United States Department of Transportation
i
Long term pavement performance computed parameter : moisture content
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2008-01-01
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[PDF-870.71 KB]
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OCLC Number:259716835
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Edition:Final report Jul 2005 to Sep 2007
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION;NTL-HIGHWAY/ROAD TRANSPORTATION-Materials;NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance;NTL-REFERENCES AND DIRECTORIES-Statistics;
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Abstract:A study was conducted to compute in situ soil parameters based on time domain reflectometry (TDR) traces obtained
from Long Term Pavement Performance (LTPP) test sections instrumented for the seasonal monitoring program (SMP).
Ten TDR sensors were installed in the base and subgrade layers at each of the 70 SMP test sites monitored as part of the
LTPP program. A comprehensive description of a new method developed as part of the study to estimate moisture
content, dry density, reflectivity, and conductivity of the soil from TDR traces is provided in the report. This new
method utilizes transmission line equations and micromechanics models calibrated to site-specific conditions for each
site/layer combination. Background information on existing empirical methodologies used to estimate subsurface
moisture content from TDR traces is also documented. The results were compared to previous methods as well as
ground truth data to evaluate the ability of the new model to predict soil parameters. The transmission line equation and
micromechanics method was found to provide accurate results and was used to interpret over 270,000 TDR records
stored in the LTPP database. A computer program (MicroMoist) was developed to aid in the computation of soil
parameters based on TDR trace data and calibration information. Details on the program are provided along with
descriptions of the tables developed to store the computed values in the LTPP Information Management System
database.
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