Subgrade characterization for highway pavement design.

Details

• Creators:
  George, K. P. ; Uddin, Waheed
• Corporate Creators:
  University of Mississippi. Dept. of Civil Engineering
• Corporate Contributors:
  Mississippi. Dept. of Transportation. Research Division
• Subject/TRT Terms:
  • Subgrade (Pavements)
  • Modulus of resilience
  • Mechanistic design
  • Pavement design
  • Cone penetrometers
  • Falling weight deflectometers
  • Correlation analysis
  • Subgrade
  • Soil characterization
  • Resilient modulus,
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• Publication/ Report Number:
  FHWA/MS-DOT-RD-00-131
• Resource Type:
  Tech Report
• Geographical Coverage:
  Mississippi
• Edition:
  Final; Jan. 26, 1999-Dec. 31, 2000.
• Corporate Publisher:
  Mississippi. Dept. of Transportation
• Abstract:
  Subgrade soil characterization expressed in terms of Resilient Modulus (MR) has become crucial for pavement design. For a new design, MR ; values are generally obtained by conducting repeated triaxial tests on reconstituted/undisturbed cylindrical specimens. Because of the ; complexities encountered with the test, in-situ tests would be desirable, if reliable correlation can be established. In evaluating existing ; pavements for rehabilitation selection, subgrade characterization is even more complex. The main focus of this study is to determine subgrade ; MR employing a Dynamic Cone Penetrometer (DCP), especially the automated version. In support of the study, side-by-side Falling Weight ; Deflectometer tests are also conducted. ; Twelve as-built test sections reflecting typical subgrade soil materials of Mississippi are selected and tested with DCP and FWD before and after ; pavement construction. Undisturbed samples are extracted using a Shelby tube, and tested in repeated triaxial machine for MR. Other routine ; laboratory tests are conducted to determine physical properties of the soil. In analyzing the data, the soils tested are categorized into two groups, ; fine-and coarse-grain soils. ; DCP results (DCP index, penetration/blow) from tests conducted directly in the prepared subgrade are employed to develop regression models ; for laboratory MR prediction. The predictability of the model is substantiated by repeating DCP tests at an independent site. Models for in-situ ; modulus prediction are also developed in the study. Deflection measurements facilitated the calculation of in-situ modulus, for which three ; programs were used: MODULUS 5, FWDSOIL and UMPED. The MODULUS 5 –backcalculated subgrade modulus shows good agreement ; with the laboratory MR. The FWDSOIL backcalculation program predicts subgrade moduli which are slightly lower than the laboratory MR. ; With emplacement of pavement structure (lime treated subgrade, lime fly ash subbase, and several inches of asphalt concrete) atop the subgrade, ; the subgrade backcalculated moduli are enhanced, coarse-grain soil showing a larger increase than the fine-grain soil. This latter result, namely ; the enhancement of subgrade moduli, is substantiated employing the data compiled from 20 LTPP pavement sections in Mississippi. In order to ; analyze the automated DCP results, a software designated Dynamic Cone Penetrometer ANaylsis (DCPAN), has been developed. With the ; regression equation incorporated in the software, real time laboratory as well as backcalculated subgrade modulus calculations are plausible in ; the field.
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• Format:
  PDF
• Funding:
  State Study 131
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24131/dot_24131_DS1.pdf
• File Type:
  [PDF - 3.70 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:5660e6bd650f50c07fcf55b36184558641d8139ae3cde884a89b9a72de60ec9c566d6ee5bbd6215163e10e54e8f3ea010cf252b0201bb00441afab33400b4874