Reinforced soil walls-6 · (()kN/m) 1 12.5 kPa Frictional with lap length of 1.3m 20.6 (pullout/partial rupture) 2 24.5 kPa Frictional with lap length of 1.3m 31 (pullout/partial

Geosynthetics and Reinforced Soil Structures

Testing Requirements Testing Requirements for Design of Reinforced

Soil WallsSoil Walls

Prof K. RajagopalDepartment of Civil Engineeringp g g

IIT Madras, Chennaie mail: gopalkr@iitm ac ine-mail: [email protected]

Tests Required for the Design of R i f d S il R t i i W llReinforced Soil Retaining Walls

• Properties of soil• Properties of soil• Properties of reinforcement• Soil-reinforcement interaction factors• Reinforcement facing connection• Reinforcement-facing connection

Reinforced Soil Walls - 6 2/59

SHEAR STRENGTH SHEAR STRENGTH PROPERTIES OF SOIL

• C=0 (cohesive strength is neglected)• Friction angle determined from small or large-box

shear tests (stress state in direct shear box similar to that behind retaining wall)R f l i th t t h ld• Range of normal pressures in the tests should correspond to those expected in reinforced soil fill

• Peak friction angle is used for designsPeak friction angle is used for designs


Longterm Allowable Design Strength

CRF TT ultLTDS

Tult from index tension tests (ASTM D6637 or ASTM D4595)

FSFBFDFCT LTDS

ult ( )

FC is the environmental degradation factor

FB is the biological degradation factor

FD is the construction induced damage (depends on method of compaction, size of aggregate etc.)

FS i ll f t f f tFS is overall factor of safety

CRF = creep reduction factor (depends on type of polymer, duration of service life, temperature, etc.)


Immersion of geosynthetic samples in a chemical environment to study the chemical/environmental degradation factor


Source: IGS

Reference Geosynthetic Tensile TestsReference Geosynthetic Tensile Tests

6/59Reinforced Soil Walls - 6

Courtesy: Prof R.J. Bathurst, Royal


Military College of Canada

Wide‐width strip tensile test resultsD 4595 ‐ 86

Specimen gauge length = 200 mm

Tult = ultimate tensile strength

Rate of displacement equivalent to 10% strain/min

Courtesy: Prof R.J. Bathurst, Royal


Military College of Canada

Long‐Term Design StrengthLong Term Design Strength

FS = 1.25 to 1.5 (typical)

To take care of uncertainties in quality of the material and manufacturing defects etcmaterial and manufacturing defects, etc.


Default Values for Partial Factors of SafetyDefault Values for Partial Factors of Safety

Guidelines for Design, Specification, and Contracting of Geosynthetic Mechanically Stabilized Earth Slopes on Firm Foundations, Berg 1993

partial factorpartial factor

installation damage 3.0

creep 5.0p

chemical degradation 2.0

biological damage 1.3

joint/seam 2.0


TTa

Tultult


Determination of partial factor for creep

f l hFSCR = ratio of Tult to creep‐limiting strength

Constant load creep testing



Determination of FSCRExample from in‐isolation creep rupture of a woven polyester

id

4500

5000

geogrid

Tult

y = ‐93.18Ln(x) + 4210

3500

4000

4500

y = ‐89.462Ln(x) + 4104.8

2000

2500

3000

oad(lb

/ft) T75 years

FS = T

1000

1500

2000

lo FSCR = TultT75 years

0

500

0.0001 0.001 0.01 0.1 1 10 100 1000 10000 100000

l d ti (h )1000000

FSCR = 1.67

114 yearselapsed time (hrs)


Courtesy: Prof R.J. Bathurst, Royal Military College of Canada

1.20

1.00

CREEP CURVES SS20 : 5 bars x 6 ribs

8.1 kN/m

0.60

0.80

rain

(%)

___ experimentpredicted (TRF)

0.40

str - - - predicted (TRF)

6.0 kN/m

0.00

0.20

4.3 kN/m

6.0 kN/m

Creep testing of geosynthetics

Typical creep test data of geosynthetics

0 2000 4000 6000time (hours)

Creep testing of geosynthetics

00 5 10 15 20 25

Strain%

-1

-3

-2

/mm

)

43 1 (kN/m)

5

-4

n ra

te(%

stra

in/ 43.1 (kN/m)

40.2

-6

-5

Stra

in

T 80 kN/

-8

-77.1 28.514.3

Sherby Dorn plot between strain rate and strain

Tindex = 80 kN/m


8 Sherby-Dorn plot between strain rate and strain

Standard Test Method for Accelerated Tensile Creep and Creep-Rupture of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal MethodMethod



TU-40 geogrid at 68% load level in SIM test

8.6

8.5

8.4

stra

in (

%)

8.3

8.20 2000 4000 6000 8000 10000 12000

time (seconds)


time (seconds)

room temperature Temp = 45 deg. Temp = 59 deg. Temp = 73 deg. Temp = 87 deg. Temp = 95 deg.

Installation damageInstallation damage

ASTM D 5818‐95 ASTM 4595‐86 and FederalASTM D 5818 95, ASTM 4595 86 and Federal Highway Administration guidelines (Publication No FHWA NHI‐00‐044 dated March 2001)No. FHWA NHI 00 044 dated March 2001).


90

100

Project‐specific aggregate

50

60

70

80

Pass

ing

10

20

30

40

%

Place steel plates00.01 0.1 1 10 100 1000

Particle Size (mm)

Place steel plates

Place aggregate base layer Place geosynthetic samples

21Reinforced Soil Walls ‐ 6

Place cover aggregateCompact aggregate using project‐specific compaction equipmentPlace cover aggregate specific compaction equipment

Exhume samples22Reinforced Soil Walls ‐ 6

Publication No. FHWA NHI‐00‐044Publication No. FHWA NHI 00 044

A total of 6 control (virgin) specimens are testedA total of 6 control (virgin) specimens are tested (e.g ASTM 4595‐86).

A minimum of 9 exhumed specimens are required to be tested.required to be tested.

A maximum of 18 tests is required if theA maximum of 18 tests is required if the coefficient of variation from the first 9 tests is greater than 5%.greater than 5%.


CONTROL: Specimen Peak Load Peak Load

No. (N) (kN/m) 1 19752 109 7

EXHUMED: <150 mm crushed stone Specimen Peak Load Peak Load

No. (N) (kN/m) 1 17813 99 01 19752 109.7

2 20884 116.0 3 18839 104.7 4 18972 105.4 5 20067 111.5 6 19243 106 9

1 17813 99.02 17776 98.8 3 17078 94.9 4 17040 94.7 5 16922 94.0 6 18738 104 16 19243 106.9

Mean 19626 109.0 Std. Dev. 773

Coef. of Var. 3.94

6 18738 104.17 18823 104.6 8 17030 94.6 9 18217 101.2

Mean 17715 98.4 Std Dev 750Std. Dev. 750

Coef. of Var. 4.23

RFID = 109.0/98.4 = 1.11

Courtesy: Prof R J Bathurst RMC


Courtesy: Prof R.J.Bathurst,RMC


Courtesy: Prof R.J. Bathurst, RMC

Standard Test Method for Determining Connection Strength Between Geosynthetic Reinforcement andStrength Between Geosynthetic Reinforcement and Segmental Concrete Units (Modular Concrete Blocks)


hydraulic jack to apply l di f

y j pp yvertical load on bricks

loading frame

jack to pull geogrid

geogrid

load cell

blocks

geogrid

a. sectional view of apparatus

load cellload cell

roller grip

b. plan view

L b t t t f ilit f ll t/ ti t t


Laboratory test facility for pullout/connection tests

Connection test between modular blocks and a uniaxial geogrid


Openings filled with stone aggregate – drainage blanket


Close-up of the test arrangement for connection strength tests – LVDT in the picture

Connection loads at serviceability limit of 20 mm

80

90

50

60

70

kN/m

)

30

40

50

pullo

ut lo

ad (k

10

20

p

00 20 40 60 80 100 120

normal load (kN/m)


GX-40 GX-80 GX-100 GX-130

Ultimate limit state connection load capacity

90

100

60

70

80

/m)

40

50

60

lout

load

(kN

/

10

20

30pul

0

10

0 20 40 60 80 100 120normal load (kN/m)


normal load (kN/m)

GX-40 GX-80 GX-100 GX-130

Connection strength test between geogrid and facing panel through positive connection – 8 mm HYSD hooks and 16 mm diameter


pHYSD cross-bar

Arrangement at the front end ith load cell and roller connection


Arrangement at the front end with load cell and roller connection

geogrid

Normal pressurefacing panel

lsand fill loop

connector rod

sand fill

Schematic of the connection capacity test – rigid p y gconnection at both ends


Normal pressurei l

geogrid

pfacing panel

loop

connector rod

sand fill

connector rod

Schematic of test set up to determine the strength due to overlap


Data from connection tests on a geogrid withData from connection tests on a geogrid with Tindex=60 kN/m

Sl. No. Normal pressure Connection type Maximum connection capacity & mode of failure (kN/m)( )

1 12.5 kPa Frictional with lap length of 1.3m 20.6 (pullout/partial rupture)

2 24.5 kPa Frictional with lap length of 1.3m 31 (pullout/partial rupture)p )

3 75 kPa Frictional with lap length of 1.3m 54 kN/m (rupture) 4 75 kPa Clamped connection at both ends 55 kN/m (rupture)


Connection tests on geogrid with Tindex=350 kN/m

Sl N N l C i M i i

Connection tests on geogrid with Tindex 350 kN/m

Sl. No. Normal pressure

Connection type Maximum connection capacity & mode of failure (kN/m)

1 54.5 kPa Frictional connection (300 mm wide l 1 3 l l th)

148.9 kN/m ( ll t/ ti l t )sample, 1.3 m lap length) (pullout/partial rupture)

2 75 kPa Frictional connection (300 mm wide sample, 1.3 m lap length)

212.4 kN/m (pullout/partial rupture)

3 75 kPa Both ends clamped (300 mm wide l )

322 kN/m (rupture) sample)

4 103.5 kPa Clamped at both ends (300 mm wide sample)

325 kN/m (rupture)


Standard Test Method for Measuring Geosynthetic Pullout Resistance in SoilGeosynthetic Pullout Resistance in Soil

• Minimum embedment length of sample = 610 mmMinimum embedment length of sample 610 mm• Minimum Length/width ratio = 2• Minimum depth of soil above and below the

reinforcement = 150 mmreinforcement = 150 mm• Rate of pullout displacement = 1 mm per minute



Interpretation of data from pullout tests on geogrids

P

resistance forcestests on geogrids

P

Le=anchorage length=1.5 m tan2 BLP ev

Sl. No.

Vertical pressure

Peak pullout

Interface friction

=tan/tan

(kPa) load (kN)

angle

1 10.75 kPa 25.9 46.9 >1 1.0 2 3 4

21.6 kPa39.7 kPa 75.9 kPa

41.576.5 127.8

40.5 40.6 36.8

0.92 0.92 0.81


Testing of Vertical Plate Anchors

Materials – Anchor ReinforcementsStrip

Angles Bolts

Plan

Anchor Strip Size (mm) Angle Size (mm)

Side View Plan

Type

Type I 40 (width) x 5 (thick) and 1500 (length)

50 x 50 x 5 (thick) and 150 (length)

Type II 70 (width) x 5 (thick) and 1500 (length)

130 x 130 x 12 (thick) and 350 (length)

Top view of the steel strip and anchor at endTop view of the steel strip and anchor at end

steel strip

Test series

• Tests were first performed on steel strip alone

• Tests on steel strip and anchors were performed at different normal pressures

• Pullout load applied until about 100 kN maximum load or until peak load

• Measured data includes: Load, front and rear displacements and strains developed in the steel strip

Pullout behaviour of steel strip alonep

8

4

6

forc

e, k

N

2

4

pullo

ut f

length of embedment in soil = 1.2 mDepth of embedment = 0 4 m

070 mm wide strip under 100 kPa pressure

Depth of embedment = 0.4 m

0 20 40 60displacement, mm

Displacement Vs Pullout Force relationship for Type I Anchors

80Pullout Vs Normal Pressure

(Type I Anchors)

60

(Type I Anchors)

12 kPa

25 kPa

50 kPa

100 kPa

40

t For

ce, k

N

150 kPa

20

Pullo

ut

0

0 20 40 60 80Displacement, mm

0

Pullout behaviour of Type 2 anchors

120

100

60

80

ut F

orce

, kN

40Pullo

u

Pullout Force Vs Normal Pressure (Type II (large) Anchors)

12 kPa

25 kPa

0

20 25 kPa

50 kPa

100 kPa

0 20 40 60 80Displacement, mm

BS 8006-1995 formula for pullout capacity of anchored reinforcement elementsreinforcement elements

vaapevsasu tBKLBPPP 42

Ps = skin friction force

Pa = passive capacity due to anchora p p y

v=normal pressure

Bs = width of strip

Le = embedment length of steep strip

Ba, ta = width and height of anchor

K = passive pressure coefficientKp = passive pressure coefficient

Pullout factor for plain steel strip at 100 kPa pressue

Pullout displacement (mm)

Load (kN) Pullout factor

20 6 3 0 382040

6.37.1

0.380.42

Pullout factor is higher at lower normal pressures

Comparison of results with Type-I anchors with BS 8006 formula and others

60Comparison Type I Anchors

formula and others

40NExperimental 20 mm

Experimental 40 mm

BS 8006

Das B M40

ut F

orce

, kN

20Pullo

u

0

0 50 100 150Normal Stress, kPa

Comparison of results with Type-II anchors with BS 8006 formula and othersformula and others

60.00 BS 8006:1995

Experimental Values (40 mm displacement)

Experimental Values (20 mm displacement)

Neely's method (Das B M 1990)

40.00

ut F

orce

, kN

20.00Pullo

u

0.00 25.00 50.00 75.00 100.00

0.00

Normal Stress, kPa


Steel mesh with a concrete block anchorSteel mesh with a concrete block anchor

Pullout tests on welded mesh with d ffdifferent connections

Working load

Limiting displacement

Connection Capacity

Working load (kN)

Limiting displacement ( )

Connection Capacity (kN) load

(kN) displacement (mm)

Capacity (kN)

40.00 20.00 40.5

(kN) (mm) (kN)40.00 20.00 28.8 40.00 20.00 21.0



Typical connection failures observed in laboratory tests

Documents

Reinforced soil walls-6 · (()kN/m) 1 12.5 kPa Frictional with lap length of 1.3m 20.6 (pullout/partial rupture) 2 24.5 kPa Frictional with lap length of 1.3m 31 (pullout/partial