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LTPP Computed Parameter: Moisture ContentMarch 2008 FOREWORDThe ability to accurately monitor subsurface soil parameters on a continuous basis is extremely beneficial in pavement design, evaluation, and performance prediction. The time domain reflectometry (TDR) data collected as part of the Long Term Pavement Performance seasonal monitoring program (SMP) can be used to estimate moisture content, conductivity, reflectivity, and density. This report provides valuable information on calculating these parameters utilizing TDR traces and documents the process of interpreting over 270,000 TDR traces taken at SMP sites across North America. In situ data availability is critical to pavement engineering, particularly as the process moves toward mechanistic-empirical techniques. This study not only provides useful information from in-service pavements, but also provides a method that can be utilized by State highway agencies interested in monitoring subsurface conditions and analyzing their effect on pavement response. Gary Henderson Director, Office of Infrastructure Research and Development NoticeThis document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the information contained in this document. This report does not constitute a standard, specification, or regulation. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document. Quality Assurance StatementThe Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. TECHNICAL REPORT DOCUMENTATION PAGE
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized TABLE OF CONTENTSCHAPTER 2. BACKGROUND AND LITERATURE REVIEW
CHAPTER 4. COMPUTER PROGRAM DEVELOPMENT
CHAPTER 5. PARAMETER COMPUTATION AND QUALITY REVIEW
CHAPTER 6. LTPP DATABASE DELIVERY CHAPTER 8. RECOMMENDATIONS FOR FUTURE RESEARCH
CHAPTER 9. SUMMARY AND CONCLUSIONS APPENDIX A. TRANSMISSION LINE EQUATION
APPENDIX B. CHARACTERIZATION OF ERROR IN THE SID APPENDIX C. MICROMOIST USER'S MANUAL LIST OF FIGURESFigure 1. Diagram. TDR probe for SMP Figure 2. Graph. Typical TDR signal Figure 3. Diagram. Illustration of instrumentation installation Figure 4. Graph. Illustration of trace interpretation methods Figure 5. Flowchart. Volumetric moisture model selection process Figure 6. Diagram. Soil mixture with volume of soil solids equal to 1 Figure 7. Diagram. Coaxial line dimensions Figure 9. Bar Chart. Errors in volumetric moisture content estimates (calibration validation) Figure 10. Bar Chart. Errors of volumetric moisture contents on ground truth data Figure 11. Bar Chart. Errors of laboratory estimated dry density on ground truth data Figure 12. Bar Chart. Errors of volumetric moisture contents on ground truth data Figure 13. Bar Chart. Errors of estimated dry density on ground truth data (field validation) Figure 14. Photo. Interface of new program Figure 15. Graph. Inflection points in TDR trace Figure 16. Flowchart. Determination of inflection points Figure 17. Flowchart. Calculation of dielectric constant, conductivity, and reflectivity Figure 18. Flowchart. Calculation of moisture content and dry density Figure 19. Graph. TDR traces of Section 308129, TDR No. 8 Figure 20. Diagram. Three separate phases of a soil element Figure 21. Diagram. Profile of TDR and depth at each layer Figure 22. Graph. Uninterpretable TDR trace Figure 23. Graph. Incomplete TDR trace Figure 24. Graph. Shift zone in LTPP section 091803, TDR sensor No. 7 Figure 25. Graph. Soil-water characteristic curve for sandy soil Figure 26. Diagram. Diagrams of soil having different volume Figure 27. Graph. Comparison of SWCC and VMC-DC trend Figure 28. Graph. Sample plot of moisture content seasonal trend Figure 29. Graph. Results from the apparent length approach for LTPP section 063042 Figure 30. Graph. Results from the TLE micromechanics method for LTPP section 063042 Figure 31. Graph. Results from the apparent length approach for LTPP section 313018 Figure 32. Graph. Results from the TLE micromechanics method for LTPP section 313018 Figure 33. Graph. Time-harmonic function V(t) Figure 34. Graph. Electric field as a function of z direction at different times Figure 35. Diagram. Coaxial line Figure 36. Graph. Cylindrical coordinate system Figure 37. Diagram. Coaxial line developed into a parallel-plate waveguide LIST OF TABLESTable 1. Instrumentation for SMP Table 2. SMP core experiment sectioning category Table 3. Coefficient for mixing model Table 4. Third order polynomial Ka-soil model parameters Table 5. Refined third order polynomial Ka-soil model parameters Table 6. Comparison of volumetric moisture contents during TDR installation Table 7. Calibrated and calculated values determined by micromechanics method Table 8. Calibration of dielectric constants by transmission line equation Table 9. Comparison of moisture contents Table 10. Calibration of dielectric constants for Section 091803 Table 11. Comparison of moisture contents for Section 091803 Table 12. Overview of LTPP MicroMoist program Table 13. Dry density adjustment of Section 331001 and 533813 Table 14. Calibrated values of Section 331001 and 533813 Table 15. Field names and description of MICROMOIST_SMP_TDR_AUTO table Table 16. Field names and description of MICROMOIST_SMP_TDR_DEPTHS_LENGTH table Table 17. Field names and description of MICROMOIST_SMP_TDR_CALIBRATE table Table 18. Field names and description of MICROMOIST_SMP_TDR_AUTO_DIELECTRIC table Table 19. Field names and description of MICROMOIST_SMP_TDR_AUTO_MOISTURE table Table 20. Error codes used in the program Table 21. Description of SMP_TDR_CALIBRATE table for the LTPP IMS Database Table 22. Description of SMP_TDR_MOISTURE table for the LTPP IMS Database LIST OF ACRONYMS AND ABBREVIATIONS
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This page last modified on 04/15/08 |