Performance of Drained and Undrained Flexible Pavements in Long-Term Pavement Performance SPS-1 Experiment

Drainage is the experimental factor about which conclusions from the SPS-1 experiments are most difficult to draw. This is because two experimental factors, base type and subdrainage, are confounded in the experiment. This paper describes the findings from NCHRP Project 1-34D, in which data from the LTPP SPS-1 (flexible) pavement design experiment were used to assess whether pavements with subsurface drainage systems (permeable base, collectors, and outlets) performed differently from pavements without subsurface drainage systems. The data analyzed included IRI, rutting, cracking, and deflection data from the LTPP database, as well as drainage system flow time measurements obtained from field testing. Long-term IRI values for the SPS-1 flexible pavements were found to be more strongly correlated to initial IRI values than to all of the SPS-1 experimental factors combined. The next most influential factors were found to be age, backcalculated equivalent thickness of the pavement structure, Thornthwaite moisture index, and average annual precipitation. The base type/drainage factors showed very little correlation to long-term IRI values. Rutting levels were similar for all of the base type/drainage combinations, except that the undrained aggregate base group had a higher percentage of sections with unusually high rutting at an early age. Base stiffness, rather than drainage, is concluded to be the aspect of the base type/drainage experimental factor that is responsible for whatever role this factor has played in the development of rutting in the SPS-1 test sections. About half of the SPS-1 test sections in each base type/drainage group have not yet developed any cracking. Among those that have, the weaker pavement sections (undrained AGG base and drained PATB) have more cracking than the stronger pavement sections (undrained ATB, undrained ATB over aggregate, and drained ATB over PATB). Whatever minor effect the base type/drainage factor has had on cracking in the SPS-1 pavement sections to date is concluded to be due to differences in base stiffness rather than differences in drainage.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: References; Tables;
  • Pagination: 21p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

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Filing Info

  • Accession Number: 01043887
  • Record Type: Publication
  • Report/Paper Numbers: 07-2871
  • Files: PRP, TRIS, TRB
  • Created Date: Feb 8 2007 7:34PM