Long-Term Pavement Performance Computed Parameter: Frost Penetration

CHAPTER 6. LTPP DATA USED FOR FROST DETERMINATION

During Phase I of the project, the research team assessed the availability of the LTPP data needed to support the enhanced algorithm for evaluation of frost penetration. This assessment included data utilized by the existing FROST procedure and the LTPP data that will be utilized by the enhanced FROST procedure. The results of the assessment are summarized in this section.

DATA REQUIRED FOR E-FROST ANALYSIS

The following LTPP database tables containing subsurface temperature, electrical resistivity, and moisture data were used to determine frost penetration under bound pavement layers:

• SMP_ERESIST_AUTO_ABF—Contains new ER measurements (VOLTAGE and RESISTANCE) for SMP II sections.
• SMP_ERESIST_AUTO—Contains automated electrical contact voltage data for each electrode number.
• SMP_ERESIST_MAN_4POINT—Contains manually collected four point electrical contact resistance measurements:
  • Voltage reading between voltage electrodes.
  • Electrical current reading between current electrodes.
  • Computed electrical resistivity.
• SMP_ERESIST_MAN_CONTACT—Contains manually collected two point electrical contact resistance measurements:
  • Voltage reading between electrodes.
  • Electrical current reading between electrodes.
  • Computed contact resistance between two electrodes.
• SMP_ERESIST_DEPTHS—Contains depth from the pavement surface for each electrode.
• SMP_MRCTEMP_AUTO_DAY_STATS—Contains daily pavement subsurface temperature for the thermistors in the MRC thermistor probe closest to the surface.
• SMP_MRCTEMP_DEPTHS—Contains the installed thermistor depth.
• SMP_ERESIST_ABF_REF_VA—Contains background information related to ER measurements using ABF equipment for SMP II sections (this table is not be used directly in the ER data processing).
• SMP_TDR_AUTO_MOISTURE—Contains computed volumetric moisture content in percentile form.
• SMP_TDR_MANUAL_MOISTURE—Contains volumetric moisture content in percentile form based on most probable value of apparent length interpreted from manual TDR trace.
• SMP_TDR_DEPTHS_LENGTH TDR_DEPTH— Contains depth from pavement surface to TDR probe in meters.

Data from 1993 to 2001 were used to reinterpret previous frost estimates, and data from 2001 to 2004 were used to develop new frost estimates.

DATA REQUIRED FOR EICM ANALYSIS

In applying the EICM, the project team used section-specific data where they were available and pertinent to subsurface temperature prediction. The actual climatic measurements, layer, and material information collected at the site were used as inputs to the EICM. These measurements are included in the following tables:

• INV_ID—Contains longitude, latitude and elevation information.
• INV_GRADATION—Contains information about particle sizes.
• TST_L05B— Contains information about number of layers, layer and material type and layer thickness.
• TST_UG04_SS03—Contains information about plasticity index.
• TST_SS11—Contains hydraulic conductivity and initial water content information.
• TST_UG09—Contains hydraulic conductivity information.
• SMP_ATEMP_RAIN_DAY—Contains daily air temperature and rainfall statistics.
• SMP_ATEMP_RAIN_HOUR—Contains hourly ambient air temperature and rainfall.
• SMP_DRY_DENSITY—Contains subgrade dry density measurements.
• SMP_ELEV_AC_DATA—Contains AC surface elevation measurements.
• SMP_ELEV_PCC_DATA—Contains PCC surface elevation measurements.
• SMP_GRAV_MOIST—Contains pavement subsurface gravimetric moisture content.
• SMP_MRCTEMP_AUTO_DAY_STATS—Contains daily pavement subsurface temperature statistics.
• SMP_WATERTAB_DEPTH_MAN—Contains automated data on the depth to ground water table.
• CLM_VWS_TEMP_DAILY—Contains daily temperature data.
• CLM_VWS_WIND_DAILY—Contains daily wind data.
• AWS_DAILY_DATA—Contains daily temperature and wind data.

Default or assumed values were used for some of the required data elements that were not included in the LTPP database. The climatic data from the National Climatic Data Center for a specified longitude and latitude were used where section-specific weather data were not available. These climatic data are integrated in the EICM program. EICM inputs are provided in appendix B.

ANALYSIS DATABASE SUMMARY

The data from the LTPP tables discussed above were assembled in the analysis database. All records were organized by LTPP site, date, and measurement depth. For each analysis site and date, up to 35 records containing ER, temperature, and moisture data were prepared—one for each analysis depth.

One of the issues in processing electrical resistivity, moisture, and soil temperature data was that these data elements are measured at different depths. Therefore, data manipulation was required to correlate various electrical resistivity, soil temperature, and moisture values. To preserve the same interpretation depths as were used in the previous LTPP frost studies,⁽³⁾ linear interpolation was used to obtain soil temperature and moisture values at the ER interpretation depth. In the previous LTPP frost studies, ER interpretation depth was defined as a middepth between two neighboring electrodes, resulting in 35 analysis depths for 36 electrodes included in the resistivity probe.

Only dates that had either ER or temperature data were included in the analysis database. Records for the months with the minimum monthly temperature above +1 °C and with no ER data were not included in the analysis database because no freeze conditions are possible when temperatures are above +1 °C.

EICM-predicted temperatures were added to the database to fill in the gaps in measured temperature data. EICM predictions were provided only for the sites that had sufficient site-specific EICM inputs. Only gaps of less than one month were filled with EICM predicted temperature values. Source of temperature data was specified in the analysis database to differentiate between measured and predicted temperature data.

Table 5 summarizes the number of records that were assembled in the analysis database for each of the 41 LTPP SMP sites included in the frost study. As can be seen, measured temperature data were the most complete data element, corresponding to the largest number of records in the analysis database.

Events

• View all Upcoming Pavements Events

More Information

• Pavement Publications

Contact

Customer Service
202-493-3035
E-mail Customer