Subgrade Resilient Modulus Correction for Saturation Effects
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 123, Issue 7
Abstract
Mechanistic design methods for flexible pavement require the specification of the resilient modulus Mr for each soil subgrade encountered in the pavement project. The resilient modulus is usually measured in the laboratory under conditions of maximum dry density and optimum water content to reflect the conditions under which subgrades are usually prepared. To account for the seasonal variation of subgrade moisture content in the design process, a single value of Mr known as the “effective roadbed soil resilient modulus” is often used in design. A rational procedure for the determination of the seasonally adjusted resilient modulus is not described, although the seasonal variation of subgrade water content can be estimated with a reasonable level of confidence. A series of resilient modulus tests was designed to investigate the variation in Mr due to postcompaction increases in water content. Triplicate specimens were prepared for 11 soils throughout Tennessee, with each specimen prepared at target values of optimum water content and maximum dry density. One specimen was tested at optimum, and the other two were tested at increasing levels of saturation. All soils exhibited a decrease in resilient modulus with an increase in saturation, but the magnitude of the decrease in Mr was found to depend on the soil type. The soils with the highest Mr for optimum conditions were found to experience the greatest decrease with saturation. A method for correcting the resilient modulus for increasing degree of saturation is proposed. This method supports the procedure described by AASHTO, but an estimate of the monthly or seasonal variation in water content or degree of saturation is required.
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References
1.
American Association of State Highway and Transportation Officials (AASHTO). (1989). Standard specifications for transportation materials and methods of sampling and testing, Part II, methods of sampling and testing, Washington, D.C.
2.
American Association of State Highway and Transportation (AASHTO). (1992). “AASHTO interim method of test for resilient modulus of unbound granular base/subbase materials and subgrade soils—SHRP protocol P46.”Rep. AASHTO Designation T 294-92, Washington, D.C.
3.
American Association of State Highway and Transportation Officials (AASHTO). (1993). AASHTO guide for the design of pavement structures, Washington, D.C.
4.
Drumm, E. C., Boateng-Poku, Y., and Johnson Pierce, T.(1990). “Estimation of subgrade resilient modulus from standard tests.”J. Geotech. Engrg., ASCE, 116(5), 774–789.
5.
Drumm, E., Li, Z., Reeves, J. S., and Madgett, M. R.(1996). “Alternative test method for resilient modulus of fine-grained subgrades.”ASTM Geotech. Testing J., 19(2), 141–154.
6.
Drumm, E. C., Reeves, J. S., and Madgett, M. R. (1995). “Resilient response of Tennessee subgrades phase II: verification of prediction methods.”Rep. RES 1032 Prepared for the Tennessee Department of Transportation, Dept. of Civ. and Envir. Engrg., The Univ. of Tennessee, Knoxville, Tenn.
7.
Elfino, M. K., and Davidson, J. L. (1989). “Modeling field moisture in resilient moduli testing.”Resilient moduli of soils: laboratory conditions, ASCE, New York, N.Y., No. 24, 31–51.
8.
Elliot, R. P., and Thornton, S. I. (1988a). “Simplification of subgrade resilient modulus testing.”Transp. Res. Rec. 1192, 1–7.
9.
Elliot, R. P., and Thornton, S. I. (1988b). “Resilient modulus and AASHTO pavement design.”Transp. Res. Rec. 1196, 116–124.
10.
Holtz, R. D., and Kovacs, W. D. (1981). An introduction to geotechnical engineering. Prentice-Hall, Inc., Englewood Cliffs, N.J.
11.
Hudson, J., Drumm, E. C., and Madgett, M. (1994). “Design handbook for the estimation of resilient response of fine-grained subgrades.”Proc., 4th Int. Conf. on the Bearing Capacity of Roads and Airfields, Univ. of Minnesota, Minneapolis, Minn., 917–931.
12.
Johnson, T. D. (1986). “The resilient moduli of subgrade soil in the east Tennessee area,” MS thesis, Dept. of Civ. Engrg., The Univ. of Tennessee, Knoxville, Tenn.
13.
Lee, W., Bohra, N., and Altschaeffl, A. G.(1992). “Discussion of `Estimation of subgrade resilient modulus from standard tests,' by E. C. Drumm, Y. Boateng-Poku, and T. Johnson Pierce.”J. Geotech. Engrg., ASCE, 118(2), 352–354.
14.
Li, D., and Selig, E. T.(1994). “Resilient modulus for fine-grained subgrade soil.”J. Geotech. Engrg., ASCE, 120(6), 939–957.
15.
Madgett, M. R. (1994). “Verification testing and alternative test methods for the resilient modulus of fine grained soils,” MS thesis, Dept. of Civ. and Envir. Engrg., The Univ. of Tennessee, Knoxville, Tenn.
16.
Monismith, C. L. (1992). “Analytically-based asphalt pavement design and rehabilitation–theory to practice (1962–1992).”Proc., TRB Distinguished Lecture, Transp. Res. Board 71st Annu. Meeting, Transportation Research Board, Washington, D.C.
17.
Pezo, R., and Hudson, W. R.(1994). “Prediction models of resilient modulus for nongranular materials.”Geotech. Testing J., 17(3), 349–355.
18.
Pezo, R. F., Kim, D., Stokoe, K. H. II, and Hudson, W. R. (1991). “A reliable resilient modulus testing system.”Transp. Res. Rec. 1307, 90–98.
19.
Reeves, J. S. (1995). “Saturation effects on the resilient response of fine-grained soil,” MS thesis, Dept. of Civ. and Envir. Engrg., The Univ. of Tennessee, Knoxville, Tenn.
20.
SAS Institute Inc. (1990). Statistical analysis software, Cary, N.C.
21.
Seed, H. B., Chan, C. K., and Lee, C. E. (1962). “Resilience characteristics of subgrade soils and their relation to fatigue failures in asphalt pavements.”Proc., Int. Conf. on the Struct. Des. of Asphalt Pavements, Univ. of Michigan, Ann Arbor, Mich., 611–636.
22.
Strategic Highway Research Program (SHRP). (1989). “Resilient modulus of unbound granular base/subbase materials and subgrade soils.”Rep. Strategic Highway Research Program Protocol P-46, UG07, SS07, Washington, D.C.
23.
Tennessee Department of Transportation (TDOT). (1981). “Subgrade construction and preparation.”Specifications for road and bridge construction. Tennessee Department of Transportation Bureau of Highways, Kingsport, Tenn., Section 207.04.
24.
Thompson, M. R., and Elliot, R. P. (1985). “ILLI-PAVE-based response algorithms for design of conventional flexible pavements.”Transp. Res. Rec. 1043, 50–57.
25.
Thompson, M. R., and Robnett, Q. L. (1976). “Final report, resilient properties of subgrade soils.”Rep. Civ. Engrg. Studies Transp. Engrg. Ser. No. 14, Illinois Cooperative Hwy. and Transp. Ser. No. 160, Univ. of Illinois, Urbana-Champaign, Ill.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 123 • Issue 7 • July 1997
Pages: 663 - 670
Copyright
Copyright © 1997 American Society of Civil Engineers.
History
Published online: Jul 1, 1997
Published in print: Jul 1997
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