pavement design - ss

39
Pavement Design

Upload: awang-ar

Post on 30-Sep-2015

238 views

Category:

Documents


1 download

DESCRIPTION

Pavement Design in Slide Show

TRANSCRIPT

  • Pavement Design

  • I. Pavement Design A. OverviewPrincipal cause of pavement failure shown abovenot the blacktopDegree of curvature

  • I. Pavement Design B. California Bearing Ratio (CBR)

    How to build a road!

  • I. Pavement Design B. California Bearing Ratio (CBR)1. The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses. It was developed by the California Department of Transportation.

  • I. Pavement Design B. California Bearing Ratio (CBR)The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses. It was developed by the California Department of Transportation.

    2. The test is performed by measuring the pressure required to penetrate a soil sample with a plunger of standard area. The measured pressure is then divided by the pressure required to achieve an equal penetration on a standard crushed rock material.

  • I. Pavement Design B. California Bearing Ratio (CBR)3. The Test

    Take load readings at penetrations of: the result 0.025 70 psi0.05...115 psi0.1.220 psi0.2.300 psi0.4.320 psiPenetrations of 0.05 per minuteAchieve OM &MD6 mold

  • 4. Plot the Data

    Chart1

    70

    115

    220

    300

    320

    Penetration (inches)

    Load on Piston (psi)

    Sheet1

    0.02570

    0.05115

    0.1220

    0.2300

    0.4320

    Sheet2

    Sheet3

  • 5. Determine the percent of compacted crushed stone values for the 0.1 and 0.2penetration.The Gold Standard for CBR for 0.1 of penetration, 1000 psi for 0.2 of penetration, 1500 psiExample above: for 0.1 of penetration, 220 psi for 0.2 of penetration, 300 psiThe standard material for this test is crushed California limestone

    Chart1

    70

    115

    220

    300

    320

    Penetration (inches)

    Load on Piston (psi)

    Sheet1

    0.02570

    0.05115

    0.1220

    0.2300

    0.4320

    Sheet2

    Sheet3

  • 5. Determine the percent of compacted crushed stone values for the 0.1 and 0.2penetration.The Gold Standard for CBR for 0.1 of penetration, 1000 psi for 0.2 of penetration, 1500 psiExample above: for 0.1 of penetration, 220 psi for 0.2 of penetration, 300 psiExample psi = CBRStandard psi220 psi = .22, or 22%1000 psi300 psi = .20, or 20%1500 psiCBR of material = 22%

    Chart1

    70

    115

    220

    300

    320

    Penetration (inches)

    Load on Piston (psi)

    Sheet1

    0.02570

    0.05115

    0.1220

    0.2300

    0.4320

    Sheet2

    Sheet3

  • 5. Determine the percent of compacted crushed stone values for the 0.1 and 0.2penetration.The Gold Standard for CBR for 0.1 of penetration, 1000 psi for 0.2 of penetration, 1500 psiExample above: for 0.1 of penetration, 220 psi for 0.2 of penetration, 300 psiExample psi = CBRStandard psi220 psi = .22, or 22%1000 psi300 psi = .20, or 20%1500 psiCBR of material = 22%Use 0.1 of penetration, unless 0.2 is the greater value.If so, then rerun the test, taking the higher of the two values from this second trial

    Chart1

    70

    115

    220

    300

    320

    Penetration (inches)

    Load on Piston (psi)

    Sheet1

    0.02570

    0.05115

    0.1220

    0.2300

    0.4320

    Sheet2

    Sheet3

  • 5. Determine the percent of compacted crushed stone values for the 0.1 and 0.2penetration.The Gold Standard for CBR for 0.1 of penetration, 1000 psi for 0.2 of penetration, 1500 psiExample above: for 0.1 of penetration, 220 psi for 0.2 of penetration, 300 psiExample psi = CBRStandard psi220 psi = .22, or 22%1000 psi300 psi = .20, or 20%1500 psiCBR of material = 22%, or 22In General:The harder the surface, the higher the CBR rating. A CBR of 3 equates to tilled farmland, A CBR of 4.75 equates to turf or moist clay, Moist sand may have a CBR of 10. High quality crushed rock has a CBR over 80.The standard material for this test is crushed California limestone which has a value of 100.

  • Potential Corrections to the Stress-Penetration Curves

    Chart1

    70

    115

    220

    300

    320

    Penetration (inches)

    Load on Piston (psi)

    Sheet1

    0.02570

    0.05115

    0.1220

    0.2300

    0.4320

    Sheet2

    Sheet3

  • I. Pavement Design C. The Mechanics of the Design

  • I. Pavement Design C. The Mechanics of the DesignDetermineThe CBR values of the subgradeThe type of use expected (runways vs. taxiways)

  • I. Pavement Design C. The Mechanics of the DesignDetermineThe CBR values of the subgradeThe type of use expected (runways vs. taxiways)The expected wheel load during serviceTypes of CBR materials available for the construction

  • I. Pavement Design C. The Mechanics of the Design2. Primary GoalsTotal strength of each layer only as good as what is beneath itTherefore, must meet minimum thickness requirementsDont break the bankUse less inexpensive CBR materials when allowed while not shortchanging the projects integrity

  • I. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)?

  • a point on the curve for agiven CBR material representsthe minimum thickness ofpavement courses that willreside above it, in order tomaintain stability

  • CBR subbase of 8,Taxiway, and wheel load of 40,000 lb23 inches23 inches of total earth materialand pavement

  • I. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)

    What is the optimal pavement thickness (wearing surface)?What is the optimal CBR value of upper 6 inches?

    23 inches

  • I. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)

    What is the optimal pavement thickness (wearing surface)?What is the optimal CBR value of upper 6 inches?

    Wheel Pound LoadsCBR Value 15,000 or less50 15k-40k65 40k-70k80 70k-150k80+Wearing Surface0-15k.....2>15k-40k..3>40k-55k..4>55k-70k..5>70k..6

  • I. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)

    What is the optimal pavement thickness (wearing surface)?What is the optimal CBR value of upper 6 inches?

    Wheel Pound LoadsCBR Value 15,000 or less50 >15k-40k65 >40k-70k80 >70k-150k80+Wearing Surface0-15k.....2>15k-40k..3>40k-55k..4>55k-70k..5>70k..623 inches3 inches6 inches of CBR 65/80

  • V. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)

    What is the optimal pavement thickness (wearing surface)?What is the optimal CBR value of upper 6 inches?

    Wheel Pound LoadsCBR Value 15,000 or less50 >15k-40k65 >40k-70k80 >70k-150k80+Wearing Surface0-15k.....2>15k-40k..3>40k-55k..4>55k-70k..5>70k..623 inches3 inches6 inches of CBR 65/80CBR = 8036

  • V. Pavement Design C. The Mechanics of the Design3. An exampleA compacted subgrade has a CBR value of 8. What is the minimum pavement thickness if it is to support a taxiway pavement designed to support a 80,000 lb airplane (40,000 wheel load)

    What is the optimal pavement thickness (wearing surface)?What is the optimal CBR value of upper 6 inches?What can we use for the remainder of thickness?

    Wheel Pound LoadsCBR Value 15,000 or less50 >15k-40k65 >40k-70k80 >70k-150k80+Wearing Surface0-15k.....2>15k-40k..3>40k-55k..4>55k-70k..5>70k..623 inches3 inches6 inches of CBR 65/80CBR = 8036

  • Need = 9 minimum thickness

  • CBR = 27 for remainder of base(14)

  • Given: Same CBR subgrade as before

    Materials available of:CBR=30, 80

    Determine:Optimal thickness of each layer while minimizing costs

  • Given: Same CBR subgrade as before

    Materials available of:CBR=30, 80

    Determine:Optimal thickness of each layer while minimizing costsCBR of 30 needs minimum of 9of pavement courses above it.

  • Given: Same CBR subgrade as before

    Materials available of:CBR=30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

    CBR of 30 needs minimum of 9of pavement courses above it.

  • Given: Same CBR subgrade as before

    Materials available of:CBR=30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 614 of CBR 30CBR of 30 needs minimum of 9of pavement courses above it.

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

    A CBR of 15 requires X above it

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

    A CBR of 15 requires 15 above it

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

    A CBR of 15 requires 15 above itA CBR of 30 requires X above it

  • Another Example:Given: Same CBR subgrade as before

    Materials available of:CBR=15, 30, 80

    Determine:Optimal thickness of each layer while minimizing costs3 of wearing surface6 of CBR 80 in upper 6

    A CBR of 15 requires 15 above itA CBR of 30 requires 9 above it

  • Your turn.

    Subbase of CBR=7,50,000 lb loads for a taxiwayCBR materials available: 80, 30, 15

    Design the pavement with attention paid to optimizing costs and stability

  • Your turn.

    Sub base of CBR=7,50,000 lb loads for a taxiwayCBR materials available: 80, 30, 15

    Design the pavement with attention paid to optimizing costs and stabilitySolution:Total Thickness: 28Wearing Surface Thickness: 4Upper 6 of CBR=80CBR 30 of 7CBR 15 of 11

  • Homework:

    Subbase of CBR=15,70,000 lb loads for a runwayCBR materials available: 80, 40, 20

    Design the pavement with attention paid to optimizing costs and stability

    ***************************************