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Publication Number: FHWA-HRT-08-035
Date: March 2008

LTPP Computed Parameter: Moisture Content

Chapter 6. LTPP Database Delivery

This chapter provides details on the data delivered for upload into the LTPP IMS database. Two tables were developed specifically to store data from this study: SMP_TDR_CALIBRATE and SMP_TDR_MOISTURE.

Table 21. Description of SMP_TDR_CALIBRATE table for the LTPP IMS Database.
Field Comment
STATE_CODE Numerical code for State or Province.
SHRP_ID Test section identification number assigned by LTPP.
TDR_NO TDR sensor number.
CAL_DRY_DENSITY Retrieved from other LTPP tables or assumed.
SOURCE_DRY_DENSITY_TDR Code indicating source of CAL_DRY_DENSITY. 1-SMP installation report 2-SMP installation report - I07 form 3-SMP installation report - S04 form 4-SMP installation report - I05 form 5-IMS table TST_ISD_MOIST 6-IMS table TST_SS08 7-IMS table INV_SUBGRADE 8-From Appendix C of "Analysis of Time Domain Reflectometry Data From LTPP Seasonal Monitoring Program Test Sections-Final Report" FHWA-RD-99-115
CAL_DRY_DENSITY_ADJUSTMENT_METHOD Code indicating type of adjustment made to CAL_DRY_DENSITY. 1-Adjustment based on vertical variation 2-Adjustment based on vertical variation and air volume
CAL_VOLUMETRIC_MOISTURE_CONTENT Measured VMC from samples taken during installation.
CAL_SOIL_DIELECTRIC Dielectric constant estimated from manual TDR trace taken at installation (from SMP Installation Report).
CAL_DIELECTRIC_SOLIDS Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations.
CAL_DIELECTRIC_WATER Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations.
CAL_DIELECTRIC_AIR Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations.
CAL_SPECIFIC_GRAVITY Computed using dry density and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent density computations.

The SMP_TDR_MOISTURE table contains dielectric constant, moisture, conductivity, and reflectivity data estimated from automated TDR traces. A description of each field can be found in table 22.

Table 22. Description of SMP_TDR_MOISTURE table for the LTPP IMS Database.
Field Comment
STATE_CODE Numerical code for State or Province.
SHRP_ID Test section identification number assigned by LTPP.
SMP_DATE Date TDR trace was obtained.
TDR_TIME Time TDR trace was obtained.
TDR_NO TDR sensor number.
TLE_BEGIN Starting point of interval on TDR trace captured for use in the Transmission Line Equation.
TLE_END Ending point of interval on TDR trace captured for use in the Transmission Line Equation.
SOIL_DIELECTRIC Dielectric constant estimated from TDR trace (from SMP_TDR_AUTO).
SOIL_CONDUCTIVITY Conductivity estimated from TDR trace (from SMP_TDR_AUTO).
SOIL_REFLECTIVITY Reflectivity estimated from TDR trace (from SMP_TDR_AUTO).
DRY_DENSITY Dry density estimated from SOIL_DIELECTRIC and calibrated micromechanics equation.
VOLUMETRIC_MOISTURE_CONTENT VMC estimated from SOIL_DIELECTRIC and calibrated micromechanics equation.
GRAVIMETRIC_MOISTURE_CONTENT GMC estimated from VMC and DRY_DENSITY.
TDR_COMPUTATION_COMMENT_CODE Codes to describe traces that could not be interpreted. 1-TDR trace uninterpretable due to lack of negative slope 2-Questionable data due to low dry density value 3-Calibration data from installation activities are unavailable 4-Outlier data based on time series analysis 5-Volumetric moisture content was in transition zone and was adjusted

 

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