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PAVEMENT ANALYSIS FOR WINDFARMSCorpus Christi District

10/10/2017

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Table of Contents

2

6-8

9-13

14-26

27-39

40

3-5Overview – Project location

Traffic – Existing vs Proposed

Pavement analysis tools

SH 286 – Analysis and limitations

FM 70 – Analysis and limitations

Conclusion

1

2

3

4

5

6

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OVERVIEWProject location

3

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Project location map

4

CR

59

CR

55

CR

49

SH

28

6

FM 70

FM 2444

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Project location map

5

CR

59

CR

55

CR

49

SH

28

6

FM 70

FM 2444

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MAIN CONCERN - TRAFFIC Existing traffic vs. wind farm traffic

6

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Traffic assessment

We performed a 7-day traffic classification study to obtain existing volume

and compare it to the development traffic volume

We used the 13-Category Scheme to classify vehicles

Heavy loads tend to damage a pavement more severely

The pavement damage caused by classifications 1 – 3 (motorcycles,

passenger cars, pickup trucks) is usually negligible

Most pavement damage comes from class 4 and higher

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Existing traffic vs. Wind farm development traffic

Existing Traffic

FHWA

CLASS TrafficMotorcycles 1 0.70%

Cars & trailer 2 50.40%

2 Axle Long 3 27.00%

Buses 4 0.70%

2 Axle 6 Tire 5 15.40%

3 Axle Single 6 0.20%

<5 Axle Double 8 2.20%

5 Axle Double 9 0.50%

Not classified N/A 2.80%

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Wind farm development

traffic

FHWA

CLASS

# of

trucksConcrete Trucks 7 16445

Gravel Trucks 8 12650

Controller Truck 9 253

Blade Delivery Truck 10 759

Nacelle Delivery Truck 13 253

Base Tower Delivery Truck 13 253

Mid/Top Tower Delivery Truck 13 506

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PAVEMENT ANALYSISLaboratory and non-destructive testing

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Laboratory testing

Soils/Base Testing

Tex 104, 5 & 6 – Plasticity index of soils – Soil PI is high (50 PI range)

Tex 110 – Particle size analysis of soils

Tex 113 – Laboratory compaction characteristics and moisture-density

relationship of base materials

Tex 116 – Ball mill method for determining the disintegration of flexible base

material – Flex base aggregate is weak

Tex 117 – Triaxial compression for base materials

HMA testing

Tex 207 – Determining density of compacted bituminous mixtures

Tex 227 – Theoretical maximum specific gravity

Tex 242 – Hamburg wheel-tracking test

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Nondestructive pavement testing

Ground Penetrating Radar (GPR)

– Layer thickness determination and uniformity

– Changes in section

– Defects in HMAC pavement

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Nondestructive pavement testing

Falling Weight Deflectometer (FWD)

– Measures deflection of pavement layers

– Elastic modulus back-calculation of pavement layers using Modulus 6

12

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Nondestructive pavement testing

Dynamic Cone Penetrometer

– Thickness verification

– More confidence in back-calculation

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SH 286Existing pavement analysis

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SH 286 – Typical section

15

XX

X = FWD tests

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SH 286 GPR

16

Pavement surface

Bottom of HMAC @5.25”

Bottom of Base

8” base

HMAC: 5.24”

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SH 286 Cores

17

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SH 286 Depth check

18

Limits of 18 ft. concrete pavement

9’ from centerline

6” HMAC

8” BASE

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FWD - Typical Moduli Values & Subgrade layer strength

Material Design Modulus (ksi)

Hot Mix Asphalt

Concrete

500

Flexible Base 40 – 70

Lime Stabilized Base 60 – 75

Concrete 2000 – 7000

Very good subgrade 16 – 20

Good subgrade 12 – 16

Average subgrade 8 – 12

Poor subgrade 4 – 8

Very poor subgrade 2 - 4

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SH 286 – Along centerline - Concrete pavement stiffness

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Typical concrete modulus: 2000 – 7000 ksi

Existing modulus: 2500 ksi (average)

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SH 286 – Widening stiffness – Subgrade

21

< 4 ksi = Very poor subgrade

4 – 8 ksi = Poor subgrade

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SH 286 – Widening stiffness – Flex Base

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Typical Flexbase modulus: 40 – 70 ksi

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EXISTING PAVEMENT LIMITATIONSSH 286

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SH 286 limitations

Subgrade back-calculated modulus is weak throughout the entire section

which could lead to failures by heavy loads.

Subgrade modulus of 4 ksi is classified as very poor subgrade.

Axle load distribution between concrete and flexible base could lead to

failure of widened section.

The Modified Texas Triaxial Design Method based on 12,000 lb wheel load

– Widening is not thick enough to provide protection for the proposed loads

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Pavement condition of SH 286 between FM 2444 and FM 70

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Pavement condition of SH 286 north of FM 2444

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FM 70Existing pavement analysis

27

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FM 70– Typical section

28

X

X = FWD tests

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FM 70 Cores

29

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FM 70 Depth Check

30

APPROX. 18” BASE

-10” LTB

-8” LTSB

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FM 70 Subgrade stiffness

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Average subgrade: 8 – 12 ksi

Existing modulus: 11.5 ksi

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FM 70 Base stiffness

32

Flexbase modulus: 40 – 70 ksi

Lime stabilized base modulus: 60 – 75 ksi

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EXISTING PAVEMENT LIMITATIONSFM 70

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FM 70 limitations

FM 70 is a load-restricted highway, it has a Gross Vehicle Weight (GVW) limit

of 58,420 pounds.

– These facilities were designed for lighter wheel loads and axle

configurations than are currently allowed by law.

Base is weak at some pavement sections which could lead to failures by

heavy loads

The Modified Texas Triaxial Design Method based on 12 kip wheel load

– FM 70 is not thick enough to provide protection for the proposed loads

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FM 70 – Potential failures based on FWD drops – 3.3 miles

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FM 70 – Potential failures based on FWD drops – 2.4 miles

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FM 70 – Potential failures based on FWD drops – 1.8 miles

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FM 70 – Potential failures based on FWD drops – 0.9 miles

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Cost to repair potential failures on FM 70

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$132,422.18

$264,844.36

$353,125.82

$485,548.00

$260,650.64

$521,301.27

$695,068.36

$955,719.00

$393,072.82

$786,145.64

$1,048,194.18

$1,441,267.00

0.9 miles

1.8 miles

2.4 miles

3.3 miles

Cost estimate per section Average low bid prices for Corpus Christi District:

HMAC @ $76/Ton

Flex base @ $68/Cubic Yard

Total cost 6" FL BS cost 2" HMAC cost

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Conclusion

40

Visual evaluation and documentation of existing pavement distress

Run FWD to determine if road is structurally sound and identify weak spots

What are our options??

Await and asses damage after development

Address weak spots or place a structural overlay

Negotiate a donation agreement to maintain the roadway during development

Insufficient pavement thickness to

provide protection from heavy

loads based on the Texas Triaxial

Check

Subgrade on SH 286 is classified

as very weak, which could lead to

failure of widened section

Sections of FM 70 were identified

with low strength on base section

which could lead to failures

5” structural overlay to meet TTC

requirements (not feasible)

too expensive

subgrade is weak

Move heavy loads along centerline

within the limits of the concrete

pavement

Needs traffic control

Safety

2” structural overlay

$150K per mile

Spot repairs to address weak

spots

$400K - $1.4M

Negotiate a donation agreement

with developer to address failures

as they occur

Existing Pavement Limitations SH 286 - Alternatives FM 70 - Alternatives