Post on 06-Jul-2018
transcript
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Table of Contents
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6-8
9-13
14-26
27-39
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3-5Overview – Project location
Traffic – Existing vs Proposed
Pavement analysis tools
SH 286 – Analysis and limitations
FM 70 – Analysis and limitations
Conclusion
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2
3
4
5
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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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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
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Nondestructive pavement testing
Dynamic Cone Penetrometer
– Thickness verification
– More confidence in back-calculation
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SH 286 GPR
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Pavement surface
Bottom of HMAC @5.25”
Bottom of Base
8” base
HMAC: 5.24”
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SH 286 Depth check
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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
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< 4 ksi = Very poor subgrade
4 – 8 ksi = Poor subgrade
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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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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
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Flexbase modulus: 40 – 70 ksi
Lime stabilized base modulus: 60 – 75 ksi
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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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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
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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