MLS - APT’s Role in Pavement Design Model Development

MLS and MMLS3 Innovative APT Technology and Applications

移动式路面加速加载系列 MLS 和 MMLS3创新技术和应用

Prof Fred Hugo Prof Fred Hugo PE FSAAE DEng PhDPE FSAAE DEng PhD南非工程院院士 南非工程院院士

南非南非 -- 中国交通合作中心中国交通合作中心 SACTCCSACTCC 顾问顾问 AdvisorAdvisorBeijing 16 May 2008Beijing 16 May 2008 年年 55 月月 1616 日 北京 日 北京

APT is controlled application

of wheel loading

to pavement structures

for the purpose of simulating effects

of long-term in-service loading conditions

in a compressed time period

Definition of APT (after Hugo,2004 Synthesis 325)

路面加速加载试验的定义

What do we want to know and why?主要点

1. Deflection >>related to stress and strain

2. Rutting >>related to deformation

3. Stiffness changes >>related to response and performance

4. Distress Mechanisms and related models and transfer functions

1. Deformation >>rutting

2. Flexural performance >> fatigue and cracking

3. Shear >> deformation/cracking

4. Environmental response and performance >>

hot / cold / wet / dry

What do we want to know and why?(cont) 续

1. Loading rate>>related to stress and strain

2. Range of validity of characteristics >>related to extrapolation and prediction of of response and performance

3. Effect of Aging >>related to response and performance

4. Effect of Densification >>related to response and performance

5. Effect of Material Properties >>related to response and performance

6. Validation of analytical tools

Innovative Technological Tools for Evaluating MLS APT Response and Performance

创新技术和特点

•Varying Size of Facility 不同比例 MMLS3 - 1/3 scale 三分之一 MLS10 - full-scale 足尺 MLS66 - full-scale 足尺

•Mobile Testing Facility 移动式测 试多种工况

Innovative Technological Tools for Evaluating MLS APT Response and Performance (cont)续

•Multiple Wheel Trains•Lateral Wander•Varying Test Length•Varying Speed and Frequency•Varying Tyre Pressures•Varying Tyre Tread•Varying Load Amplitude

Two MLS66 being delivered in 2008两台超大型 MLS66 在 2008 年投入使用

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同济大学和辽宁省交科院

同济大学和辽宁省交科院

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UNIQUE MLS CHARACTERISTICS COMPARED TO OTHER LINEAR

TRAFFICKING DEVICES MLS 的加载独特特点

CHARACTERISTIC COMPARISON CONCLUSIONS/ COMMENTS

Cumulative load applications in unit

time MLS > OTHER

MLS Capital cost per load application <

MLS < dependent on

overloading for acceleration. o Beneficial for testing stress

dependent materials

UNIQUE MLS CHARACTERISTICS COMPARED TO OTHER LINEAR

TRAFFICKING DEVICES 续

CHARACTERISTIC COMPARISON CONCLUSIONS/ COMMENTS

Time per APT test based on number of

load applications

MLS greater than

or equal to

OTHERS

MLS Operational cost per

load application < o MLS > flexibility for

selecting test protocols

Testing of parallel sections in sequence possible to achieve similar environmental conditions

UNIQUE MLS CHARACTERISTICS COMPARED TO OTHER LINEAR

TRAFFICKING DEVICES 续

CHARACTERISTIC COMPARISON CONCLUSIONS/ COMMENTS

Range of frequency and speed

MLS > OTHERS

Frequency, Speed and Load influence Pore pressures and pumping o MLS > scope for

studying wet surface trafficking

Performance of visco-elastic materials differs due to load frequency o MLS > scope for

studying HMA

UNIQUE MLS CHARACTERISTICS COMPARED TO OTHER LINEAR

TRAFFICKING DEVICES 续

CHARACTERISTIC COMPARISON CONCLUSIONS/ COMMENTS

Uni-directional trafficking with lateral

wander

MLS does not use bi-

directional trafficking

to gain load

applications as some

OTHERS

Pore pressures and pumping affected o MLS simulates performance

of jointed pavements better Residual stresses in Asphalt

affected o MLS simulates performance

better

A Brief Review of Case Studies as

Introduction to the Topic 实际情况回顾 • In Mozambique ANE embarked on an APT

program by WB as most cost effective means to: – Evaluate construction techniques – Determine most economical use of available

sub-standard materials in a composite pavement structure

– Develop a mechanistic-empirical design system best suited for its needs with due regard to materials and environment

Mozambican Pavement Structure Problem Statement 世行项目

PHASE 1

Problem Statement

Guidelines for Transfer Functions

Model APT and Material Testing

Evaluation of Existing Practise

ID Critical Moz Pavement

Engineering Parameters

Research

Overview

研究总观

PHASE 2

Spec for Design and Constr of Full-scale

Test Sections

Constr of Test

SectionsAPT

Deflection Stiffness Rutting Cracking Diagnostics

Failure Mech

Stiffness Perform Func

Stiffness -Deflection Relation

Fatigue Perform Func

CTB Mat Load Equiv

Input for MMPDM

i t o

Material Charac,Related Pavem Structures and Construction

Method towardsPavement EconomicsMLS10

MMLS3APT

Protocols Interface Flexural

200μm electron microscope photos of yellow sand vs. red sand

(hydrometer results compatible)

yellow red

Scaled Subbase and Base in Laboratory试验室

Namibia Field Application LTPP comparable to MMLS3 Performance Prediction

Field testing in Namibia

Rut after wet field testing

Latest Laboratory Test Bed,

Profilometerand

Water Heater

MLS studies MLS studies in global perspective 2008in global perspective 2008

Applications MMLS

MMLS3 Labs

USEurope

Africa

MLS10/66 Owners/ Applications

China

MMLS3 Tyre contact

stresses being measured by SIM of CSIR

Refer de Beer and Sadzik SATC 2007

Salient Features of MMLS3 Testing that need to be borne in mind小型三分之一比例尺 MLS

Analysis of MMLS3 Performance

Stress PotentialStress Potential

Comparison of Vertical Compressive Stresses MMLS3 vs Trucks(Epps et al., WesTrack)

Deflection vs. speed under full-scale truck traffic

Comparison between some MMLS3 Results at different trafficking speeds

Fig. 9: Comparative summary of results

0

0.5

1

1.5

2

2.5

3

3.5

4

0 100 200 300 400 500 600 700 800 900 1000

Axles (x1000)

Ru

ttin

g (

mm

)

NCAT S9

Frankfort

Winburg

Winburg (km54)

Winburg slow

Power (NCAT S9)

Power (Frankfort)

Power (Winburg)

Power (Winburg (km54))

Power (Winburg slow)

Axles x1000

Rutting mm

1m

4mm

MMLS3 Testing in conjunction with the HVS on N4 near Pretoria 现场试验

MODIFIED BENKELMAN BEAM

BASE / SUBGRADE

Red Sand

HOT MIX ASPHALT (HMA)

ROLLER PERFORMANCE DURING CONSTRUCTION

0100200300400500600

0 2 4 6 8 10 12 14 16 18 20 22 24 26Number of roller passes

PS

PA

eff

ec

itiv

e s

tiff

ne

ss

M

Pa

0

100

200

300

400

500

600

86 88 90 92 94 96

% Compaction

PS

PA

eff

ec

tiv

e s

tiff

ne

ss

M

Pa

MONITORING EFFECTIVE STIFFNESS RELATIVE TO DENSITY OF COMPACTION

Construction of CTB

Test Site during construction!

MONITORING OF TRIAL SECTION STIFFNESS AFTER CONSTRUCTION

PSPA DATA ANALYSIS

Portable Seismic Pavement Analyzer便携式

P-SPA

First Correlations of Seismic Stiffness and Cracking

First Correlations of Seismic Stiffness and Cracking

First Correlations of Seismic Stiffness and Cracking

PSPA TIME RECORD

SHEAR WAVE VELOCITY: VS = VR ( 1.13 – 0.16v)

SHEAR MODULUS : G = ρ VS2

YOUNGS MODULUS : E = 2 ( 1 + v ) G

Response Model (after Jooste)

100

150

200

250

Ten

sile

Str

ain

(mic

rost

rain

) LET

FE (Static – Square loading area)

FE (20 km/h)FE (80 km/h)

Stiffness vs. HVS Reps (after Jooste)

Phase I: HVS test 425A5Upper subgrade resilient modulus at 40 kN

0

50

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150

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250

300

350

400

0 100 000 200 000 300 000 400 000 500 000 600 000 700 000 800 000

Repetitions

Res

ilien

t M

od

ulu

s (M

Pa)

MDD4 MDD8 MDD12

Load Setting / PSPA

Trafficking

Rut Measurements

NCAT field study Phase 2Core holes 在美国测试

NCAT HMA damaged by wet trafficking

Stiffness loss during trafficking of S9 NCAT 路面刚度损失

0%

20%

40%

60%

80%

100%

0 100 200 300 400 500 600 700

MMLS3 axles (Thousands)

Mod

ulus

rat

io

Wet SASW stiffness Young's Modulus vs. Load applications (30 Hz) in Texas

(See SAICE - 2002)

SASW after 10 million E80's

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0.2

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1.4

1.6

SECTION E2 E4 E6 E8

E10 N2 N4 N6 N8N10 N12 W

1W

3W

5W

7W

9 S1 S3 S5 S7 S9S11 S13

Test section

Trafficked vs Non-trafficked

Series1

Stiffness loss during trafficking of all NCAT sections

SASW NCAT after 10 Million E80s

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0.2

0.4

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0.8

1

1.2

1.4

1.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Surface Wave Test - NCSU

250

500

750

1000

1250

1500

0.E+00 1.E+05 2.E+05 3.E+05

Wheel Applications

Ph

ase

Vel

oci

ty,

Vp

h(m

/sec

)

0

10

20

30

40

50

Cra

ck L

eng

th (

m/m

)

MMLS3 (Vph) ALF (Vph)

MMLS3 (Crack Length) ALF (Crack Length)

Effect ofMicrocracking

Fatigue cracks NCSU

APT PERFORMANCE MONITORING IN LABORATORY

Relative stiffness ratios for MMLS3 and MLS10 – 7% CTB in lab and field

•

R2 = 0.589

R2 = 0.820

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1.1

0 200 400 600 800 1000 1200

AXLE LOAD IN 1 000's

RE

LA

TIV

E S

EIS

MIC

ST

IFF

NE

SS

RA

TIO

MMLS3 2.7 kN 700 kPa

MLS10 70 kN 800 kPa

Expon. (MMLS3 2.7 kN700 kPa)

Expon. (MLS10 70 kN800 kPa)

Full Scale Constructed Test Sections

SECTION SURFACING STABILIZING AGENT SAND TYPE CONSTRUCTION

NUMBER         TYPE

1 S2 Seal 5% CEMII 32.5 Red 1

2 40mm AC 5% CEMII 32.5 Red 1

3 60mm AC 5% CEMII 32.5 Red 1

4 40mm AC 5% CEMII 32.5 Red 2

5 40mm AC 2.5% CEMII 32.5 + 2.5% LIME Red 2

6 40mm AC 3.5% CEMII 32.5 + 3.5% LIME Yellow 2

7 40mm AC 7% CEMII 32.5 Yellow 2

8 40mm AC 7% CEMII 32.5 Red 2

9 S2 Seal 7% CEMII 32.5 Red 2

10 S2 Seal 5.5% SS60 Red 2

11 S2 Seal 1.5% CEMII 32.5 + 4% SS60 Red 2

Layout of

Test Sections

HVS and MMLS3 on R80 Pta West测试结果对比

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VERTICAL CONTACT STRESS PROFILES MMLS3 vs.HVS @ 750 kPa contact stress– 91%

(R80 Pta West)

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90

0 100 200 300 400 500 600 700 800

NORMAL STRESS IN KPA

DE

PT

H I

N m

m

MMLS3 2.9 KN 750 KPAHVS 40 KN 750 KPA CONTACT STRESS

SHEAR STRESS PROFILES MMLS3 vs. HVS @ 750 kPa contact stress–75%

(R80 Pta West)

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90

0 50 100 150 200 250 300

SHEAR STRESS IN kPA

DE

PT

H I

N m

m

MMLS3 2.9 KN 750 KPA

HVS 40 KN 620 KPA

MMLS3 Data Processing (R80 Pta West) Rutting - Extended Standard Mix vs Rut resistant mix

COMPARISION BETWEEN MMLS3 FIELD TESTS ON STANDARD AND RUT RESISTANT MIXES

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1

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7

0 100000 200000 300000 400000 500000 600000

LOAD APPLICATIONS

RU

T D

EP

TH

IN

mm

Q 2400 60 750 RUT RESISTANT J 2400 60 700 STANDARD

MMLS3 Data Processing (R80 Pta West) Rutting - Standard Mix vs Rut resistant mix

COMPARISION BETWEEN MMLS3 FIELD TESTS ON STANDARD AND RUT RESISTANT MIXES

y =

0.0525x0.3415

y =

0.0527x0.3451

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0 200000 400000 600000 800000 1000000 1200000

LOAD APPLICATIONS

RU

T D

EP

TH

IN

mm

Q 2400 60 750 RUT RESISTANT J 2400 60 700 STANDARD Power (Q 2400 60 750 RUT RESISTANT )Power (J 2400 60 700 STANDARD )

y = 0.0417x0.3674

y = 0.0439x0.3614

y = 0.0487x0.3498

y = 0.0525x0.3415

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0 100000 200000 300000 400000 500000 600000 700000 800000 900000 1000000

LOAD APPLICATIONS

RU

T D

EP

TH

IN

mm

TEST Q 50 K

TEST Q 100 K

TEST Q 150 K

TEST Q 200 K

Power (TEST Q 50 K)

Power (TEST Q 100K)

Power (TEST Q 150K)

Power (TEST Q 200K)

MMLS3 Data Processing (R80 Pta West) Extrapolation of Rutting Data:

0-50k; 0-100k; 0-150k; 0-200k = 12% difference

MMLS3 Data Processing (R80 Pta West) Rutting Profiles - Heave (left and right@ 450mm)

TEST Q POSITION 450 - 2.9 kN 750 kPa 2400 per Hour

-3

-2

-1

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TRANSVERSE POSITION IN mm

RU

T D

EP

TH

IN

mm

025005000100002500050000100000150000200000

Key to application of the MMLS3

Understanding APT:

• distress mechanisms• performance related factors

Applications MMLSMMLS3 Labs

USEurope

China

Africa

MMLS3 studies in global perspectiveMMLS3 studies in global perspective

MLS10 after completion of field trial on 25 yr old MLS10 after completion of field trial on 25 yr old untrafficked section of stiff HMA/CTB pavement in untrafficked section of stiff HMA/CTB pavement in

SwitzerlandSwitzerland 在瑞士量侧在瑞士量侧

A Concluding Note on APT modes结论

Slow , overloaded, uni- and bi-directional

Faster , uni-directional