Assessment of Falling Weight Deflectometer Data for Stabilized Flexible Pavements

Abstract

Backcalculation of pavement moduli through the utilization of the falling weight deflectometer (FWD) is used for pavement monitoring and evaluation. The performance and structural condition of nine flexible pavement test sections built in Bedford County, Virginia, have been monitored over the past 5 years using FWD. The nine sections include three groups with aggregate base layer thicknesses of 100, 150, and 200 mm, respectively. Sections 1, 4, and 7 are control, whereas Sections 2, 5, 8 and 3, 6, 9 are stabilized with geotextiles and geogrids, respectively. The FWD testing used five double-load drops ranging from 26.5 to 58.9 kN. The deflection basins obtained from the testing have been analyzed using the ELMOD backcalculation program to find the pavement structural capacity and to detect changes in the aggregate resilient modulus. The analysis shows a reduction in the backcalculated resilient modulus of the 100-mmthick base layer. The reduction was 33 percent over 5 years for the nonstabilized section compared with the geosynthetically stabilized section. The reduction in base layer resilient modulus may have resulted from subgrade fine migration into this layer as confirmed by excavation. The study confirms the effectiveness of using woven geotextile as a separator in a pavement system built over weak subgrade. This supports the continuous rutting measurements and ground truth excavation conducted in late 1997.

Get full access to this article

View all access options for this article.

References

Al-Qadi

I. L.

, Brandon

T. L.

, Valentine

R. J.

, Lacina

B. A.

, and Smith

T. E.

. Laboratory Evaluation of Geosynthetic-Reinforced Pavement Sections. In Transportation Research Record 1439, TRB, National Research Council, Washington, D.C., 1994, pp. 25–31.

Al-Qadi

I. L.

, Brandon

T. L.

, and Bhutta

S. A.

. Geosynthetically Stabilized Flexible Pavement. Geosynthetics ’97, Long Beach, Calif., 1997, pp. 647–662.

Guram

, Marienfeld

, and Hayes

. Evaluation of Nonwoven Geotextile Versus Lime-Treated Subgrade in Atoka County, Oklahoma. In Transportation Research Record 1439, TRB, National Research Council, Washington, D.C., 1994, pp. 7–11.

Austin

D. N.

, and Coleman

D. M.

. A Field Evaluation of Geosynthetic-Reinforced Haul Roads over Soft Foundation Soils. Geosynthetics ’93, Vancouver, British Columbia, Canada, 1993, pp. 65–80.

Laier

, and Brau

. The Use of Geotextiles in Road Construction Under Intensive Dynamic Loading. Third International Conference on Geotextiles, Vienna, Austria, 1986, pp. 995–1000.

Christopher

B. R.

, and Holtz

R. D.

. Geotextile Engineering Manual. Report FHWA-TS86/203. Federal Highway Administration, U.S. Department of Transportation, 1985.

Jorenby

B. N.

, and Hicks

R. J.

. Base Course Contamination Limits. In Transportation Research Record 1095, TRB, National Research Council, Washington, D.C., 1986, pp. 86–101.

Koerner

R. M.

Designing with Geosynthetics, 3rd ed. Prentice Hall, Inc., Englewood Cliffs, N.J., 1994.

Brandon

T. L.

, Al-Qadi

I. L.

, Lacina

B. A.

, and Bhutta

S. A.

. Construction and Instrumentation of Geosynthetically Stabilized Secondary Road Test Sections. In Transportation Research Record 1534, TRB, National Research Council, Washington, D.C., 1996, pp. 50–57.

10.

Al-Qadi

I. L.

, Brandon

T. L.

, Bhutta

S. A.

, and Appea

A. K.

. Field Testing of Geosynthetically Stabilized Pavement Sections. Virginia Tech, Blacksburg, 1996.

11.

Parker

Jr. , Estimation of Paving Materials Design Moduli from Falling Weight Deflectometer Measurements. In Transportation Research Record 1293, TRB, National Research Council, Washington, D.C., 1991, pp. 42–51.

12.

Rada

G. R.

, Richter

C. A.

, and Jordahl

. SHRP’s Layer Moduli Backcalculation Procedure. In Nondestructive Testing of Pavements and Backcalculation of Moduli. ASTM STP 1198, American Society for Testing and Materials, Philadelphia, Pa., 1994, pp. 38–53.

13.

Lytton

R. L.

Backcalculation of Pavement Layer Properties. In Nondestructive Testing of Pavements and Backcalculation of Moduli. ASTM STP 1026, American Society for Testing and Materials, Philadelphia, Pa., 1989, pp. 7–38.

14.

Appea

A. K.

, Al-Qadi

I. L.

, Bhutta

S. A.

, and Coree

B. J.

. Quantitative Assessment of Transition Layer in Flexible Pavements. Presented at the 77th Annual Meeting of the Transportation Research Board, Washington, D.C., 1998.

15.

Ullidtz

, Battiato

, Larsen

B. K.

, and Stubstad

R. N.

. Verification of the Analytical-Empirical Method of Pavement Evaluation Based on FWD Testing. Proc., 6th International Conference on Structural Design of Asphalt Pavements, University of Michigan, Ann Arbor, Vol. 1, 1987, pp. 521–532.

16.

Ullidtz

, and Peattie

K. R.

. Pavement Analysis by Programmable Calculators. Transportation Engineering Journal of the ASCE, Vol. 106, No. TE5, Sept. 1980.

17.

Baltzer

, and Jansen

J. M.

. Temperature Correction of Asphalt Moduli for FWD Measurements. Proc., 4th International Conference on the Bearing Capacity of Roads and Airfields, University of Minnesota, Vol. 1, 1994.