DETERMINATION OF DEPTH TO BEDROCK FROM FALLING WEIGHT DEFLECTOMETER TEST DATA

Depth to bedrock can have a significant effect on the moduli of the surface layer, base, and subgrade backcalculated from Falling Weight Deflectometer (FWD) tests when the calculations are performed using a static analysis. On the other hand, when the backcalculation is based on dynamic analysis of the FWD test, the resulting moduli are quite insensitive to the depth to bedrock if this depth is larger than about 3 m (10 ft). When only the peak deflections at the seven receivers are recorded, there is little that can be done analytically to account for the depth to bedrock. However, when the time histories of the motions at the various receivers are stored, one can estimate both the depth to bedrock and the modulus of the subgrade rather easily from the time histories. These estimations are most correctly applied to time histories of 0.12 sec or longer rather than the 0.06 sec conventionally recorded. In this article, the results of a number of parametric studies simulating the FWD test on three flexible pavements and one rigid pavement are presented. From these results, approximate expressions were developed for (a) estimating the depth to bedrock, (b) computing the natural period of vibration of the pavement system, which is nearly equal to that of the subgrade layer, and (c) estimating the wave propagation velocity and modulus.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 68-78
  • Monograph Title: Modeling and model verification; testing pavement layers and materials; and low-cost drainage structures
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00715544
  • Record Type: Publication
  • ISBN: 0309061725
  • Files: TRIS, TRB
  • Created Date: Jan 2 1996 12:00AM