Falling weight deflectometer for estimating subgrade resilient moduli.

Details

• Creators:
  George, K. P.
• Corporate Creators:
  University of Mississippi. Dept. of Civil Engineering
• Corporate Contributors:
  Mississippi. Dept. of Transportation. Research Division
• Subject/TRT Terms:
  • Nondestructive tests
  • Subgrade (Pavements)
  • Falling weight deflectometers
  • Modulus of resilience
  • Correlation analysis
  • Pavements--Subgrades--Testing
  • Non-destructive testing
• Publication/ Report Number:
  FHWA/MS-DOT-RD-03-153 ; MS-DOT-RD-03-153
• Resource Type:
  Tech Report
• Geographical Coverage:
  Mississippi
• Edition:
  Final report; Jan. 2002-Dec. 2003.
• Corporate Publisher:
  University of Mississippi
• Abstract:
  Subgrade soil characterization expressed in terms of resilient modulus, MR, has become crucial for pavement design. For ; new pavement design, MR values are generally obtained by conducting repeated load triaxial tests on reconstituted/undisturbed ; cylindrical specimens, employing TP46 protocol. 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 focus of this study is to investigate the viability of Falling Weight Deflectometer (FWD) ; for direct testing of subgrade with the object of deriving resilient modulus, via a correlation between FWD modulus and MR. In ; support of this research, side-by-side Automated Dynamic Cone Penetrometer (ADCP) tests were also conducted. ; Ten as-built subgrade sections reflecting typical subgrade soil materials of Mississippi were selected and tested with FWD. ; Both fine- and coarse-grain soils were included in the program. Undisturbed samples were extracted using a Shelby tube and tested in ; a repeated load triaxial machine for MR, employing TP46 protocol. Other routine laboratory tests are conducted to determine physical ; properties, and, in turn, classify the soil being tested. ; Employing seven FWD sensor deflections, elastic moduli, E1 to E7, are calculated employing forward equations (assuming ; static half-space). E1 and E3-5 (average of E3, E4, and E5) are regressed against MR, advancing two models for MR prediction. ; Employing E1 and E3-5, two distinct resilient moduli are derived, with the lesser of the two serving as the design resilient modulus. A ; feature of the model is that both center sensor modulus and offset sensor moduli enter in the process, yielding a representative, but ; conservative, resilient modulus for design. Having been derived from multiple sensor moduli, this procedure promises to be a viable ; method for subgrade characterization, considering significant nonhomogenity expected of built-up subgrades. Also suggested is a ; short-cut procedure for predicting resilient modulus which employs an E3-5 section average for a low moduli range, that is, E1<9000 ; psi (62 MPa), and lesser of E1 and E3-5 for E1>9000 psi (62 MPa). ; An exclusive program, FWDSUBGRADE, is developed to analyze FWD deflection data from subgrade tests, extracting first ; sensor modulus E1, and average of three offset sensor moduli, E3-5, from which only design resilient modulus is derived. The ; program, in addition to calculating station-by-station resilient modulus, relying on what is known as “cumulative difference” ; technique, delineates homogenous units of the subgrade, outputting mean and standard deviation of the resilient modulus for each ; homogenous section. A graphical plot of resilient modulus of each station is another output of the program.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24145/dot_24145_DS1.pdf
• File Type:
  [PDF - 1.02 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:75d8c1338991b8b227eb654855a9e13dd2f1b3963e63515e3289cdce50d82b5743242bb12a7e51e72e0331497f44140d3d0d529ad8edfd496c577f61d96b6541