In Situ Modulus Measurement Using Automated Plate Load Testing (APLT)
Project Name: In Situ Modulus Measurement Using Automated Plate Load Testing (APLT) for Statewide Mechanistic-Empirical Design Calibration
Project Date: 10/12/2017 to 5/29/2018
Location: Iowa (Sac, Story, Jasper, Linn, Woodbury, Polk Counties)
Partners: Iowa Department of Transportation
Public Agencies (Pavement System Owners): FHWA, State DOTs, Tollway Authorities
Ingios Engineers Involved: David J. White, Pavana Vennapusa, E. Tom Cackler, Heath Gieselman, Colby Van Nimwegen
White, D.J., Vennapusa, P., Cackler, E.T. (2019). “In Situ Modulus Measurement Using Automated Plate Load Testing for State Wide Mechanistic-Empirical Design Calibration,” Final Report ST-003, Iowa Highway Research Board, Ames, Iowa. Microsoft Word - Iowa STIC Project Report_v12
Challenge: The Iowa DOT needed a reliable method to determine pavement foundation related design input parameters for calibration of the new AASHTOWare Pavement ME Design™ software. The ME calibration process for foundation input parameters is primarily empirical or relies upon limited and often time-consuming laboratory testing and adopting conservative values. Even with modern laboratory testing of foundation materials, various challenges limit the understanding of in situ conditions.
Solution: Ingios Geotechnics addressed the Iowa DOT’s challenges by providing direct measurement of design input parameters using the Automated Plate Load Test (APLT).
10 project sites were selected that covered unbound foundation layer cross-sections used in Iowa highways. The goal at each site was to perform cyclic APLTs to determine stress-dependent composite and layered resilient modulus (Mr) (modified AASHTO T 221 and T 307) and perform static APLTs to determine modulus of subgrade reaction (k-value) (AASHTO T 222). Results measured from each site were compared with the design input parameters for each project.
Benefits: Results revealed significant variability in the pavement foundation support conditions with sometimes the values being under-conservative and sometimes being over-conservative. Based on the results, the Iowa DOT realized the opportunity to significantly improve construction quality through changes in QC/QA specifications and direct verification testing, and thereby improve pavement performance and reducing future pavement maintenance.