Effects of Heavy Farm Equipment

on Pavement Performance

Pooled Fund TPF-5(148)

Jason Lim

Andrea Azary

Lev Khazanovich

University of Minnesota

October 4, 2011

Background Participants:

IL DOT

Industries Represented by Professional Nutrient Applicators Association of Wisconsin (PNAAW)

Iowa DOT

Minnesota Local Road Research Board (LRRB)

MnDOT

Private Industry: WI manure applicator association

John Deere

Professional Dairy Producers Of Wisconsin

Husky Farm Equipment

Minnesota Custom Manure Applicators Association

Michelin Tire

University of Minnesota and Iowa State University

Objectives

Determine pavement responses generated

by heavy agricultural equipments

Compare measured responses to a typical

5-axle semi truck

Develop models to evaluate pavement

damage from heavy vehicles

Research Approach Constructed two asphalt test sections

on MnROAD research facility (A & B)

B A

Existing PCC section on MnROAD

Section 54

7.5 PCC

12 aggregate base

Cell 84 (Thick)

5.5 HMA with PG58-34;

9 gravel aggregate base over

A-4 subgrade soil (existing subgrade soil).

Cell 83 (Thin)

3.5 HMA with PG58-34;

8 gravel aggregate base over

A-4 subgrade soil (existing subgrade soil).

Tested Vehicles Vehicle ID Type Vehicle Make

S4 Straight Truck Homemade

S5 Straight Truck Homemade

S3 Terragator AGCO Terragator 8204

R4 Terragator AGCO Terragator 9203

R5 Terragator AGCO Terragator 8144

R6 Terragator AGCO Terragator 3104

T1 Tanker John Deere 8430 w/ Houle tank

T2 Tanker M. Ferguson 8470 w/ Husky tank

T6 Tanker John Deere 8230 w/ Husky tank

T7 Tanker Case IH 335 with Houle tank

T8 Tanker Case IH 335 with Houle tank

G1 Grain Cart Case IH 9330 with Parker 938 cart

Mn80 Semi Truck Navistar

Mn102 Semi Truck Mack

Tested Vehicles

Test Statistics

Test Season Test Dates Vehicle Passes

AC PCC

Spring 2008 March 17th

19th

& 24th

26th

400 48

Fall 2008 August 26th

29th

282 72

Spring 2009 March 16th

20th

960 170

Fall 2009 August 24th

28th

782 360

Spring 2010 March 15th

18th

776 344

Fall 2010 August 18th

19th

426 204

Total 3,626 1,198

Traffic Wander Measurement

Structural Response Measurement

(stresses and strains)

Peak-Pick Analysis

Tekscan

0%

7,980 lbs

50%

19,550 lbs

80%

24,680 lbs

Summary of Results

Cell 83 (3.5-in asphalt concrete [AC]

section) failed in S09 (WB lane) and in

F09 (EB lane); cell 84 (5.5-in AC section)

has not shown significant distresses.

Failure started at the location with a

thinner AC thickness (about 2.5 in), but

propagated several yards in both

directions. Due to continued heavy

trafficking of failed areas, a portion of cell

83 was damaged beyond repair.

Summary of Results (cont.)

All tested vehicles resulted in higher subgrade

stresses than the standard truck.

Pavement damage is governed by axle

weight, not the gross vehicle weight.

Therefore, it is important to ensure even load

distribution among axles.

.

Measured Maximum Subgrade Stresses

Normalized to Mn80 Subgrade Stress

Cell 84, 80 percent loading

Effect of Vehicle Weight

(Number of Axles) Fall 2009

T6, John Deere 8230, 6000 gal

100% loading: 60.0 kip (26.5 and 33.5 kip)

T7, Case IH 335, 7300 gal

100% loading: 79.5 kip (26.3, 26.2, and 26.0 kip)

T8, Case IH 335, 9500 gal

100% loading: 94.2 kip (23.3, 23.7, 23.5, and

23.7 kip)

Effect of Number of Axles

T6 resulted in higher sugrade stresses!

Summary of Results (cont.)

Presence of a paved shoulder reduces

damage potential. In the absence of a paved

shoulder, allowing to drive in the middle of

roads (away from the edge) reduces a risk of

pavement failure.

Pavement damage can be reduced if the most

unfavorable conditions (fully saturated and/or

thawed base and subgrade, high AC

temperature) are avoided.

R5 Subgrade Stress (84PG4) 80% S09

0

5

10

15

20

-10 -5 0 5 10 15 20 25

Rear axle relative offset [in]

Str

ess [

psi]

AM

PM

R5 Subgrade Stress (83PG4) 80% S09

0

5

10

15

20

-10 -5 0 5 10 15 20 25

Rear axle relative offset [in]

Str

ess [

psi]

AM

PM

Pavement Structure

Time of Testing Mn80 AC Strain (84LE4) F09

0

100

200

300

400

500

600

-25 -15 -5 5 15 25

Rear axle relative offset [in]

Str

ain

[10

-6]

AM

PM

Mn80 Subgrade Stress (84PG4) F09

0

2

4

6

8

10

12

14

-25 -15 -5 5 15 25

Rear axle relative offset [in]

Str

ess [

psi]

AM

PM

Time of Testing AC Strain (84LE4) 100% F09

0

100

200

300

400

500

600

700

Mn102 Mn80 R5 T6 T7 T8

Vehicles

Str

ain

[10

-6]

AM

PM

Subgrade Stress (84PG4) 100% F09

0

5

10

15

20

25

Mn102 Mn80 R5 T6 T7 T8

Vehicles

Str

ess [

psi]

AM

PM

Early Fall vs Late Fall

0

5

10

15

20

-40 -20 0 20

Su

bg

rad

e S

tre

ss

(p

si)

Relative Offsets (in)

T6 November 2010 Mn80 November 2010

T6 August 2010 Mn80 August 2010

Damage Modeling

Structural Model Layered Elastic Analysis

Asphalt layer

12-in thick base

Subgrade

Apparent stiff layer

Tekscan data converted into multiple

circular footprints

Vehicle T7

tractor axle

Structural Model Layered Elastic Analysis

Asphalt layer

12-in thick base

Subgrade

Apparent stiff layer

Tekscan data converted into multiple

circular footprints

Vehicle T7

tractor axle

Critical Responses

Asphalt strains

Subgrade strains

Base displacements

Base mid-depth shear stresses

Critical Responses

Relative Calculation

Subgrade rutting damage

AC cracking relative damage

crackingvehicle

crackingSA

N

Nreldamage

,

,18

vehicle

SA

N

Nreldamage 18

Base compression

Base shear failure

bRDDtop

ABASECOMP

12

3

s

crtitcalRSR

1

,1

Early Spring Season

100% Loading 1

,1 crtitcalSR

Vehicle Cell 83 Cell 84 R4 0.9405 1.0815

S3 0.9248 1.1005

S4 0.8536 1.058

S5 0.8738 1.0792

T6 0.9074 1.0597

T7 0.9526 1.1175

T8 0.864 1.0685

Mn80 0.8877 1.1329

Mn102 0.841 1.0703

T1 0.8692 1.057

T2 0.9246 1.1267

Differential Deflection Index

Early Spring Season 100% Loading

Vehicle Cell 83 Cell 84 R4 0.8847 1.3249

S3 1.0941 1.7047

S4 1.0169 1.7173

S5 1.0371 1.7703

T6 0.8026 1.3124

T7 1.0455 1.6985

T8 1.0316 1.7429

Mn80 1.3356 2.2877

Mn102 1.0688 1.8356

T1 0.8954 1.5096

T2 1.1785 2.0061

Cell 83

All the vehicles exhibited SR less than 1

Many vehicles exhibited SR less than 0.9

Several vehicles exhibited DDI less than 1

Cell 84

None of the vehicles exhibited SR less than 1

even for 100 percent load level

None of the vehicles exhibited DDI less than

1.3 even for 100 percent load level

It is quite likely that large shear stresses

or compressive deflections in the base layer

caused failure of Cell 83.

Effect of AC Thickness

on Rutting Damage

from Heaviest Axle

Effect of AC Thickness

on SR

Kevin Erbs Problem

I have 1,000,000 gallons of product that

needs to be moved. Which vehicle is the

least damaging?

2 roads: 7-TONN road and 10-TONN road

Design life: 20 years

The product is moved every year

Location: Anoka Co., MN

MnPAVE

MnPAVE Analysis

7-TONN road (3.5-in thick AC pavement )

Allowable number of ESALs

AC fatigue: 1,400,000

Subgrade rutting: 320,000

10-TONN road (5.5-in thick AC pavement )

Allowable number of ESALs

AC fatigue: 13,400,000

Subgrade rutting: 940,000

Estimated Product Weights in

One Move

Vehicle

Net Weight,

lbs

Number of

Passes

S4 32,549* 5,100

S5 39,410* 4,212

T6 49,790 3,334

T7 60,100 2,762

T8 76,000 2,184

T1 47,475* 3,497

T2 17,882* 9,283

Net weight = 100% load 0% load

*estimated

7-TONN ROAD, Asphalt Damage

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35D

am

ag

e

Vehicle

7-TONN ROAD, Subgrade Damage

may cause failure in early spring

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Dam

ag

e

Vehicle

10-TONN ROAD, Asphalt Damage

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Dam

ag

e

Vehicle

10-TONN ROAD, Subgrade Damage

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Dam

ag

e

Vehicle