Evaluation of the Rolling Wheel Deflectometer (RWD) in Louisiana John Ashley Horne Dr. Mostafa A Elseifi
Introduction Louisiana uses the Falling-Weight Deflectometer (FWD) for project level testing Limitations of FWD at the network level: Costly and slow testing process Discrete testing of the pavement network Delays to the public due to lane closures Safety of highway workers during testing
Overview Overview of RWD Field testing program Present collected RWD and FWD data Comparison of RWD and FWD data 3
Rolling Wheel Deflectometer Test at traffic speed (up to 60mph) Measures center pavement deflection to vehicle loading Final prototype introduced in 2003 but has never been tested in Louisiana (RWD) 1/20/2011 4
Rolling Wheel Deflectometer Deflection- Measurement System Heating/Cooling System 53ft Steel-Loading Plates 1/20/2011 5
Rolling Wheel Deflectometer Data Collection Vehicle Lasers
Rolling Wheel Deflectometer Data Collection Vehicle Distance Measuring Instrument (DMI)
Rolling Wheel Deflectometer Calibration
Field Testing Plan Testing program was conducted over two phases: Phase I: RWD testing of the complete asphalt road network (about 1500 miles) in District 5 Phase II: Detailed RWD evaluation in District 5 16 test sites were tested using RWD FWD testing conducted within 24 hrs of RWD testing 1/20/2011 9
Rolling Wheel Deflectometer Phase I Network Testing UNION MOREHOUSE WEST CARROLL EAST CARROLL LINCOLN OUACHITA RICHLAND MADISON JACKSON
Field Testing Plan Phase II Research Sites 1/20/2011 11
Field Testing Plan Site ID Pavement Type Subgrade/Base Type AADT CPI (2009) Condition- CPI IRI (2009) 1 HMA Granular 1,185 81 good 81.3 2 HMA Granular 2,585 92 good 92.1 3 HMA Stabilized 6,398 99 very good 98.9 4 HMA Stabilized 244 N/A very good N/A 5 HMA Stabilized 3,490 98 very good 97.2 6 HMA Stabilized 5,623 99 very good 97.8 7 Composite Granular 29,357 97 very good 95.8 8 HMA Granular 6,409 70 fair 80.1 9 HMA Stabilized 3,859 99 very good 98.5 10 HMA Granular 650 64 poor 74.3 11 HMA Stabilized 800 57 poor 48.3 12 HMA Stabilized 1,898 77 fair 71.5 13 HMA Stabilized 7,017 87 good 90.2 14 Composite Granular 2,963 63 poor 69.6 15 S. Treated Stabilized 424 82 good 69.7 16 S. Treated Stabilized 244 60 poor 58.5 1/20/2011 12
Field Testing Plan - RWD Triplicate runs conducted on each site Five test speeds: 20, 30, 40, 50, and 60 mph High speed not possible on secondary roads Field testing conducted in December 2009 Temperature ranged from 29 to 68F Pavement temperature recorded during testing Deflection shifted to 68F using the BELLS method 1/20/2011 13
Field Testing Plan - FWD FWD testing was conducted at a spacing of 0.06 km in the middle of the averaging interval used in RWD testing. Three load levels of 40, 53, and 66 kn were used in the FWD deflection-testing program.
Data Processing and Filtering Laser deflection readings are measured at 15-mm intervals Irrelevant data (bridge, sharp curves, and at traffic signals) were removed Erroneous data may be obtained if pavement is wet or severely cracked 1/20/2011 15
Data Processing Valid deflection measurements were averaged every 0.1 mile (average of 10,728 individual readings) 30 Averaging Interval 6 Deflection, mils 25 20 15 10 As averaging length decreases, deflection variability increases 528 ft 132 ft 33 ft Standard deviation of means, mils 4 2 An averaging length of 528 ft is recommended for PMS applications to reduce random error to approximately 1 mil 5 0 6 6.5 7 7.5 Logmile 0 0 100 200 300 400 500 600 Interval length, ft 1/20/2011 16
Repeatability Analysis 25 20 15 10 5 0 Run 1 Run 2 Run 3 Mean 2.013 2.088 2.163 2.238 2.312 2.388 2.463 2.538 2.613 2.688 2.763 2.838 2.912 2.988 3.063 3.138 3.213 3.288 3.363 3.438 Deflection (mils) Station (mile) Site 4 Newly Constructed in 2009 1/20/2011 17
Repeatability Analysis 25 20 15 10 5 0 Run 1 Run 2 Run 3 Mean 6.288 6.362 6.438 5.013 5.088 5.162 5.238 5.313 5.388 5.463 5.538 5.612 5.688 5.763 5.838 5.913 5.988 6.063 6.138 6.213 Station (mile) Site 6 CPI = 99 1/20/2011 18 Deflection (mils)
Repeatability Analysis Deflection (mils) 30 25 20 15 10 5 0 Run 1 Run 2 Run 3 Mean Station (mile) Site 8 CPI = 70 1/20/2011 19
Repeatability Analysis 40 35 30 25 20 15 10 5 0 Run 1 Run 2 Run 3 Mean Bridge Bridge 6.188 6.263 6.338 4.913 4.988 5.063 5.138 5.213 5.288 5.362 5.438 5.513 5.588 5.662 5.738 5.813 5.888 5.963 6.038 6.112 Station (mile) Site 11 CPI = 57 1/20/2011 20 Deflection (mils)
Coefficient of Variation (%) Repeatability Analysis COV ranged from 6 to 20% with an average of 15% Measurements were more scattered in sites in poor condition, than in sites in good conditions 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Site ID 1/20/2011 21
Effect of Testing Speed Avg. Deflection (mm) The influence of the testing speed on the measured deflection was minimal Deflections data obtained at different speeds may be comparable 700 600 500 400 300 200 100 0 32 kph 48 kph 64 kph 80 kph 96 kph 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Site ID 1/20/2011 22
1.800 1.600 Site 1 Fair Site 2 Good Site 3 Very Good 1.400 1.200 Deflection (mm) 1.000 0.800 0.600 RWD FWD 0.400 0.200 0.000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 Station (km) 1/20/2011 23
1.200 Site 8 Fair Site 9 Very Good Site 10 Poor 1.000 0.800 0.600 0.400 RWD FWD 0.200 0.000 3.220 3.500 3.780 4.060 4.340 4.620 4.900 5.180 5.460 9.660 9.940 10.220 10.500 10.780 11.060 11.340 11.620 11.900 3.063 3.238 3.413 3.588 3.763 3.938 4.113 4.288 4.463 Station (km) 1/20/2011 24 Deflection (mm)
FWD vs. RWD Site ID Average FWD (mils) Average RWD (mils) Pearson Correlation P-value Decision 1 24.83 18.20 0.13 < 0.0001 Not Equal 2 9.58 15.79 0.65 < 0.0001 Not Equal 3 6.76 11.78 0.78 < 0.0001 Not Equal 4 7.44 15.62 0.22 < 0.0001 Not Equal 5 6.51 9.50 0.41 < 0.0001 Not Equal 6 8.97 14.99 0.66 < 0.0001 Not Equal 7 1.66 7.75 0.15 < 0.0001 Not Equal 8 10.88 15.48 0.59 < 0.0001 Not Equal 9 4.99 8.34 0.20 < 0.0001 Not Equal 10 14.58 14.01 0.44 0.19 Equal 11 26.83 19.89 0.38 < 0.0001 Not Equal 12 11.58 18.41 0.44 < 0.0001 Not Equal 13 4.41 9.51 0.22 < 0.0001 Not Equal 14 8.34 14.37 0.14 < 0.0001 Not Equal 15 12.02 13.54 0.35 0.003 Not Equal 16 37.72 21.55 0.06 < 0.0001 Not Equal 1/20/2011 25
FWD vs. RWD Average FWD Center Deflection (mils) 40 35 30 25 20 15 10 5 0 Speed 20 mph y = 0.8198e 0.1683x R² = 0.78 0 10 20 30 Average RWD Deflection (mils) Average FWD Center Deflection (mils) 40 35 30 25 20 15 10 5 0 Speed 30 mph y = 1.0783e 0.1544x R² = 0.78 0 10 20 30 Average RWD Deflection (mils) Average FWD Center Deflection (mils) 40 35 30 25 20 15 10 5 0 Speed 40 mph y = 1.493e 0.1259x R² = 0.61 0 10 20 30 Average RWD Deflection (mils) Average FWD Center Deflection (mils) y = 0.8156e 0.1891x R² = 0.82 1/20/2011 26 40 35 30 25 20 15 10 5 0 Speed 50 mph 0 10 20 30 Average RWD Deflection (mils)
Findings and Summary Repeatability of RWD measurements was acceptable - average COV at all test speeds of 15%. Measurements were more scattered in sites in poor condition, than in sites in good conditions The influence of the testing speed on the measured deflections was minimal 1/20/2011 27
Findings and Summary The scattering and uniformity of the FWD and RWD data appears to follow closely the conditions of the roadway. RWD deflection measurements were in general agreement with FWD deflections measurements The mean center deflections from RWD and FWD were statistically different for 15 of the 16 sites 1/20/2011 28
Questions