2. FHR facing

3. Movable & fixed bearings Takada

Nishi Kagoshima

Hakata

New bullet train line

Existing bullet train line

Nagasaki

Bullet train line under planning

A New High-Speed Train Line in Kyushu Island

The first bridge abutment at Takada, completed March 2003.

Staged construction procedure for the new type bridge abutment (1)

Cement-mixed gravel

Soil Backfill

1

Cement-mixed gravel

Soil Backfill

2

3

To avoid the damage to the connection between the reinforcement and the facing due to relative settlement

Staged construction procedure for the new type bridge abutment (2)

Cement-mixed gravel

Soil Backfill

1

Cement-mixed gravel

Soil Backfill

2

3

To avoid the damage to the connection between the reinforcement and the facing due to relative settlement

A 15 m-high GRS-RW bridge abutment at Mantarofor a new high-speed train line, the south end of Hokkaido

The total number of GRS RW bridge abutments completed or designed (as of June 2012): 59

Oct. 2011 Aug. 2012

Fixed bearing

■Despite a high cost-effectiveness, still serious problems by using bearings (i.e., high cost for construction & low seismic stability)

Why not removing the bearings ?

Towards GRS Integral bridge:■ Problems with conventional type

bridges




Conventional type

GRS Integral









Firmly connected

2. FHR facing

3. GirderStructurally integrated

0. Ground improvement (when necessary)

1. GRS wall

Gravel bags

GRS Integral BridgeTwo-span bridge (longer than 30 m)

Displacement-controlled loading system

Lateral displacement

Load cell

Hinge support

129.5

8.5

　5 10 20 35

50

.5

Settlement of the crest

Box width: 40

Air-dried Toyoura sand (Dr = about 90%)

9 separated load cells: LCs

[unit : cm]

8 polyester reinforcement layers

Distance (cm) from the back of the facing



Load cell

Hinge support

129.5

8.5

　5 10 20 35

50

.5


Box width: 40



[unit : cm]



Load cell

Hinge support

129.5

8.5

　5 10 20 35

50

.5


Box width: 40



[unit : cm]

8 polyester reinforcement layers

Distance (cm) from the back of the facing

Hinge-support: or no support with a depth of 3 cm

11.5 cm

Reducing the effects of thermal deformation of the girder by:1) reinforcing the backfill; and 2) connection between reinforcement and facing

0 50 100 150 2003.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

S5

5 cm

S5

5 cmNR (no reinforcement): D/H= 0.2 %

NR: D/H= 0.6 %

Res

idua

l se

ttle

men

t of th

e ba

ckfil

l at

5 c

m

back

of

the f

acin

g, S

g/H (%

)

Number of loading cycles, N (cycles)

H

D/H= 0.2 or 0.6 %

Hinge-support

NR: not reinforced

0 50 100 150 2003.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

S5

5 cm

S5

5 cm

Reinforced & No Connected (R & NoC): D/H= 0.2 %

NR (no reinforcement): D/H= 0.2 %

NR: D/H= 0.6 % R & NoC:

D/H= 0.6 %

Res

idua

l set

tlem

ent o

f the

bac

kfill

at 5

cm

bac

k of

the

faci

ng, S

g/H (%

)


NR: not reinforced R&NoC: reinforced, but no connection ➔ This is not a

solution !

H

D/H= 0.2 or 0.6 %

Hinge-support

R&C: reinforced; and connection

0 50 100 150 2003.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

S5

5 cm

S5

5 cm

Reinforced & No Connected (R & NoC): D/H= 0.2 %

NR (no reinforcement): D/H= 0.2 %

Reinforced & Connected (R & C):D/H= 0.2 %

NR: D/H= 0.6 % R & NoC:

D/H= 0.6 %

R & C: D/H= 0.6 %

Res

idua

l set

tlem

ent o

f the

bac

kfill

at 5

cm

bac

k of

the

faci

ng, S

g/H (%

)


NR: not reinforced R&NoC: reinforced, but no connection

D: displacement transducerM: movable (sliding) shoe F: fixed (hinged) shoe L: L shaped metal fixture

64.4

Width= 60 cm60.8

[Unit: cm]

Nine local load cells.

Five local load cells

D

D

51

205.8

35

5 4.53.4

5 15 35

456

20

FM

Mass of 205 kg (equivalent length of model girder= 2.0m)

Conventional type bridge ‘CB)

51

205.8

35

54.5 68.1

5 15 3560.8

D

Nine local load cells

D


456

20

Integral bridge (IB)

L L

205.8

5135

5 5 15

D

4011

60.8 68.135

D

GRS RW bridgeConnected

FM

Target for photogrametric method

Grid reinforcement

51

205.8

35

54.5 68.1

5 15 3560.8


456

20

L L

GRS Integral bridge

D

D

Connected

Grid reinforcement

Shaking table tests in 1g

(considered model scale: 1/10)

dT

dB

GRS Integral

Most stable

Conventional

GRS RW

Integral

Lateral displacements

0

20

40

60 Dislodging of girder

Integral

GRS RW (displacement at the sill beam)

Late

ral d

ispl

acem

ent a

t top

, d T (

mm

)

GRSIntegral

Conventional(gravity)

0 200 400 600 800 1000 1200

0

20

40

60

GRS RW


Integral

GRSIntegral

Base acceleration, max (gal)

Late

ral d

ispl

acem

ent a

t bot

tom

, d B

(mm

)

Residual settlement at the backfill

S5

5 cm

0 200 400 600 800 1000 1200

60

40

20

0GRSIntegral

Integral


GRS RW

Base acceleration, max (gal)S

ettle

men

t of t

he b

ackf

ill, S

5 (mm

)

Out of measument range

GRS Integral

Most stable

Conventional

GRS RW

Integral A very high dynamic stability of GRS Integral bridge Why?

The first mode of dynamic deformation, modeled by a damped single-degree-of-freedom system

Sinusoidal input acceleration(amplitude: αb, input frequency: fi)

MeasuredAccelerationmagnification ratio:

M = αt/αbPhase difference: φ

Response acceleration (amplitude: αt)

Back-cacluatedNatural frequency; f0→Tuning ratio: β = fi/f0Damping ratio: ξ

Response of GRS Integral BridgeIncrease in the number of loading cycle & base acceleration → Structural softening

Decrease in the natural frequency f0→ increase in β

Increase in the response ratio M and the phase difference φ

Approaching the resonant state → failure

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.5 1.0 1.5

Res

pons

e ra

tio o

f acc

eler

atio

n, M

I

IIIVI VIII

VII IXX XI (1)

XI (7)

1.0

0.80.60.5

0.4

0.3

= 0.2

Damping ratio:

XII

Tuning ratio, = fi/f0

-2.0

-1.5

-1.0

-0.5

0.0

0.5

0.0 0.5 1.0 1.5

Phas

e di

ffere

nce,

(r

ad)

I III VI

VII

XIX

XI (20)

VIII

XI (1)

XII

0.5

0.6

0.8= 1.0

Damping ratio:

0.4

0.30.2

Tuning ratio, = fi/f0

Solid curves: theoretical

Resonant state

Tuning ration, β＝ fi/fo

Res

pons

e ra

tio o

f ac

cele

ratio

n, M

Phas

e di

ffere

nce,

φ(in

radi

an)

Loading stage(No. of cycle at each stage)

Tuning ratio,

Four reasons for a very high seismic stability of GRS IBamong the different bridge types

1) The the largest initial value of f 0 (i.e., smallest initialvalue of β ) → the smallest initial response

2) The smallest decreasing rate of f0 (i.e., the smallestincreasing rate of β )

→ the smallest possibility to reach the resonance

3) The largest damping ratio at failure→ the smallest response

4) The largest response acceleration at failure(i.e., the largest strength)

III

III IV V VI

VII

VIIIIX

XXI

XII0 200 400 600 800 1000 1200 1400

0

5

10

15

20

25

30

35

40

Nat

ural

freq

uenc

y of

brid

ge,

f 0 (H

z)

GRS-RW GRS-IB

CB

: Resonance state (fi= 5Hz)

Base acceleration amplitude, Amp[üb] (gal)

Very slow to reach the resonance

A high initial f0

Very fast to reach the resonance

A low initial f0

Four reasons for a very high seismic stability of GRS IBamong the different bridge types

1) The the largest initial value of f 0 (i.e., smallest initialvalue of β ) → the smallest initial response

2) The smallest decreasing rate of f0 (i.e., the smallestincreasing rate of β )

→ the smallest possibility to reach the resonance

3) The largest damping ratio at failure→ the smallest response

4) The largest response acceleration at failure(i.e., the largest strength)

0 500 1000 1500 20000.0

0.2

0.4

0.6

0.8

1.0 ..

..

GRS-IB-T

GRS-IB-C

GRS-IBIB

GRS-RW

Dam

ping

ratio

a

t fai

lure

Acceleration at resonance (gal)

CB

Response acceleration at resonance, Amp[ut]resonance

(strength)

Base acceleration at resonance, Amp[ub]resonance

A single value of damping ratiois presented for the respective models.

Response acceleration at resonance, (αt)resonance(dynamic strength)

Input acceleration at resonance, (αｂ)resonance

GRS-IB-C-T

Accelerations and damping ratios at the start of failure (i.e., at resonance) (fi= 5 Hz)

Very high strengths & very high damping ratios

Acceleration response spectra of NS component of the earthquake motion recorded at JMA Kobe, 1995 Kobe Earthquake (by the courtesy of Dr Izawa, J., RTRI Japan).

0.1 0.5 1 50

1000

2000

3000

周期 (sec)

応答

加速

度 (g

al)

1995兵庫県南部地震神戸海洋気象台 NS成分

h=5% h=10% h=20% h=30% h=40% h=50% h=60% h=70%

Period T0 = 1/(frequency f0) (second)R

espo

nse

acce

lera

tion

(gal

) Damping ratio ξ (%)= 5

10

2030

40, 50, 60 & 70

Implications of the test results in the seismic design

Earth pressure cells Earth pressure cells

Cement-mixed backfill Well-graded gravelly soil

5.55

m

14.75 m

April. 2009

A full-scale model of GRS integral bridge, completed Feb. 2009 at Railway Technical Research Institute, Japan

27 November 2008

The initial natural period of the full-scale model:T0= 0.046 sec (Yokoyama et al., 2012); much smaller than Tp of ordinary strong seismic motions (Tp= 0.35 sec in this case)

0.1 0.5 1 50

1000

2000

3000

周期 (sec)

応答

加速

度 (g

al)


h=5% h=10% h=20% h=30% h=40% h=50% h=60% h=70%

Period T0 = 1/(frequency f0) (second)

Res

pons

e ac

cele

ratio

n (g

al) Damping ratio ξ (%)= 5

10

2030

40, 50, 60 & 70

Implications of the test results in the seismic design

0.1 0.5 1 50

1000

2000

3000

周期 (sec)

応答

加速

度 (g

al)


h=5% h=10% h=20% h=30% h=40% h=50% h=60% h=70%

Period T0 = 1/(frequency f0) (second)

Res

pons

e ac

cele

ratio

n (g

al) Damping ratio ξ (%)= 5

10

2030

40, 50, 60 & 70

4) A higher strength of GRS IB than CB

Response acceleration at failureCB: Conventional type Bridge

GRS IB: GRS Integral Bridge

CB

GRS IB

1) Lower initial response acceleration of GRS IB than CB2) A smaller increase in the natural period To of GRS IB than CB3) A higher damping ratio of GRS IB than CB

The four reasons, all due to the integration of the girder, abutments and approach fills.

The first GRS integral bridge, at Kikonai for a new high-speed train, constructed 2011

Sapporo

Shin-Hakodate

Shin-Aomori

Seikan Tunnel(about 5 km-long)

First full-scale GRS integral bridge, for a new high-speed train line, Kikonai at the south end of Hokkaido

(14th Oct. 2011).

GCM: Ground improvement by cement-mixing

5.04 2.21.0

5.42.21.0

0.7 0.7

[All units in m]

GCM

Road surface

12.0

GCMGL= 5.0

Original ground

Backfill (uncemented)Backfill (cement-mixed gravelly soil)

6.1

10.75

EastWest RC slab

0.6

0.6

First full-scale GRS integral bridge, for a new high-speed train line, Kikonai at the south end of Hokkaido

(31 July 2012).

Not long, but the beginning of a long history (I hope)


5.04 2.21.0

5.42.21.0

0.7 0.7

[All units in m]

GCM

Road surface

12.0

GCMGL= 5.0

Original ground


6.1

10.75

EastWest RC slab

0.6

0.6

Great tsunami2011 Great East Japan Earthquake

Unreinforced backfill

Concrete panel facing

Drainage ditch

Concrete slab on the crest

Leveling pad

Sheet pile

FoundationFoot protection work

Tetrapod

Recurved parapet

Concrete panel facing

Total collapse of coastal dykes by overflow of tsumani

Flowing down of tsunami current along the down-stream slope:(1) Scouring in the ground; and strong uplift forces (2) Loss of the stability of concrete slab (not fixed) of the down stream

slope.(3) Erosion and wash away of the backfill (4) Loss of full-section

Stage (4) Stage (4)

Total collapse of coastal dykes by overflow of tsumani

Flowing down of tsunami current along the down-stream slope:(1) Scouring in the ground; and strong uplift forces (2) Loss of the stability of concrete slab (not fixed) of the down stream

slope.(3) Erosion and wash away of the backfill (4) Loss of full-section

Model tests at Tokyo University of Science

Conventional type- unreinforced backfill- discrete concrete panels on slopes and top

Smallest cross-section

Model tests at Tokyo University of Science

GRS coastal dyke- reinforced backfill- continuous panels connected to the reinforcement

Various types of GRS coastal dike proposed as a barrier for over-flowing tsunami

Planar reinforcement (e.g., geogrid)

Concrete facing (connected to reinforcement

Foot protection to prevent scouring

Flow-away of bridge girder by great tsunami2011 Great East Japan EarthquakeA railway bridge (Tsuyano-gawa bridge) that lost multiple simple-supported girders by tsunami forces

KOSA, Kenji (2011)：Bulletin of JAEE, No.15, Oct.

Over 340 bridges collapsed by tsunami,mostly by flow-away of girder and/or backfill

Both bearings & backfill are weak components for seismic & tsunami forces

Integrated girder and facingsGeosynthetic-reinforced backfillA solution by GRS integral bridge

Railway that can survive a great tsunamiGRS integral

bridgeGRS RW with FHR

facing

GRS coastal dyke

Evacuation shelters along elevated railway

Railway Technical Research Institute

Backfill

Geogrid

Gravel bags

Haipe at SanrikuRailway (August 2011)

宮古市

久慈市

North

Sanriku Railway (under restoration)

津波到達域

Journal of JSCE (May 2012)

MiyakoCity

KujiCity

Areas inundated by tsunami

Haipe at Sanriku Railway (August 2011)

Seaside

GRS integral bridge at Haipe for SanrikuRailway (the construction will soon start)

Geogrid connected to the abutment

Abutment A1

A232.0 m

17.99 m

Pier P1Abutments and pier that survived the earthquake

Fill

Geogrid

Concrete facing connected to geogrid

Central cross-section

28.00 m

P2 Approach fillA1 P1

Embankment

Embankment

Approach fill

Approach fill

4.7 m 5.4 m

Koikorobe at Sanriku Railway (August 2011)

Seaside Seaside

GRS integral bridge at Koikorobe for Sanriku Railway (the construction will soon start)

Approach fill

Geogrid connected to the abutment

Abutment A1

A1 P1 A219.93 m 19.93 m

Pier P1

Abutments and pier that survived the earthquake

Fill

Geogrid

Concrete facing connected to geogrid

Central cross-sectionEmbankment

Embankment

Approach fill

Approach fill

4.7 m

6.22 m

Summary

The GRS integral bridge:1) no use of girder-bearings; 2) use of a continuous girder integrated to the facings; 3) reinforcing the backfill with reinforcement connected

to the facing; and 4) after the completion of reinforced backfill,

construction of a full-height rigid facing then the girder.

The backfill may be cement-mixed appropriately to increase the seismic stability and to decrease the residual deformation.


5.04 2.21.0

5.42.21.0

0.7 0.7

[All units in m]

GCM

Road surface

12.0

GCMGL= 5.0

Original ground


6.1

10.75

EastWest RC slab

0.6

0.6

Typical polymer geogrid10 cm

Conclusions1. Geosynthetic-reinforced soil retaining walls (GRS RWs)

having a stage-constructed full-height rigid (FHR) facing have been constructed as important permanent RWs for a total length of more than 135 km in Japan. It is now the standard RW technology for railways.

Many others were also constructed for highways and others.

Its current popular use is due to not only high cost-effectiveness, but also high performance, in particular during severe earthquakes

(to be continued)

Conclusions (continued)

2. Many embankments and traditional type RWs that failed during recent severe earthquakes, heavy rains, floods and storms in Japan were reconstructed to GRS RWs with a stage-constructed FHR facing. It was proven that this technology is highly cost-effective.

(to be continued)

Conclusions (continued)

3. A new bridge type, called the GRS integral bridge, is proposed, which comprises an integral bridge and geosynthetic-reinforced backfill.

GRS integral bridges would exhibit essentially zero settlement in the backfill and no structural damage to the facing by lateral cyclic displacements of the facing caused by seasonal thermal expansion and contraction of the girder, while their stability against seismic loads and tsunami is very high.


5.04 2.21.0

5.42.21.0

0.7 0.7

[All units in m]

GCM

Road surface

12.0

GCMGL= 5.0

Original ground


6.1

10.75

EastWest RC slab

0.6

0.6

Thank you for your kind attentions !

Documents

10 –12, September 1. Geosynthetic-reinforced soil (GRS). Tatsuoka.pdf · Tokyo University of Science, Japan M. Tateyama Railway Technical Research Institute, Japan J. Koseki Institute