complete aspects of deflection basin parameters in mechanistic det , horak emile, 187 tesis doctoral...

8/18/2019 Complete Aspects of Deflection Basin Parameters in Mechanistic Det , Horak Emile, 187 Tesis Doctoral en Ingles, Ojo

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ASPECTS OF DEFLECTION BASIN

PARAMETERS USED IN A MECHANISTIC

REHABILITATION DESIGN PROCEDURE FOR

FLEXIBLE PAVEMENTS IN SOUTH AFRICA

HORAK, E

PhD (Civil Engineering)

University of Pretoria

1987


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ME A S UR E ME NT A ND DA T A P R OC E S SI NG OF DE F L E C T I ON B AS I NS I NSOUTH AFRI CA

A NA L Y S I S OF DE F L E C T I ON B AS I NS ME A S UR E D DUR I NG A CC E L E R AT E D T E ST I NG

L I T E R AT U RE S UR VE Y ON MA T E RI A L C HA RA CT E R I Z AT I ON A NDS T R UC T UR AL A NA L Y S I S US I NG DE F L E C T I ON B AS I NS

E F F E C T I V E E L A S T I C MODUL I DE T E R MI NE D F R OM R OA D S UR F A CEDEF L ECTOMETE R MEASUREMENTS

R E L A T I ONS HI P S B E T WE E N DI S T R E S S DE T E R MI NA NT S A NDDE F L E CT I ON B AS I N P ~l E T ERS : A L I T E RA TURE S URV EY

R E L A T I ONS HI P S B E T WE E N DE F L E C T I ON B AS I N P A RA ME T E R S A NDDI S T R E SS DE T E R MI NA NT S F OR T Y P I C AL S OUT H A F R I C AN P A V E ME NT S

P R OP OS E D US E OF DE F L E C T I ON B AS I N ME A S UR E ME NT S I N T HEMECI Dl ~I ST I C REHABI L I TATI ON DES I GN OF FL EXI BLE PAVEMENTS

CRACK MOVEMENT CALCULATI ONS WI TH DEFL ECTI ON BAS I NMEASUREMENTS ON N4/ 3


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ASPECTS OF DEFLECTI ON BASI N PARAMETERS USED I N AMECHANI STI C REHABI LI TATI ON DESI GN PROCEDURE FOR FL EXI BLE

PAVEMENTS I N SOUTH AFRI CA.

CI VI L ENGI NEERI NG

PHI LOSOPHI AE DOCTOR ( CI VI L ENGI NEERI NG )

Th e no n- de s t r uc t i ve mea s ur ement of de f l ec t i on ba s i ns ha s c ome a l ong way

f r om meas ur i ng on l y max i mum def l ec t i on or r ad i us o f c ur v at ur e and us i ng

empi r i cal r e l at i onshi ps i n r ehabi l i t at i on desi gn. New equi pment was

devel oped wor l d - wi de and anal y s i s t ec hni ques mov ed t owar ds ut i l i s i ng t he

f u l l def l ec t i on bas i n i n f undament a l anal y s i s pr oc edur es .

Th i s aut ho r add r es s ed t he pr obl em of a pr ope r de s c r i pt i on of t he f u l l

d ef l e c t i o n b as i n b y d oi n g a d et a i l e d l i t e r a t u r e s u r v e y o n t h i s s u bj e c t .

Var i ous def l ec t i on bas i n par amet er s t hat des c r i be t he def l ec t i on bas i n

ar e l i s t ed, as wel l as t he v ar i ous meas ur i ng appar a t us r e l a t ed t o t hem.

The app ar at us ar e al l di s c us s ed i n de t a i l and r e l at ed t o t he equ i pment

av ai l ab l e i n Sout h Af r i c a .

The meas ur e ment of de f l ec t i on ba s i ns wi t h t he r oad s ur f a c e de f l ec t omet er

( RSD) under ac c e l er a t ed t es t i ng wi t h t he f l eet o f heav y v ehi c l e s i mul a -

t o r s ( HVSs ) ar e des c r i bed i n det a i l . An i mpr ov ed dat a mani pul a t i on

p r o c ed ur e i s p r o po s e d wh i c h s i mp l i f i e s t h e c a l c u l a t i o n o f a l l t h e

def l ec t i on bas i n par amet er s f ound i n l i t e r a t ur e . Var i ous model s t o f i t

t h e me as u r e d d ef l e c t i o n b as i n s a r e a l s o i n ve s t i g at e d i n a n e f f o r t t o

d es c r i b e t h e d ef l e c t i o n b as i n i n f u l l t o o.

The meas ur ed de f l ec t i on ba s i n pa r amet er s of a bi t umen, gr anu l ar ,

c e me nt e d a nd l i g ht s t r u c t u r e d g r a nu l a r b as e p av e me nt a r e d i s c u s s e d i n

d et a i l a s b ei n g t e s t e d wi t h t h e f l e et o f HVS ' s . I t i s s h own h ow t h e

def l ec t i on bas i n par amet er s r e f l ec t t he s t r uc t ur a l c apac i t y o f t he

v a r i o us l a y er s a nd b eh av i o ur s t a t e s . A mo r e a c c ur a t e d es c r i p t i o n o f t h e

b eh av i o ur s t a t e s i s ma de p os s i b l e wi t h t h e p r o po s a l o f r a ng es f o r t h e

v a r i o us b eh av i o ur s t a t e s f o r t h es e d ef l e c t i o n b as i n s s e l e c t e d.


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A l i t e r a t u r e s t u dy wa s ca r r i e d o ut t o i n ve st i g a t e t h e va r i o us a n al ys i s

p r o c e du r e s t h at u s e me as u r e d d ef l e c t i o n b as i n s a s b as i c i n pu t i n t h e

c h ar a c t e r i z a t i o n o f ma t e r i a l s . On t h e b as i s o f t h i s s t u dy . l i n ea r

e l a st i c p r o g r a mme s we r e u se d t o ca l cu l a t e e f f e c t i ve e l a st i c mo d ul i f o r

e a c h p a veme n t l a ye r . u s i n g me a su r e d d e f l e c t i o n b a s i n s a s i n pu t .

The po s s i bi l i t y t o r e l at e t y pi c al di s t r e s s de t e r mi na nt s t o meas ur ed

d ef l e c t i o n b a s i n s we r e i n ve st i g at e d i n t h e l i t e r a t u r e . Ba se d o n t h i s .

t yp i ca l S o ut h Af r i ca n f l e x i b l e p a veme nt s t r u c t u r e s we r e a n al yse d

me c h a ni s t i ca l l y a n d t yp i ca l d es i g n cu r ve s we r e e st a b l i sh e d f o r t yp i ca l

b i t u me n a n d g r a n ul a r b a se p a veme n t s . T h e e f f e c t o f o ve r l a ys we r e i n ve st i -

g at e d t o o. r e s u l t i n g i n t y p i c a l o v er l a y d es i g n c u r v e s .

I n t h e f i n a l ch a pt e r t h e a u t h o r e n de a vou r s t o su mma r i se t h e r e se a r ch b y

i n di c a t i n g h o w d e f l e c t i o n b a s i n s ca n b e me a su r e d a n d e n ha n ce t h e S o ut h

Af r i ca n me ch a ni s t i c r e h ab i l t a t i o n d e s i g n p r o ce ss . On l y t h e l a t t e r

r e h ab i l i t a t i o n d es i gn p r o ce d ur e i s d i sc u sse d wi t h sp e c i f i c r e f e r e n c e t o

t he enhancement of t he behavi our st at e i dent i f i cat i on. mat er i a l

ch a r a c t e r i za t i o n . a n al ys i s p r o ce d ur e a n d r e h ab i l i t a t i o n d e s i g n wi t h

me as u r e d d ef l e c t i o n b as i n p ar a me t e r s . T he a ut h or e nd s o f f b y g i v i n g a n

i n di ca t i o n o f t h e f u t u r e r e se a r ch n e ed i n t h i s f i e l d o f d e f l e c t i o n

b a s i n s .


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ASPEKTE VAN DEFL EKSI EKOM- PARAMETERS GEBRUI K I N ' N MEGA-NI STI ESE REHABI LI TASI E- ONTWERPPROSEDURE VI R BUI GBAREPLAVEI SELS I N SUI D- AFRI KA.

SI VI EL E I NGENI EURSWESE

PHI LOSOPHI AE DOKTOR ( SI VI ELE I NGENI EURSWESE )

Di e ni e- dest r ukt i ewe met i ng van def l eks i ekomme het ' n l ang pad gevor der

v anaf d i e met i ng v an s l egs maks i mum def l eks i e o f k r ommi ngs t r aa l en d i e

gebr ui k van empi r i ese ver bande i n r ehabi l i t as i e- ont wer p. Nuwe t oer ust i ng

i s we r e l d wy d o nt wi k k e l e n a na l i s e t e gn i e k e h et i n d i e r i g t i n g v a n d i egebr ui k van di e hel e def l eks i ekom i n meer f undament el e anal i sepr osedur es

beweeg.

Hi e r d i e o ut e ur s p r e ek d i e p r o bl e em v a n d i e v o l l e di g e b es k r y wi n g v a n d i e

def l eks i ekom aan deur ' n d i epgaande l i t e r a t uur s t udi e oor h i er d i e

onder wer p t e doen. Ver skei e def l eks i ekom- par amet er s wat di e def l eks i ekom

b es k r y f . wo r d g el y s . s o we l a s d i e o nd er s k e i e a pp ar a t e wa t d aa r me e

v e r b an d h ou . Hi e r d i e a pp ar a t e wo r d a l ma l i n d et a i l b es p r e ek e n i n

v er band gebr i ng met d i e t oer us t i ng wat i n Sui d - Af r i ka bes k i kbaar i s .

Di e met i ng van def l eks i ekomme met di e padopper vl akt e- def l ekt omet er ( POD)

onder ver snel de t oet s i ng met di e v l oot van swaar voer t ui gnaboot ser s

( SVN' e) i s i n det a i l beskr yf . ' n Ver bet er de dat amani pul as i e- pr osedur e

i s v oor ges t e l wat d i e ber ekeni ng v an a l d i e def l eks i ekom- par amet er s v er -

eenv oudi g s oos gevi nd i n d i e l i t e r a t uur . Ver s ke i e model l e wat gebr u i k i s

o m di e g eme t e d ef l e k s i e k om t e p as . i s o nd er s o e k i n ' n p og i n g o m d i e

def l eks i ekom t en v o l l e t e bes kr y f .

Di e gemet e def l eks i ekom- par amet er s van ' n bi t umen. gebr eekt e k l i p.

ges ement eer de en l i g t e s t r ukt uur kor r e l k r oonl aag- p l av e i s e l i s i n det a i l

b es p r e ek s o o s g et o et s me t d i e v l o ot S VN' e . Da ar i s g et o on h oe d i e

def l eks i ekom- par amet er s di e st r ukt ur el e kapasi t e i t van di e onder skei e

l a e e n g ed r a gs t o es t a nd e r e f l e k t e er . ' n Me er a k k ur a t e b es k r y wi n g v an d i e

gedr ags t oes t ande i s moont l i k gemaak deur d i e daar s t e l l i ng v an gr ens e

v i r d i e v er s k i l l ende gedr ags t a t e v an d i e ges e l l ekt eer de def l eks i ekom-

par a met er s .


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' n L i t e r a t uur s t ud i e i s gedoen om d i e v er s k i l l ende anal i s e - pr os edur es wat

v an def l eks i ekom- par amet er s as bas i es e i ns et gebr u i k maak, i n d i e

kar akt er i s er i ng v an mat er i a l e , t e onder s oek. Op gr ond v an h i er d i e s t ud i e

i s daar ook gepoog om gebr u i k t e maak v an l i n i eer e l as t i es e pr ogr amme

o m e f f e k t i e we e l a s t i e s e mo du l i t e b er e k en , v i r e l k e p l a v ei s e l l a ag , v a na f

gemet e def l eks i eko mme.

Di e moont l i khei d om det er mi nant e v i r oor spannendhei d di r ek aan gemet e

def l eks i ekom- par amet er s t e kan koppel , i s i n d i e l i t e r a t uur nagev or s . Op

h i e r d i e t r a nt i s d aa r t o e t i p i e s e S ui d - Af r i k a an s e s o e pe l p l a v ei s e l -

st r ukt ur e megani st i es ont l eed en sogenaamde ont wer pkur wes daar gest el v i r

t i p i es e b i t umen- en kor r e l k r oonl aag- p l av e i s e l s . Di e i nv l oed v an

her dek l ae i s ook onder s oek en t i p i es e her dek l aag ont wer pkur wes i s

daar gest el .

I n d i e f i n al e h oo f s t u k p oo g d i e s k r y we r o m di e n av o r s i n g o p t e s o m de ur

aan t e dui hoe def l eks i ekomme gemeet kan wor d en d i e Sui d - A f r i kaans e

megani s t i es e r ehabi l i t as i e ont wer p- pr os edur e kan v er s t er k . S l egs l aas ge-

noemde r ehabi l i t as i e ont wer p- pr os edur e i s bes pr eekmet s pes i f i eke

ver wysi ng na hoe gemet e def l eks i ekom- par amet er s di e gedr agst oest ande kan

i dent i f i s eer , mat er i a l e kar akt er i s eer , d i e anal i s e pr os edur e en r ehabi -

l i t a s i e o nt we r p k a n v e r s t e r k . Di e o ut e ur e i n di g d eu r a an t e d ui wa t d i e

nav or s i ngs behoef t e i n d i e t oekoms i s t en ops i gt e v an def l eks i ekomme.


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I t hank my f r i end and L or d J es us Chr i s t f o r s et t i ng me f r ee t o bec ome

t he per s on He want s me t o be. May t h i s t hes i s a l s o c ont r i but e t o Hi s

gl or yl

Th e Chi ef Di r e c t or of t he NI T RR, Mr R N Wal ker , i s t han ked f o r t he

per mi s s i on t o us e t h i s r es ear c h wor k done at t he I ns t i t u t e i n t h i s

t hesi s .

I t hank Dr Char l es F r eeme, f o r mer gr oup head o f t he P avement Engi neer i ng

Gr oup, f o r h i s ent hus i as t i c s uppor t and mot i v at i on by ex c el l ent ex ampl e .

I n t he s ame br eat h I woul d l i ke t o t hank P r o f es s or Car l Moni s mi t h f r om

U. C. Ber ke l ey , who i n i t i a t ed my i n t er es t i n t h i s f i e l d .

I t hank t he whol e f o r mer P avement Engi neer i ng Gr oup f o r t hei r k i nd

c o - o pe r a t i o n a nd i n t e r e s t . Ra s s i e Ot t e i s s i n gl e d o ut f o r h i s p er s e -

v er a nc e a nd h ar d wo r k o n t h e c o mp ut e r . A s p ec i a l wo r d o f t h an ks t o

Ro l e t t e Sut t on f o r her met i c u l ous edi t i ng. The t y p i ng done by t he t y p i ng

poo l i s h i ghl y appr ec i a t ed.

I wo ul d l i k e t o t h an k my wi f e Ma r i a na f o r h er l o vi n g s u pp or t , a nd

Hel ene, Emi l e , Eduar d and Ane f o r endur i ng t he moods .

L as t o f a l l I wo ul d l i k e t o t ha nk my pa r e nt s , Ma r k i e a nd Be t s , f o r t h ei r

s u pp or t a nd i n t e r e s t o ve r t h e y ea r s . Ma r k i e , I k no w y ou wo ul d h av e b ee n

pr oud I


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CH.APTER 1

A LITERATURE SURVEY ON DEFLECTION BASIN MEASUREMENTS


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PAGE

1 I NTRODUCTI ON 1 . 2

2 DEFL ECTI ON BASI N PARAMETERS 1 . 5

2 . 1 Rev i ew of par amet er s 1 . 5

2 . 2 Eval uat i on of par amet er s 1 . 7

3 DEFL ECTI ON MEASURI NG I . 1 9

3 . 1 Re v i e w o f d e vi c e s a nd me t h od s I . 1 9

3 . 2 E v al u at i o n o f d ev i c e s I . 2 1

3 . 3 Co r r e l a t i o ns bet ween dev i c es I . 3 1

4 CONCL USI ONS AND RECOMMENDATI ONS I . 3 2


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I n t he devel opment of f undament al met hods of pavement eval uat i on by

means of def l ect i on measur ement s i t i s i mper at i ve t hat an accur at e

de scr i pt i on of t he de f l e ct i on ba si n be gi v en. I n t he ma j or i t y of

anal ysi s pr ocedur es onl y t he maxi mum sur f ace def l ect i on (


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IDEFLECTION DIFFERENCE AT OFFSET r

I

Illustration of the same maximum deflection for two different deflec-

tion basins.

FIGURE 1.1

DEFLECTION' BASIN ILLUSTRATION.


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o

- -

8

REAR WHEELS

FRONT WHEEL

b) UNDER A SINGLE REAR AXLE DUAL WHEELTRUCK

FIGURE 1.2

TYPICAL SHAPES OF DEFLECTION INFLUENCE

LI NES (Dehlen ,1962 b)


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Road Congr esses , 1983) . " Ther e ar e obvi ous at t r act i ons i n maki ng

maxi mum use of t he i nf or mat i on t hat can, i n pr i nci pl e, be obt ai ned

by det ai l ed ev al uat i o n o f t he def l ec t ed s hape as i t obv i at es o r

r educ es t he need f o r as s u mpt i o ns about , o r meas ur ement o f ,

pr oper t i es of pavement mat er i al s. "

Thi s i nt r oduc t or y di s cus s i on c l ear l y i ndi cat e t hat t her e i s a need

f or t he measur ement and i nt er pr et at i on of t he f ul l def l ect i on basi n.

As wi l l be di s c us s e d i n l at er c hapt er s , i n So ut h Af r i c a t he f ul l

def l ect i on basi n i s measur ed, but t he anal ysi s hi st or i cal l y f ocussed

on t he smal l ar ea sur r oundi ng maxi mum def l ect i on. I n or der t o make

be t t er use of t he f ul l de f l ect i on ba si n , a l i t e r a t ur e su r v ey wa s

conduct ed. Thi s l i t er at ur e sur vey cover s t he wor k done over seas wi t h

o t her meas ur i ng equi pment des c r i pt i o n met hods o f t he f ul l

def l ect i on basi n , eval uat i on of var i ous def l ect i on basi n par amet er s

a nd de vi ces. I n or de r t o br i ng i t i n l i ne wi t h t he Sout h Af r i ca n

s c ene , al l t hes e di s c us s i o ns ar e r el at ed t o t he pr ac t i c e her e .

Recommendat i ons ar e made by t hi s aut hor t o enhance t he cur r ent

pr ac t i c e and us e o f So ut h Af r i c an dev i c es and def l ec t i o n bas i n

desc r i pt i on.

Sur f a ce de f l e ct i ons a r e ge ne r a l l y me asu r e d by se nsor ( s) of

v ar i ous k i nds l ocat ed i n a f i x ed l i ne a nd nor ma l l y a t a f i x ed

di st ance r el at i ve t o t he cent r i od of t he l oad ar ea. Def l ect i on

basi n par amet er s di f f er i n t hei r r e l at i on t o t he measur i ng

devi ce and degr ee t o whi ch t hey desc r i be t he essent i al f eat ur es

of t he def l ect i on basi n. I n Tabl e 1. 1 a summar y i s gi ven of t he

par amet er s, f or mul ae, t est met hod or devi ce nor mal l y ass oci at ed

wi t h i t and at l east one r ef er ence.

I t i s s ugges t ed t hat t he f ol d- i n o f T abl e 1. 1 at t he bac k be

f o l de d out t o ensu r e e ase of r e adi ng a s e xha ust i v e r e f e r e nce

wi l l be made t o t he var i ous def l ect i on basi n par amet er s i n t he

sect i ons t o f ol l ow, as wel l as t he chapt er s t o f ol l ow.


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Parameter Formula Measuring device Reference

I. Maximum 80 Benkelman beam KennedYl et at

deflection Lacroix deflectograp, Asphalt Institute( 197

2. Radius of r 2 Curvaturemeter Dehlen (1962 a)R=curvature 280(80/8r- 1)

r = 127 mm

3. Spreadability [(80+81 +82+8;y/5]100 Dyna f lect Vaswani (1971)S=

80

81

• • • • 83spaced 305 mm

4. Area A = 6 [I + 2 (8/8~ + 2 Falling weight Hoffman and

(82180) + 83/80 ] deflectometedFWD) Thompson (1981)

5. Shape factors F, = (80 - 82) I 8 1 FWD Hoff man and.

F2= (8 I - 83) I 82 Thompson (1981)

6. Surface SCI = 80-8r i where Benkelman beam Anderson (1977)

curvature r = 305 mm Road rater Kilareskilat a1.(1982)

index or r = 500 mm FWD Molenaar (1982)

7. Base curvature BCI = 8610- 891~ Road rater Kilareskilet al.(/982)index

8. Base damage BD! = 8305 - 8610 Road rater Kilareski,et aL(1982index

9. Deflection Or = 8r 180 where FWD Claessen and

ratio ar~ 80/2 Ditmarsch (1977)

10.Bending BI • 8 la where Benkelman beam H veem (1955)

Index a • Deflection basin

II. Slope of SD= tan-1 (80 - 8r)/r Benkelman beam Kung (1967)

deflection where r = 610 mm

12.Tangent ST = (So - 8r ) I r Benkelman beam University of slope where r is determined FWD Dundee (1.980)

by a polynomial function

13.Radius of RI =R'/80 where R' is the Ford andinfluence distance from 80 to where Bissett ( 1962)

basin is tangent to horizon.


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The f i r s t t wo par amet e r s l i s t ed i n Tabl e 1. 1 ar e t he t r adi t i ona l

maxi mum def l ect i on and r adi us of cur vat ur e. Thei r f or mul as show

t hat onl y t he s mal l a r e a s ur r oundi ng ma xi mum def l ec t i on

( po s i t i v e c ur v at ur e ) i s ut i l i z e d. T he s pr e adi bi l t y ( 5) a nd a r e a

( A) par amet er s obv i ous l y c ov er t he f ul l def l ec t i on bas i n.

Par a met er s s uc h as t he s hape f ac t or s ( F 1 and F 2) , s ur f ac e

curvat ure i ndex ( 5CI ) , base damage i ndex ( BDI ) , base curvat ure

i ndex ( BCI ) , s l o pe o f def l e ct i o n ( 5D) a nd t a nge nt s l o pe ( 5T )

a l s o c o ve r mo r e t ha n o nl y pa r t o f t he a r e a o f po s i t i v e c ur v at ur e

near t he l oad. I n f act some of t he af or ement i oned par amet er s t r y

t o de s c r i be e i t her t he a r e a o f po s i t i v e c ur v at ur e o r t he a r e a o f

r e ve r s e c ur v at ur e o r t he i mpor t a nt a r e a s ur r o undi ng t he poi nt o f

i nf l e ct i o n whe r e t he po s i t i v e c ur v at ur e c ha nge s t o t hat o f t he

r ever s e c ur vat ur e. The ot her par amet er s not ment i oned, do

descr i be t he def l ect i on basi n bet t er t han maxi mum def l ect i on and

r adi us of c ur vat ur e, but i t i s not c l ear i n whi c h ar ea of t he

def l ect i on basi n t hey f al l wi t h t hei r descr i pt i on.

The Techni cal Commi t t ee Repor t on f l exi bl e Roads of t he XVI I

Wor l d Road Congr ess ( Permanent I nt er nat i onal Ass oci at i on of Road

Congr es s es , 1983) s t at es ; " T he t r ans i ent di s pl ac ement or

def l ec t i on of t he r oad s ur f ac e r epr es ent s t he s um o f al l t he

ver t i cal st r ai ns i n t he pavement and subgrade and r emai ns t he

mos t wi del y us e d meas ur ement of s t r uc t ur al c ondi t i on. I t s

advant ages ar e, t he r el at i ve si mpl i ci t y of t he measur ement s, t he

l a r ge a mo unt o f e xpe r i me nt a l da t a t ha t a l r e ady e xi s t s a nd t he

s t r o ng c o r r e l a t i o n f o und be t we en de f l e c t i o n a nd o ve r a l l per -

f or ma nc e i n wel l def i ne d c ondi t i ons . I t i s howev er not v er y

r esponsi ve t o changes i n t he st i f f ness of upper pavement l ayer s

and i s not a uni que measur ement of per f ormance on al l t ypes of

pavement . "

A sensi t i v i t y anal ysi s done at t he Uni ver si t y of Dundee ( 1980)

i nc or por at ed mos t of t he par amet er s l i s t ed i n Tabl e 1. 1. A

t hree- l ayered pavement syst em was anal ysed. Al l t he st r uct ural

par a me t e r s we r e v ar i e d. T he s e ns i t i v i t y a na l y s i s wa s do ne by


16/312

I r r espect i ve of t he t echni que or measur i ng devi ce, t he par a-

me t e r s , be ndi ng i ndex ( BI ) a nd r a di us of i nf l ue nce ( RI ) a r e

di f f i c ul t t o det er mi ne. Thi s i s due t o t he f ac t t hat t he

l engt h of t he def l ect i on basi n i s nor mal l y t oo l ong t o measur e

accur at el y i n si t u. The val ue of maxi mum def l ect i on ( 0 ) waso

f ound t o be unr el i abl e when used al one owi ng t o t he di f f er ence

i n pa ve me nt condi t i ons. Thi s conf i r ms t he i l l ust r a t i on i n

Fi gur e 1. 1 and concl usi on by Whi t comb ( 1982) i n Sect i on 1.

Radi us of cur vat ur e par amet er ( R) showed a hi gh sensi t i vi t y t o

most changes i n t he pavement st r uct ur al par amet er s, but wasi nsensi t i ve t o subgr ade el ast i c modul us. The def l ect i on r at i o

( Q or Qr ) and spr eadabi l i t y ( S) showed even l ess sensi t i vi t y t o

changes i n t he ot her st r uct ur al par amet er s. Cont r ar y t o t hi s

c onc l us i o n Koo l e ( 1979) r epor t s t hat t he par amet er Q i s a

r el i abl e par amet er . The i nconsi st ency seems t o st em f r om t he

l ack of adher ence t o Kool e' s ( 1979) pr econdi t i on ( 0 : : : 0/ 2) i n. r 0

det er mi ni ng Q. I t seems t hat usi ng a f i xed val ue of 0r =0610' as

i n t hi s a nal y si s done by t he Uni v er s i t y of Dunde e ( 1980) , ca n

r esul t i n t he r ecor ded i nsensi t i vi t y t o changes i n t he pavement

st r uct ur al par amet er s. I f i t i s t aken i nt o consi der at i on t hat

. t hi s par amet er was devel oped f or a speci f i c t ype of pavement

st r uct ur e, i t i s t o be expect ed t hat var i ances i n st r uct ur e wi l l

def i ni t el y i nf l uenc e i t s s ens i t i v i t y . Rohl f et al . ( 1985)

i ndi cat e t hat spr eadabi l i t y ( S) i s an i ndi cat i on of t he r at i o of

t he sur f ace l ayer t o suppor t l ayer st r engt hs.

I n t hi s sensi t i vi t y anal ysi s by t he Uni ver si t y of Dundee ( 1980)

t he sl ope of def l ect i on ( SD) and t angent sl ope ( ST) have shown a

hi gh sensi t i vi t y t o changes i n t he pavement st r uct ur al par a-

me t e r s . I t i s concl ude d, t hough, t hat t he s l ope of de f l e ct i on

( SD) may have t he same unr el i abi l i t y as t he maxi mum def l ect i on

( 00) when us ed al o ne. T he r eas o n f o r t hi s i s t hat , as i l l us -

t r at ed i n Tabl e 1. 1, a f i x ed v al ue of 0 =0610 i s us ed. Ther

t a nge nt s l ope , on t he ot he r hand, ma ke s use of a pol y nomi al


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f unct i on t o descr i be t he def l ect i on basi n and f orm t he basi s f or

t he s el ec t i on of 6 unambi guous l y. Dehl en ( 1962b) al s or

obser ved t hat R i s dependent mai nl y on t he modul i of t he upper

l ay er s of const r uct i on. a nd v er y - l i t t l e on t hose of t he mat e-

r i al s at dept h. He s t at es t hat ; " T he r adi us of c ur vat ur e of a

r oad su rf a ce unde r a gi v en v ehi c l e i s de pe nde nt ma i nl y on t he

Young Is modul i of t he mat eri a l s i n t he base and subbase; . . . " He

al s o obs er v ed t hat R i s dependent t o a c ons i der abl e degr ee on

t y r e pr es s ur e and onl y t o a l es s er degr ee on t he wheel l oad

whi l e 6 i s dependent on wheel l oad and l i t t l e on t yr e pressur e.o

Hof f man and Thompson ( 1981) devel oped t he ar ea ( A) par amet er

f r o m wor k done by Vas wani ( 1971) . I t i s obv i o us l y r el at ed t o

t he spr eadabi l i t y ( S) paramet er and an at t empt t o i ncor por at et he f ul l def l ect i on basi n.

The s ur f ace cur vat ur e i ndex ( SCI ) i ndi cat es t he s t r engt h of t he

upper por t i on of a pavement accor di ng t o an anal ysi s of st andard

pav ement s t r uc t ur es i n t he St at e of Vi c t or i a, Aus t r al i a by

Anders on ( 1977) . General l y i n t hese pavement st r uct ures, as i n

t he dr y r egi o ns of Sout h Af r i c a, r at her t hi n ( ±50 mm) as phal t

sur f aci ng l ayers are used. I n Anders on' s ( 1977) st udy, maxi mum

def l ect i on ( 6 ) was used si mul t aneousl y t o descr i be t he r esponseo

of t he l ower por t i on of pavement s successf ul l y.

Ki l ar es k i et al . ( 1982) s t at e t hat t he bas e c ur vat ur e i ndex

( BCI ) i ndi c at es t he s t r engt h of t he l ower por t i on of t he

pavement syst em. The basi s f or t hese st at ement s concer ni ng SCI

and BCI c an be s een i n F i gur es 1. 3 and 1. 4 wher e t he r el at ed

s t r uc t ur al par amet er s ar e v ar i ed. I t c an be s een i n F i gur e 1. 3

t hat a di f f er enc e i n def l ec t i o n at 0 and 305 mm ( SCI ) wi l l

r ef l ect t he change i n ba se el ast i c modul us. I n F i gur e 1. 4 t he

di f f er ence i n def l ect i on at 610 mm and 915 mm ( BCI ) wi l l r ef l ect

t he change i n subgr ade el ast i c modul us.

The Techni cal Commi t t ee Repor t on f l exi bl e r oads of t he XVI I

Wor l d Road Congr ess ( Per manent I nt er nat i onal Ass oci at i on of Road

Congr es s es , 1983) c onc l udes on t he def l ec t ed s hape; " T he


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200

-EE 175

'ItI

0

- E,. 6900 MPaz0 150 E, • 3450 MPat-

El • 1380 MPauI . L J..JL & -I . L J

1250..J

<U-t-o : : 100I . L J

>I . L J

U< 75L & -0 ::: : : : >(/)

50 E1 = BASE ELASTICMODULUS

25o 200 400 600 800

DISTANCE FROM LOADING CENTRE (mm)

FIGURE 1.3VARIATION OF SURFACE

DEFLECTION BASIN WITH

SURFACE MODULUS, EI(Kilareski, et 01.,1982)


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FIGURE 1.4

VARIATION OF SURFACE DEFLECTIONBASIN WITH SUBGRADE MODULUS,E4

( K ilareski, et aI., 1982)


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deflected shape near the point of maximum deflection is

sensitive to changes in upper pavement layers and relatively

unaffected by the subgrade. Deflection levels and their rate of

change further from the maximumhave been related to the stiff-

ness of lower pavement layers and the subgrade."

Very interesting information is available on how the various

deflection basin parameters relate to increase in number of

standard axle repetitions. Kilareski et al. (1982) produced the

typical results of deflection versus number of equivalent axle

repetitions as shown in Figure 1.5. SCI (difference between

Sensors 1 and 2) and the BCI (difference between Sensors 3 and

4) are virtually constant with the increase in number of stan-

dard axle repetitions. From this follows the need for thedevelopment of the base damage index (BDI) which is the differ-

ence between Sensors 2 and 3). The values of the BDI change

with the increase in repetitions of standard axles. Figure 1. 6

results from work done by Molenaar (1983); in spite of the

difference in measuring technique and device (see Table 1.1) it

shows considerable support for this approach of relating the

surface curvature index (SCI) to the repetitions of standard

axles.

Rohlf et a10 (1985) did a multivariate analysis of pavement

Dynaflect deflection data. A relationship between Dynaflect

deflections and pavement temperature, subgrade moisture, and

cumulative traffic loading for a number of different pavement

sections was developed. A typical Dynaflect deflection basin

measurement is illustrated in Figure 1. 7. The major conclusion

from this study is that the base thicknesses and base layer

elastic moduli had significant effects on the sensor deflec-

tions. The first sensor deflection (maximum) was directly

related to the base thickness.

Tam (1985) ana lysed three-, four- and five-layered pavement

structures and determined how the variation of structural inputs

affected the deflection basin. Figure 1 . 8 summarizes the

relative importance of the effect of varying the stiffnesses of


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- TEST SECTION 1cz 1,500

SENSORS SPACED AT 305 mm0..0

-z1,000

I-

ul.L J..Jl.L

l .L J 0,500

3

4

0 0,5 1,0 1,5 2,0 2,5 3,0( EAL Millions)

FIGURE 1.5

CORRECTED ROAD RATER SURFACEDEFLECTIONS VS. IS-KIP (SO kN)

EQUIVALENT SINGLE - AXLE LOAD

(Kilareski,et 01., 19S2)


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107

(j)

W...J

X

~~ 10

6

Zw...J

~-: : >0w

10~l1..0

a : : :wC D

::: : >10

4z

FIGURE 1.6

EXAMPLE OF A PAVEMENT DESIGN

CURVE BASED ON THE SURFACE

CURVATURE INDEX (SC I) (Molenoor,1983)


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1 2 "

20"

LOADINGWHEELS

ORIGINAL

SURFACi

48"

~ • . . . • .

" - " -" - . . . . . . .

. . . . • • . .-

W I

(O M O ) W2

W3 W4

'--- DEFLECTEDSURFACE

seI

FIGU RE I. 7

DYNAFLECT DEFLECTION BASIN (Rohlf, at 01.,1985)


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DISTANCE FROM LOAD CENTRECm)

o 0,3 0,6 0,9 1,2 1,5 1,8

STIFF

SUBGRAOE

Ewe: 4000

EB :10000,> < ,

""ESG : 110

Ewe: 4000

EB : 10000JX< M<

ESG

: 30

Ewe: 4000

EB : 14000

A< ,"",E

SG: 50

Ewe: 4000

E B : 4000>x < ,,,,,

ESG : 50

All units in MPa for stiffness modulus,Eused in each layer

FIGURE 1.8

RELATIONSHIP BETWEEN VARIATION OFSTIFFNESS MODULI IN BASE LAYER AND

SUBGRADE ( Tam, 1985)


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t he base l ayer and t he subgr ade i n a t hr ee- l ayer ed pavement

s t r uc t ur e. The mai n c onc l us i ons f r om t he Tam s t udy on

t hr ee- l ayer ed pavement s t r uct ur es ar e as f ol l ows :

( a) The var i at i on of base l ayer t hi ckness had t he gr eat est i nf l uence

on maxi mum def l ect i on ( < 5 ) a nd sp r e ada bi l i t y ( S) . Thi s wa so

f ol l owed by t he s ubgr ade s t i f f nes s and bas e s t i f f nes s .

Spr e ada bi l i t y ( S) ha d se ve n de f l e ct i ons i ncor por a t e d i n t he

cal cul at i on i nst ead of t he nor mal f i ve ( see Tabl e 1. 1) .

( b) As t he su bgr ade st i f f ne ss i ncr e ase s ( de cr e ase s) , ma xi mum

def l ect i on (< 5 ) and spr eadabi l i t y ( S) decr ease ( i ncr ease) ( seeo

Fi gur e 1. 8) .

( c) The i ncr ease ( decr ease) i n magni t udes of pavement st r uct ur al

par amet er s r educes ( i ncr eases) maxi mum def l ect i on (


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REFERENCESTRUCTURE --lEwc=4000 MPa, u =0, 4 hwc=40mm

Ee = 1000 MPa, u =0,4 1 , · 2 0 0 0 ' 0 'Ese =100 MPa, u = 0,3 hse=200mm

1 : : < . " : /A

ESG= 50 MPa, u =0,4

80 = 431,.,.m, S = 0,678

2,5 • 2,5 •LUUZLU

0:IJJ 2,0lL .LU

0:

J:LU

1,5 1,51- 0:

V -::>31-

og- 0:t:il- 1,0 1,0

h / 1 E S B0: CJ )

0:

~~LUI-

hse EseLU 0,5 0,5:E< X Ee

E e0:< XQ.

0 00,4 0,6 0,8 1,0 1,2 1,4 1,6 0,8 1,0 1,2

MAX. DEFLECTION RATIO SPREADABILI TY RATIO

FI GURE 1.9

RELATIVE SENSITIVITY OF PARAMETERS OF SUBBASE LAYER(Tam 1 1985)

REFERENCESTRUCTURE .1 .

Ewc=4000MPa, u=0,4 hwc=40mm

Eee =IOOOOMPa, u=O,4 hec=15Omm

hRe=200mm

hse=200mm

o0,6 0,8 1,0 1,2 1,4 1,6

MAX. DEFLECTION RATIO

+

\' + -

\• Eee

~ hRe }LEA: MI X

c ER8 ASPHALT

+ E SG

1,0 1,2

SPREADA81L1TY RATIO

FIGURE 1.10

RELATIVE SENSITIVITY OF PARAMETERS OF LEAN MIX AND ASPHALT BASE LAYER (Tam ,1985)


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The mai n conc l us i on her e was t ha t def l ec t i ons ar e s ens i t i ve t o

t he var i at i on of t hi ckness of t he l ean concr et e subbase and t he

asphal t base. Hence, i t i s i mpor t ant t o know what t hei r act ual

t hi ckness es ar e t o enabl e one t o eval uat e t he condi t i on of t he

exi s t i ng pavement s wi t h conf i dence.

Pavement def l ect i on devi ces made t hei r appear ance i n 1938 i n

Cal i f or ni a. The Cal i f or ni a Di vi si on of Hi ghways i nst al l ed t he

Ge ne r a l El e ct r i c Tr a ve l Ga uge st a t e - wi de i n t h at y ea r . Thi s

t y pe o f dev i c e dev el o ped ev ol ut i o nar i l y . T hi s pr o ce s s wasenhanc ed by t he us e of t hes e dev i c es at t es t t r ac ks s uc h as

t hose at Br i ght on and St ockt on, and at WASHO and AASHO r oad

t e st s . ( Whi t comb, 198 2) . Si nce t he n t h e use of non- de st r uc-

t i ve def l ect i on measur i ng devi ces has become st andar d pr act i ce

wor l d wi de.

a ) i ncr e ase t he t e st i ng pr oduct i on r a t e

b) i ncr ease t he accur acy of measur ement s

c) si mul at e movi ng t r af f i c l oads i n t er ms of

magni t ude of l oad, shape and equi val ent t i me of l oadi ng

d) pr o vi de s i mpl i c i t y o f o per at i o n and i nt er pr et at i o n o f

r esul t s

e) r educ e t he c o s t of t es t i ng.

Most def l ect i on t est i ng equi pment can be cl ass i f i ed by l oadi ng

mode . Ge ne r a l l y t he se de vi ce s f a l l i nt o t h r e e ma i n gr oups:

st a t i c or s l ow- movi ng whe el de vi ce s, st e ady st a t e v i b r a t or y

devi ces and i mpul se or f a l l i ng wei ght devi ces. Tabl e 1. 2 l i st s

a br i e f su mma r y of t he de vi ce s a s c l a ssi f i e d by Moni smi t h

(1979) .


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Wh i t c o mb ( 1 98 2) me nt i o n s s e v e r a l o t h er s o p h i s t i c a t e d d ev i c e s .

T he mo v i ng v eh i c l e de v i c e a nd ac c e l e r o met e r s whi c h ne e d i ns t r u -

me n t i n s t a l l a t i o n i n t h e p a v e me n t , c a n n o t s t r i c t l y b e r e ga r d e d

a s n o n - d e s t r u c t i v e d e f l e c t i o n b a s i n t e s t i n g. Ot h e r s me n t i o n e d

a r e a de f l e c t i o n b ea m me as u r i ng pe r pe ndi c ul a r t o a p as s i n g

v e h i c l e , l a s e r t e c h n o l o g y a n d n e w t e c h n i q ue s i n p h o t o g r a mme t r y .

The r o ad s ur f ac e de f l e c t o me t e r ( RSD) and mul t i - d ept h de f l e c t o -

me t e r ( MDD) d e ve l o p ed i n S o ut h Af r i c a f o r u s e wi t h t h e He a v y

Ve hi c l e S i mu l a t o r ( HVS ) d es c r i b ed b y F r e e me e t a l . ( 1 98 1) c a n

a l s o b e s e e n a s r e c e nt d e ve l o p me nt s . S t r i c t l y s p e a ki n g t h e MDD

i s a d es t r u c t i v e d ef l e c t i o n me a s ur i n g d ev i c e i n t e r ms o f i t s

i nst a l l at i on pr oc edur e .


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Met hod bywh i c h l oad

i s ap p l i e d

Or gani zat i on bywh i c h u se d

( Exampl e s )

Sl ow- movi ngWhe el

Ro a d s u r f a c edef l e c t omet er(RSD)

T r a v e l l i ngdef l ec t ogr aph

Vi br at or yl oad

Li ghtv i br a t o r s , e . g .R oa d r a t e r s a n dDynaf l ec t

Fal l i ngwei gh t

Fal l i ng wei ghtdef l e c t omet er( F WD)

Asp h a l t I n s t i t u t e , Co l l e gePar k, Mar y l andNI TRR. CSI R , S ou t h A f r i c a

Cal i f or n i a Depar t ment of T r a ns por t a t i on

Tr a ns por t a nd Ro ad Re s ear c h

Lab or a t or y . Gr e at B r i t a i n.Na t i o n a l I n s t i t u t e f o r T r a n s -p o r t a n d Ro a d Re s e a r c h . S . A.Mai n Roads Depar t ment , NewSout h Wal es, Aust r a l i a,L C P C. F r a n c eL C P C, F r a n c e .

S t a t e s : Ca l i f o r n i a ,K en t u c k y , L o u i s i a n a , Ut a h .Fe der al Hi ghway Admi ni s t r a-t i on

U. S . Ar my Cor p s o f E n gi n e e r s ,Wat er ways Exper i ment St at i on

Wh i t c omb ( 1982) s t a t e s t h at c r i t e r i a f o r d e t e r mi n i n g t h e " b e st "d ef l e c t i o n t e s t i ng de vi c e f r o m a t e c hni c a l s t a ndpo i nt a r e

d i f f i c u l t t o d es c r i b e. Va r i o us c o mp ar a t i v e s t u di e s h av e b ee n

ma de . I n h i s c o mpr e he ns i v e s t udy Bus h ( 1 980) c o mpa r e d t he

o p er a t i o na l c h a r a c t e r i s t i c s ( f o r e x amp l e e a s e , s p e ed a nd ma n -

p owe r r e qu i r e me nt s ) , c o s t s ( i n i t i a l a nd o pe r a t i n g) , a c c u r a c y ,

r e pr o duc a bi l i t y o f me as u r e me nt s a nd de pt h o f i nf l u enc e o f


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Re l at i v e v al ues of 1 t o 10 we r e us e d wi t h 1 bei ng t he mos t

des i r abl e and 10 t he l eas t . The r es ul t s of t hi s t abl e c l ea r l y

i ndi cat e a pref erence f or t he Dynaf l ect Model 2008, Road Rat ers

and FWD.

The mos t compr ehe ns i ve r ec ent s t udy compar i ng non- de s t r uc t i ve

t est i ng ( NDT) devi ces and met hods f or use i n t he over l ay desi gn

of f l exi bl e pavement s i s t hat by t he Feder al Hi ghway Admi ni st r a-

t i on ( FHWA, 1984) . User comment s on t he var i ous devi ces were

c ol l e ct e d f r o m a l l o ve r t he wo r l d. T he f o l l o wi ng f a ct o r s we r e

consi der ed:

( a ) t i me i n s e r v i c e( b) c r ew si z e

( c ) pr o f e s s i o na l qua l i f i c at i o ns o f c r e w( d) numbe r o f t e s t po i nt s pe r da y( e) c os t per t es t poi nt( f ) mai nt enance cost s( g) t r a f f i c c ont r ol c os t s( h) dat a r ecordi ng met hods( i ) da t a s t o r a ge(j) t owi ng vehi cl e.

v ar i a t i o n i s a ppar e nt l y due t o a di f f e r e nc e i n us e r r a t he r t ha n

equi pment . I t does , however , gi ve a good gui de. I t i s

obvi ous t hat t he devi ce t hat comes out best wi l l depend on whi ch

f act or i s sel ect ed.

Anot her compar at i ve st udy, al so f r om t he FHWA ( 1984) st udy, i s

s hown i n T abl e 1. 5. I t c ov er s a wi de r ange of c r i t er i a and t he

f i nal r es ul t i ndi c at es t hat t he F WD i s f avour ed. The Road

Rat ers and even t he Dynaf l ect are not f ar behi nd i n t hi s r at i ng.

Thi s emphas i z es t he f act t hat eac h dev i ce has i t s s t r ong and

weak poi nt s.

A f ew r el evant concl usi ons f r om t hi s st udy by t he FHWA ( 1984)

are as f ol l ows:

( a) The Dynaf l ect , Road Rat er s and FWD ar e eqUi pped t o measur e

def l ect i on basi n par amet ers mor e qui ckl y and ef f i c i ent l y

t han t he st at i c and aut omat ed beam devi ces;


31/312

Benke l man Dynaf l ect F WD Model 400 Model 510 Model 2008beam r oad r at er r oad r a t er r oad r a t er

Opt i ona l char act er i s t i cs 6 1 5 3 4 2Ea s e 6 1 5 3 4 2Speed 6 1 5 2 2 2Manpower 6 1 3 3 3 1

SUBTOTAL 18 3 13 8 9 5N

Cost s 6 1 5 2 2 4 w

Accur acy 3 2 1 3 3 2Def l ec t i on 6 2 1 2 2 5For ce 1 4 3 5 5 1

SUBTOTAL 7 6 4 7 7 6

Tr an s po r t a bi l i t y byc ar go ai r c r a f t 1 2 2 3 2 2

Dept h of i nf l uenc e 1 5 2 6 4 3

Sui t abi l i t y 6 3 1 5 3 1

TOT AL S 23 14 16 22 18 14


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TABLE 1.5:COMBINED RATINGS REPORTED IN

LITERATURE (LARGER NUMBERS

INDICATE BETTER RATING)

Rating Criteria Dynaflect RR 400B RR2000 FWD

Costper lane mile 9.5 10.0 9.2 7.5

Operator training 10.0 10.0 10.0 10.0

Speed of operation(1) 7.5 10.0 10.0 10.0

Traffic Interference (1) 7.5 10.0 10.0 10.0

Ease of data collection(2) 10.0 10.0 10.0 10.0

Ease of calibration (3) 2.0 5.0 5.0 10.0

Equipment versatility(4) 0 10.0 10.0 10.0

Actual load capability(5) 1.0 2.9 5.5 10.0

Design compatibility 10.0 10.0 10.0 10.0- -- - -Combined rating 57.5 77.9 79.7 87.5

( I) Based on the theoretica I test program.

(2) Assumes the recommended options.(3) Based on the time required for calibration.

(4) Based on ability to vary the applied load.

(5) Based on ability to produce a 10,000 lb. dual wheel load.


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( b) The aut omat ed beam devi ce, FWD and Road Rat er model 2008

can devel op l oads at , or near, nor mal desi gn l oads;

( c ) L oad as wel l as def l ec t i on c an eas i l y be meas ur ed. The

Road Rat er s and FWD ar e equi pped t o measur e l oad as wel l as

def l ect i on;

( d) De vi ces capabl e of pr oduci ng se ve ra l l oad l ev el s up t o, or

near , des i gn l oads c an be us ed t o det er mi ne t he s t r es s

sensi t i vi t y of pavement sys t ems, and

( e) St eady st at e dynami c devi ces, whi ch use a r el at i vel y heavy

st at i c pr e- l oad, change t he st r ess st at e i n t he pavement

bef or e t he t est i ng.

The s l ow- movi ng wheel dev i ces l i ke t he Benkel man beam and

def l ect ogr aphs may be seen as r epr esent i ng t he f i r st generat i on

of measur i ng deVi ces; t he vi brat ory and f a l l i ng wei ght devi cesar e mo r e r ec ent dev el opment s . Of pr i me c onc er n i s t he f ac t

t hat t he sl ow- movi ng devi ces are nor mal l y associ at ed wi t h a

si ngl e measur i ng poi nt , wher eas t he l at er gener at i on measur i ng

devi ces are i ncr easi ngl y abl e t o descr i be t he def l ect i on basi n.

Thi s i s nor mal l y ac hi eved wi t h t he equal l y s pac ed meas ur i ng

poi nt s away f r om t he poi nt of l oadi ng. The devel opment of t he

RSD ( F r ee me et a 1. 1981) and modi f i cat i on of t he st a ndar d

Benkel man beam and Lacr oi x def l ect ogr aph ( Ander son, 1977) , whi ch

can pr oduce a " cont i nuous" pl ot of t he def l ect i on basi n, over -

come t hi s di sa dv ant age . I n gener al i t can be st at ed t hat t he

mor e accur at e t he measur i ng devi ce can measur e t he def l ect i on

ba si n, t he bet t er i t i s .


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The curviameter can strictly be called a fast rolling wheel

technique. The Technical Committee Report on flexible roads of

the XVII World Road Congress (Permanent International

Association of Road Congresses, 1983) described it as follows;

"The Curviameter carries a velocity-sensitive transducer on an

endless moving chain that places and replaces the transducer in

advance of the loaded dual wheels of a lorry moving at 20'km/h.

Although the machine gives an increase in route-capacity of

rolling wheel techniques the derived deflections and curvatures

are of limited accuracy."

The slow-moving wheel devices generally measure deflection with

a standard axle load. Depending on the measuring technique of

the wheel moving to or from the measuring point, deflections can

vary. Although a lot can be said for these techniques and

devices simulating the actual moving wheel loads (more accu-

rately), it must be remembered that the simulation is normally

much slower than the real situation and effects like plastic

deformation come into play. In this regard Whitcomb (1982)

states that the input from the static and vibratory devices

commonly used bears little resemblance to the input from an

actual vehicle. Molenaar and Koole (1982) mention that the low

force levels of the light vibrators on predicted pavement

behaviour are a cause for concern. This concern is not only

with respect to possible non-linear behaviour of the pavement,

but also with respect to errors in measurement, particularly

measurements taken at the extremes of the deflection basin where

deflections measured and normal variations of instruments are of

the same magnitude. The heavy vibrators described by the

Federal Aviation Administration (1979) have adequate loading

force, but are mainly used to evaluate airfield pavements.

The FWDmeets all requirements for reliability, reproduction,

accuracy, simulation of moving wheel loads and measuring the

whole deflection basin and it does not alter the conditions of

the pavement before loading (Whitcomb, 1982). The FWDcan vary

the force from 40 to 125 kN and will represent any loading


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I. 28

condition on a pavement or airfield realistically (Claessen and

Ditmarsch, 1977 and Koole, 1979). Ullidtz (1982) concludes that

the FWDsimulated the influence of a heavy fast-moving wheel load

on the maximumvalues of the deflections, stresses and strains in

the pavement structure.

In the study by the University of Dundee (1980) it is shown that

when equipment measuring deflection with dual wheel loads is

used, (for example the Benkelman beam), the maximumdeflection

is not located at the centroid of the loading area. This is

illustrated by the results of a typical analysis in Figure 1.11.

Anderson (1977) also recognizes the importance of this pheno-

menon and noted that it might lead to wrong conclusions,

particularly for relatively weak (thin) pavements. He sug-

gested that field performance should be calibrated with analysed pavements before being adopted in the design phase. The former

study recommended the use of a single wheel device and proved

that deflections measured at the extremes of the loaded area did

not significantly vary from deflections measured inside the

loaded area. Dehlen (1962b) also recognized this phenom~non of

d (maximum) and R minimumbeing situated under the loaded area.o

The transverse position also lead to the more severe curvature

parameters measured of the deflection basin. This is illus-

trated in Figure 1.12. Dehlen (1962b) statesj "The longitudinal

elongation observed in many chicken net crack patterns is, as

has been pointed out by others, another indication that the

factors giving rise to cracking are most severe in the trans-

verse direction."

The Technical Committee Report of the XVII World Road Congress

(Permanent International Association of Road Congresses, 1983)

states that interest in developing analytical design methods is

linked more to stationary test techniques than to the rolling

wheel techniques. The light vibrators are obviously ideal for

standard field work as Tables 1.3, 1.4 and 1.5 indicate. In spite

of the advantages of using the FWDmentioned earlier, Molenaar

and Koole (1982) comment that, according to conclusions of a

study group of the Dutch Study Centre for Road Construction, the


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0,4

x( m)

x jm)

~~STRUCTURE 3.4 .".,." , /"A. __ M

~ 4;'/ _~- J.

--- "r/ ~ .--.--.- - - ....•...--7.~ - - - - ..~ ., . . " " " . - -

___________ 0,29 z (mm) _

( m)

0,0 -

0,05 _.-0,1

---0,15 ---

om

l

o)•V

IV

I

o--

WHEEL LOAD

AREA -

- - - --- - ....r'---LOCUS OF MAXfY DEFLECTIONFIGURE 1.11

TRANSVERSE DEFLECTION PROFILES(University of Dundee 11980)


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INCHES

30 20 20 30

-U)WJ:(,)

,020z-- -z SITE A 1 ROUTE 3/ I .w0 0- ~u ~b ~ul- DEFLECTION(,)

,040 ,03011

,02611

;03211

W...J

Rtu Rtb RtuLL RADII

w CURVATURE 1551

- 901

1251

0

,060

FIGURE 1.12

TYPICAL EXAMPLE OF TRANSVERSE DEFLECTION

PATTERN BENEATH DUAL WHEELS (Dehlen, 1962 b)


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I. 31

Lacr oi x def l ect ogr aph i s mor e sui t abl e f or r out i ne eval uat i ons

t han t he FWD. The RSD devel oped i n Sout h Af r i ca over comes t he

nor mal pr obl ems exper i enced wi t h a st andar d Benkel man beam

c onc er ni ng po or s a mpl i ng f r equenc y and t es t i ng i n adv er s e

we at he r cond i t i ons. Owi ng t o t h e l i mi t e d l e ngt h of a ny su ch

beam devi ce t he pr obl em of t he beam s uppor t s bei ng i nsi de t he

de f l e ct i on ba si n wi l l not be e l i mi na t e d compl e t e l y . Thi s i s

par t i cul ar l y t r ue of st i f f er pavement s wher e t he def l ect i on basi n

i s br oad. The Techni cal Commi t t ee Repor t on f l exi bl e Roads of

t he XVI I Wor l d Road Congr ess ( Per manent I nt er nat i onal Ass oci at i on

o f Ro ad Co ngr e s s es , 1983) a l s o c onc l udes t hat ; " P r ec i s i o n o f

me asu r e me nt ca n be di f f i cul t whe n t e st i ng st i f f pa ve me nt s

cont a i ni ng ce me nt e d l a ye r s a nd cr a cki ng i n t hose l a ye r s ca n

r educe t he si gni f i cance of measur ement s of t he def l ect ed shape. "

Ther e ar e numer ous r ef er enc es i n t he l i t er at ur e t o t he cor r e-

l a t i on of de f l e ct i ons obt a i ne d wi t h t he di f f e r e nt de vi ce s.

Gener al l y t he newer gener at i on measur i ng devi ces ar e cor r el at ed

wi t h t he ol de r g ene r a t i on de vi ce s l i ke t he Be nkel ma n be am.

Whi t comb ( 1982) r ecor ds r el at i onshi ps bet ween t he Road r at er .

Dynaf l ect and Benkel man beam or t r avel l i ng def l ect omet er .

Hoyi nck, et a l e ( 1982) even cor r el at e Lacr oi x def l ect ogr aph and

Benkel man beam def l ect i ons measur ed wi t h di f f er ent t echni ques.

The r eas on f o r t he cor r el at i ons i s t hat one t ype of def l ec t i on

measur ement may be t r ansl at ed i nt o anot her , s o t hat empi r i cal

or est abl i shed i nt er pr et at i on gr aphs can be used wi t hout t he

measur ement havi ng t o be r epeat ed i n t he pr escr i bed manner .

I n addi t i on t o t he r eason not ed above, Whi t comb ( 1982) not es

t hat t he newer gener at i on vi br at i ng measur i ng devi ces of f er

s i gni f i ca nt a dv ant a ge s of e ase a nd sp ee d of ope r a t i on ove r t he

Benkel man beam and Cal i f or ni a def l ect omet er .

Moor e et al e ( 1978) make t he f ol l owi ng st at emen~ on t he qual i t y

of su ch cor r e l a t i ons: " Al l of t he st e ady st a t e dy na mi c d ef l e c-

t i on devi ces can be expect ed t o cor r e l at e r easonabl y wel l wi t h


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s t a t i c de f l e ct i o n me as ur e me nt s . Ma ny e va l ua t i o n pr o ce dur e s

empl oy t hese dynami c def l ect i on devi ces f or est i mat i ng t he

ant i ci pat ed usef ul l i f e ( or l oad- car r yi ng capaci t y) of pavement s

based upon corr el at i on of t he measur ement s wi t h st at i c def l ec-

t i on measur ement s " .

I t i s o bv i o us t ho ugh, f r o m t he di s c us s i on o n de f l e ct i o n pa r a -

met ers ( see 1. 3. 2) t hat t he corr el at i on of a s i ngl e def l ect i on

poi nt , l i ke a Benkel man beam def l ect i on, wi t h a hi ghl y compl i ca

- t ed def l ect i on basi n descr i pt i on wi l l not necessari l y be a good

one. For t hi s r eason Whi t comb ( 1982) caut i ons about t he use of

appl yi ng publ i shed cor r el at i ons wi t hout some knowl edge of t he

de gr e e t o whi c h t he t wo v ar i a bl e s ha ve be en c or r e l a t e d. I t i s

more desi rabl e t o avoi d t he need t o make t he corr el at i ons at al l .

The f ol l owi ng i s quot ed f r om t he FHWA s t udy ( 1984) : On t he

c or r el at i ons bet ween NDT def l ec t i on devi c es " I n gener al , a

di f f e r e nt c or r e l a t i o n s houl d be de vel o pe d f o r e ac h ma j o r pa ve -

ment t ype and f or di f f erent pavement t hi cknesses wi t hi n par t i -

c ul a r t y pe s o f pa ve me nt be ca us e t he c or r e l a t i o n i s no t uni que ,

. . •. " . Regardi ng t he i nt erchangeabi l i t y of dat a t he f ol l owi ng

i s al s o quot ed: " T he s our c e, t es t i ng pr oc edur e and equi pment

conf i gur at i on used i n devel opi ng t he dat a must be f ul l y under -st ood bef or e dat a col l ect ed by anot her agency can be used. "

( a) r eal i s t i c al l y s i mul at e mov i ng t r af f i c l oads i n t er ms of

magni t ude of l oad, shape and equi val ent t i me of l oadi ng

( b) ac c ur at el y meas ur e t he whol e def l ec t i on bas i n wi t h hi gh

l evel s of r epr oduci bi l i t y

( c ) be s i mpl e t o oper at e, s o t hat i t i s pos s i bl e t o us e i t wi t h

c ompe t e nc e i n t he f i e l d; but i t s houl d a l s o be a ppl i c abl e t o

r e s e a r c h


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I. 33

( d) be capa bl e of a t t a i ni ng hi gh l ev el s of pr oduct i v i t y , whi ch

must r educe t he cost of t est i ng.

Consi der i ng t hese pr er equi si t es, i t seems t hat t he FWD i s t he most

appr o pr i at e o f t he dev i c es di s c us s e d. As f ar as c os t and eas e o f

oper at i on i n par t i cul ar ar e concer ned, t he vi br at or y devi ces such

a s Dy naf 1e ct a nd Road Rat e r s a r e a l so consi de r e d a ppr opr i a t e .

The mai n adv ant age of t hes e newer gener at i on def l ec t i on meas ur i ng

devi ces l i es i n t he f act t hat t hey nor mal l y measur e at l east f our

poi nt s on t he def l e ct i on ba si n. The modi f i e d RSD or Be nkel ma n

beam and a moder ni zed Lacr oi x def 1ect ogr aph ar e abl e t o moni t or

t he def l ect i on basi n at f r equent i nt er val s i n spi t e of t her e bei ng

onl y one mea sur i ng poi nt . The La cr o i x de f 1e ct ogr a ph i s use d by

t he r oad a ut hor i t i es i n Sout h Af r i ca on a ne t wor k ba si s wi t h a

pr ov en l ev el of ef f i c i enc y. A vas t amount of i nf or mat i on i savai l abl e on var i ous pavement st r uct ur es f r om HVS t est i ng and on

f ul l st r uct ur al 1i ves measur ed wi t h t he RSD and MDD on t he same

l ocat i on. The i nf or mat i on gai ned f r om t hese devi ces may be used

t o det er mi ne sui t abl e def l ect i on basi n par amet er s accur at el y or t o

per f or m r eal i st i c cor r el at i on st udi es bet ween t hese par amet er s.

I t i s poss i bl e t o use def l ect i on basi n measur ement s obt ai ned f r om

a moder ni zed Lacr oi x def 1ect ogr aph f or mor e det ai l ed anal ysi s.

To dat e onl y t he max i mum def l ec t i on U s ) has been us ed t o di s -o

t i ngui sh bet ween var i ous uni f or m sect i ons of r oad st at i st i cal l y.

By t he use of def l e ct i on ba si n pa z: a me t e r s r e l a t e d t o sp eci f i c

pavement st r uct ur e t ype and st at e a hi gher l evel of engi neer i ng

i nt er pr et at i o n and ef f ec t i v e s e r v i c e c an be pr o vi ded f o r t he

pur pose of pavement management , r ehabi l i t at i on and over l ay desi gn.

I t i s s ugges t ed t hough, t hat t es t s be done wi t h t he F WD and

vi br at or y def l ect i on basi n measur i ng devi ces i n Sout h Af r i ca i n

v i e w of t he i r adv ant age s ment i one d a bove. The se de vi ces wi l l

hav e t o be cor r el a t e d wi t h t he a bove - me nt i one d da t a bank ondef l ect i on measur ement s f r om HVS si t es i n or der t o ensur e uni f or m

st andar ds of def l ect i on i nt er pr et at i on.

The par a met e r s of t he def l ec t i on bas i n mus t -

( a) r e) pr esent t he f ul l char act er i st i cs of t he whol e def l ect i on

basi n ( not onl y maxi mum def l ect i on ( 0 ) , but r at her a combi -o


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I. 34

nation of parameters like SCI and BCI covering the whole

deflection basin);

(c) be able to relate to the structural characteristics of the full

depth of pavement structures.

From the survey it is obvious that in the past at least two

deflection points on the deflection basin are normally needed in

an analytical procedure. One such point is the point of maximum

deflection (0). The other point should preferably be varied ino

distance relative to the centroid of the loaded area (0) inr

accordance with prescribed requirements. Examples of such

parameters are Q and ST, which still require other points measured

on the deflection basin in order to select a value of O.r

Another alternative is to use fixed values of radius for de-

flection points, for example 00' 03

05' 0610' etc. It is sug-

gested that the parameters that use these deflection values, for

example SCI, ST, BDI, BCI, etc., be investigated in view of the

guidelines described above and the equipment available in South

Africa. A further suggestion, which will be discussed in more

detail in· a later section, is that these selected parameters be

related to the pavement structure classification used in TRH4

(NITRR, 1985a) and to pavement performance models. A parameter

like SCI will then be determined differently for a granular base

than, for example, from for a cemented base pavement, reflecting

its different deflection basin characteristics and structural per-

formance.


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MEASUREMENT AND DATA PROSESSI NG OF

DEFL ECTI ON BASI NS I N SOUTH AFRI CA


44/312

2.2

2. 2

2. 1 Measur i ng equi pment2. 2 The pr oc edur e

2. 22. 3

2. 2. 1 Si t e sel ect i on and pr eparat i on2. 2. 2 Measur i ng pr ocedure

2. 32. 6

3. 1 P r e - aut omat i on dat a ev al uat i on ( Rebound pr oc edur e) 2. 93. 2 Aut omat ed dat a eval uat i on ( WASHO pr ocedur e) 2.14

4. THE NEED FOR CURVE FI TTI NG PROCEDURES 2. 1 7

5. PROPOSED DEFL ECTI ON BASI N MEASURI NG EVALUATI ON PROCEDURE 2.19

5. 1 Dat a mani pul at i on and pr epar at i on 2.195. 2 Hi gher l evel def l ec t i on bas i n dat a mani pul at i on 2. 20

6. CONCLUSI ONS AND RECOMMENDATI ONS 2. 25


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I n S o ut h A f r i c a t h e u s e o f t h e f u l l d ef l e c t i o n b as i n wa s g en er a l l y

n eg l e c t e d i n t h e a na l y s i s o f d ef l e c t i o n ba s i n p ar a me t e r s . I n t he

p as t t h e a na l y s e s we r e mo s t l y c o n c en t r a t e d o n t h e s ma l l a r e a o f t h e

d ef l e c t i o n b as i n i n t h e v i c i n i t y o f ma x i mum d ef l e c t i o n. I n t he

p r o gr a m o f a c c e l e r a t e d t e s t i n g wi t h t h e He a vy Ve hi c l e S i mu l a t o r

( HVS) f l e e t i n Sout h A f r i ca . t he whol e def l e c t i on bas i n i s me asur e d

o n t h e s u r f a c e a nd i n d ep t h o f t h e p av e me nt s . T h e s a me l i mi t a t i o nof dat a anal ys i s was c onc ent r at ed on t he s mal l ar ea of t he

d ef l e c t i o n b as i n n ea r t h e v i c i n i t y o f t h e ma x i mu m d ef l e c t i o n f o r

t h es e d ep t h d ef l e c t i o n b as i n s me as u r e d. I n t h i s c h ap t e r a br i e f

de scr i p t i on i s g i ve n of how t he sur f ace de f l e c t i on bas i n i s me asur e d

i n S o ut h A f r i c a b y me a ns o f t h e a ut o ma t e d B en k el ma n b ea m o r a l s o

c a l l e d t h e r o ad s u r f a c e de f l e c t o me t e r ( R S D) . T h e p r o c ed ur e a nd

e qu i p me nt t o me a s ur e t h e d ef l e c t i o n b as i n a t v a r i o us l e v el s i n t h e

de pt h of a paveme nt by me ans of a mul t i - de pt h de f l e c t ome t e r ( MDD)

ar e a l so br i e f l y d i sc usse d .

T he pr es ent da t a ana l ys i s pr oc ed ur e i s di s c us s ed. Bas ed on t h i s and

a d i s c u s s i o n o f t h e wh ol e d ef l e c t i o n b as i n a nd r e l a t e d p ar a me t e r s .

t he a ut ho r s ugges t s c ha nges t o t hi s da t a a na l y s i s pr o cedur e.

S p ec i f i c r e f e r e nc e i s ma de o f t h e n ee d f o r a b et t e r d es c r i p t i o n o f

t h e f u l l d ef l e c t i o n b as i n • C ur v e f i t t i n g mo de l s a r e d i s c u s s e d

br i e f l y and r ecommendat i ons ar e made f or pr act i cal use wi t h t he r oad

sur f ace def l ect omet er ( RSD) and t he def l ect ogr aph •.

HVS t e s t i n g i s d on e b y r e pe a t e d a pp l i c a t i o n o f a c h os e n wh ee l l o a d

t o t he r oad s t r uc t u r e . Se ve r a l soph i s t i cat e d i ns t r ume nt s ar e use d


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t o moni t or t he r es pons e of t he r oad. I n t he f i el d. a mi c r o - pr o-

c es s or s y s t e m i s us ed t o r ec or d t he meas ur ed dat a on a magnet i c

di s c . The dat a on t he magnet i c di s c i s t hen t r ans por t ed t o t he

cent r al l abor at or y i n P r e t o r i a f or pr oces s i ng by t he mai n compu-

t ers ( Fr eeme. et al . • 1981) . Dur i ng an HVS t est t he measur ement sof t he s ur f ac e def l ec t i on and c ur v at ur e of t he pavement wi t h an

aut omat ed Benk el man Beam. al s o c al l ed t he Road Sur f ac e

Def l ec t omet er ( RSD) ( Bas s on. 1985) . ar e c ol l ec t ed as dat a.

El ast i c def l ecti on and permanent def ormat i on measurement s ar e

t ak en at di f f er ent dept hs wi t hi n t he pavement us i ng t he mul t i -

dept h def l ect omet er ( MOD) . ( Basson. et al . 1980. )

The MOD i s a devi ce t hat can s i mul t aneous l y meas ur e t he ver t i cal

def l ect i ons and per manent def or mat i ons of up t o s i x poi nt s on a

ver t i c al l i ne i n any pav ement . The met hods of s i t e pr epar at i on

and i l l ust r at i on of t he MOD i s shown i n Fi gur e 2. 1. The RSD i s an

el ectr oni cal l y i nst r ument ed def l ect i on beam whi ch can measure

dynami c r es i l i ent def or mat i ons t o an accur acy of ± 0. 01 mm.

( Shackel . 1980. ) Thi s modi f i ed Benkel man Beam ( t he RSD) and t he

us e of t he RSD and MOD pl us ot her r e l at e d i ns t r ument s ar e

i l l us t r at ed i n Fi gur e 2. 2. The modul es of t he MOD and t he

meas ur i ng poi nt of - t he RSD mak e us e of a l i near var i abl edi f f er ent i al t r ansf or mer ( LVDT) t o measur e pavement def l ect i ons.

Thi s di s cus s i on s er ves onl y as a br i ef des cr i pt i on of t he

equi pment used t o measure def l ecti ons i n dept h and on t he surf ace

of a pavement st r uct ur e bei ng t est ed wi t h t he HVS.

A t y pi c al HVS t es t s ec t i on i s s el ec t e d af t er a def l ec t o gr a ph

s ur vey of t he r oad l engt h was done. Uni f or m s ec t i ons of t he

r oad ar e t hen i dent i f i ed whi c h di f f er s i gni f i c ant l y s t at i s -

t i c al l y . A dec i s i on i s made whet her t o s el ec t a s ec t i on t hat

r epr es ent s f or exampl e t he 85t h per cent i l e. 15t h per cent i l e or

aver age of t he r oad i n t er ms of t he def l ec t o gr aph s ur vey . A

det ai l s ur vey of each met er of nor mal l y a 100 met er s e ct i on i s


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SURFACE COVER

SURFACE CAP

FIGURE 2.1

METHODS OF SITEPREPARATION OF THEMULTI-DEPTH - DEFL ECTOMETER

SURFACE COVER

SEALSOCKET CONNECTOR

SURFACE CAP

MOO MODULE

L V OT C O R E

RUBBER. LINING

RUBBER SLEEVING

INTER CONNECTING ROO


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WHEEL SPEED/POSITION

WHEEL LOAD

HVS.TEST

WHEEL

PERMANENT AND ELASTIC DEFLECTION

TEMPERATURE GRADIENT

~----- •. SOIL SUCTION PROFILE

CELASTIC DEFLECTION

LVDT

MULTI- DEPTHDEFLECTOMETER

FIGURE 2.2

THE HVS SECTION INSTRUMENTATION


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t hen car r i ed out wi t h t he s t andar d Benk el man Beam. Bas ed on

t hes e r es ul t s a 8 met er s ec t i on of r o ad i s s el ec t ed whi c h i s

uni f or m i n t er ms of i t s maxi mum def l ect i on measur ement s.

Ot her f act or s s uch a s r oad s af et y, gr adi ent et c. ar e al s o

c ons i der e d i n t he s el ec t i on of s uc h an HVS t es t s ec t i on.

( Shackel , 1980. ) I n s ome cases, part i cul ar l y shor t

ex per i ment al s ec t i ons , t he s el ec t i on of a s i t e may f ol l ow a

di f f er ent pr ocedur e, but t he ai m i s normal l y t o have at l east an

HVS t es t s ec t i on t hat i s uni f or m over i t s 8 met er l engt h i n

t er ms of Benkel man Beam def l ect i ons.

The i ns t r ument at i on and mar ki ng of s uch a s el ect ed t es t s ect i on

i s as s hown i n F i gur e 2. 3. As c an be s een, nor mal l y at l eas t

t wo MOD hol es are i nst al l ed whi l e t he RSD measur i ng poi nts are

mar k ed on t he s ur f ac e i n or der t o r epr es ent t he whol e s ec t i on

and enhance r epeat abi l i t y.

The dual wheel wi t h t he s peci f i ed t yr e pr es s ur e and l oad i s

mov ed ± 3 meter s away f r om t he measur i ng poi nt. The def l ect i on

pr oduced by t he l oad appr oachi ng t he measuri ng poi nt of ei t her

t he RSD or MOD i s r ec or ded on a c har t as a c ont i nuous t r ac e,

whi l e swi t ches, at measur ed di st ances al ong t he r oad, r ecor d t he

pas s age of t he l oad pas s i ng t hem. A t y pi c al t r ac e i s s hown i n

Fi gur e 2. 4. The s quar e waves of t he s wi t c hes r e f l ec t t he

var i anc e i n s peed at whi c h t he wheel l oad appr o ac hes t he

meas ur i ng poi nt i n or der t o f ac i l i t at e t he c or r ec t i on t o r el at e

di st ance t o def l ect i on accur atel y. The l oaded wheel moves past

t he measur i ng poi nt f or a di st ance of about 1, 2 met er wher eaf t erpul ses si mul ati ng measur ement s are generat ed aut omat i cal l y t o

compl ete t he st andar d set of 256 measur ement s of a def l ect i on

bas i n. Each meas ur ed poi nt on t hi s s et i s a s t andar d di s t ance

apar t , us ual l y 22, 07 mm, dependi ng on t he s wi t c h c har ac -

t eri st i cs. Usual l y measur ement sets wi t h t he MOD are t aken onl y

on t he cent r e l i ne and wi t h t he RSD i n l i ne wi t h t he measur ement

poi nt . Of f - cent r e measurement s can be t aken wi t h t he MOD. At


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M = MUL T1- DEPTH OEFLECTOME~TER

o = ROAD SURFACE OEFLECTOMETERP = PROFILOM£TER

C = HOLE FOR NUCLEAR MOISTURE METER

PRETOR1A~ --.. KRUGERSOORP

TEST SECTION 136A4 WATER HOLES

CROSSFALL 200mm FROM SECTION EDGE EACH O,6m DEEP

; 1~ N

~ ~ .5 m ~ 1

8m

~ I .. . . . ,

200 mm

t°T 0 0E £ : 0 M 0 M 0 M 1m

ol - D 0~200 mm

WATER TABLE HOLES

2 3 4 5 6 7 8 9 10 II 12 13 14 15 16

P P P P P P

FIGURE 2.3

TYPICA L LAYOUT OF TEST AND CONTROLSECTION


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FIGURE 2.4

TYPICAL RECORDED CHART FROM RSD MEASUREMENT SHOWING DEFLECTION AND SQUARE

WAVE PRODUCED


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l e a s t 2 me a s ur e me nt s e t s a r e t a k en a s c o n t r o l a t e a c h me a s ur i n g

poi n t o f t he RSD and MOD at a spe c i f f i c t i me dur i ng t he t e st i ng.

Va r i o us wh ee l l o ad a nd t y r e pr e s s u r e c o mb i n at i o ns a r e u s ed

dur i ng meas ur ement s.

I t i s i mp or t a nt t o n ot e t h at t h e me t h od o f me a s ur e me nt o f t h e

s t a nd ar d B en ke l ma n B ea m a nd t h at o f t h e R S D a nd MOD un de r HVS

cond i t i ons d i f f e r . T he RSD and MOD me asur e me nt s use t he WA SHO

pr oce dur e ( Mon i smi t h , 1979) wh i l e wi t h t he s t andar d B e nke l man

B e am t he r e bound pr oce dur e i s use d . I n t he WA SHO pr oce dur e t he

l o a d a pp r o a c he s t h e e nd o f t h e p r o be o r me a s ur i n g p oi n t a nd t h e

d ef l e c t i o n i s o bs e r v ed . I n t h e r e bo un d p r o c ed ur e t he wh ee l

moves away f r om t he measur i ng poi nt and r ebound of t he pavement

i s mea sur ed. Rebo und def l ec t i o n i s a bo ut t wo t i mes t he

d ef l e c t i o n me a s ur e d wi t h t h e WA S HO p r o c e du r e . T h i s ma y v a r y

wi t h t h e t y pe o f p av eme nt me as u r e d. T h i s i s p r o ba bl y d ue t o

pl as t i c def or mat i on.

T he Benk el man Beam was us ed ver y ef f ec t i vel y by De hl en ( 196 1) t o

me as u r e d ef l e c t i o n- d i s t a nc e c u r v e s ma nu al l y . T h i s wa s d on e b y

meas ur i ng t he def l ec t i o n ba si n ma nua l l y a t 3 i nc h ( 75 r o m)

i nt e r v a l s a s t h e wh ee l l o ad a pp r o ac he d t he me as u r i n g po i n t .

Smoot h cur ve s we r e dr awn t h r ough t he p l ot t e d poi n t s . Par t i cu l ar

c a r e wa s t a k e n o v er t h e c e nt r a l 2 f e et ( 6 10 r o m) , and any i r r egul ar

c u r v e r e j e c t e d. T h i s i s i l l u s t r a t e d i n F i g ur e 2 . 5 . T h e ma x i mu m

d ef l e c t i o n wa s o bt a i n ed d i r e c t l y f r o m t h e o bs e r v a t i o ns . T he

r a di us o f c ur v at ur e a t t he po i nt o f ma xi mum de f l e ct i o n wa s

o bt a i n ed b y d et e r mi n i n g t h e c i r c l e wh i c h i s t h e b es t f i t t o t h e

c ur v e o ve r t he c ent r a l 6 o r 9 i nc he s ( 150 t o 2 25 r o m) . The r adi us

of cur vat u r e of t he r oad sur f ace was t he n comput e d f r om t he r ad i us

of t he c i r c l e of be st f i t f r om t he f or mul a ;

vR = r . h2


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Radius of curvaturemeasured


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wher e R = r a di u s o f c u r v a t u r e o f r o a d s u r f a c e ,

r • r a di u s o f p l o t t e d c i r c l e , i n t h e s a me u ni t s a s R ,

v = v e r t i c a l s c a l e o f p l o t e x pr e s s e d a s a d i me ns i o nl e s s

r at i o,

h • h or i z o n t a l s c a l e o f p l o t e x pr e s s e d a s a d i me ns i o nl e s sr at i o

De h l e n ( 196 1) not e d t hat a c i

complete aspects of deflection basin parameters in mechanistic det , horak emile, 187 tesis doctoral...

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