LTPP Computed Parameter: Moisture Content

Appendix C. MicroMoist User's manual

The user's manual documents and describes the various features of the MicroMoist program. This will serve as a tool in the installation, navigation, and data processing components of the program. The program was developed to automate, to the extent practical, procedures in interpreting time domain reflectometry (TDR) traces to estimate soil parameters such as moisture content and dry density. MicroMoist was developed specifically for use on data stored in the LTPP database. The program requires input tables to be in a specified format. Other data can be analyzed in with MicroMoist as long as the input data are structured in accordance with this manual.

This manual is divided into three main sections:

• Introduction to the Program
• Getting Started in the Program
• Program Features

Introduction to the Program

In 1992, the Seasonal Monitoring Program (SMP) was initiated within the LTPP study in order to understand the environmental factors and the relationship with pavement performance. Sixty-four LTPP test sections were selected for the SMP according to pavement type, thickness, environment, and subgrade type. Several instruments were installed at each section to acquire data on in situ moisture content and temperature of sublayers, frost penetration, and depth to ground water. As part of this program, TDR technology was selected to measure in situ moisture content of pavement sublayers. TDR data were collected with 8-inch TDR probes developed by FHWA. Ten TDR probes were installed for each SMP test section at specified depths in the unbound base and subgrade layers below the outer wheel path.

This program was developed based on the approach of using transmission line equations (TLE) and micromechanic models to estimate soil parameters from TDR traces. In this approach, the TLE is used to solve for the dielectric constant of the soil. The dielectric value was then employed in a micromechanics model calibrated specifically to each site and layer combination to determine soil parameters. MicroMoist allows users to view and process TDR traces based on this approach.

MicroMoist extracts data from three input tables that are in Microsoft Access format and shows the smoothed trace on the screen. The trace shown on the screen is processed automatically using the algorithm implemented by the program, which identifies the inflection points and displays the points on the trace. The soil dielectric constant is determined using the data points on the TDR trace between the inflection points.

The program can process TDR traces in the following ways:

• MicroMoist automatically processes all the TDR traces collectively and shows the identified inflection points on the screen for review.
• For QC purposes, users can view all traces and have the option of adjusting the location of the inflection points. Changed inflection points automatically get recorded as new points on the trace and are hence used for the calculation.

The resultant soil parameters and supporting computations are provided in two Access database tables.

The program was designed with features that make it an efficient tool for reviewing TDR traces and computing parameters of interest.

Getting Started in the Program

Getting started with the new program is easy, especially if Windows XP operating system is currently installed on the target workstation.

System Requirements

To run MicroMoist, the following minimum hardware and software requirements must be met:

• IBM-compatible Pentium processor
• 512 MB of RAM (1 GB recommended)
• 1 MB of available hard disk space, depending on the size of the TDR trace table
• Super video graphics adapter with at least 800*600 resolution and 256 colors
• Microsoft mouse or compatible pointing device
• Microsoft Windows XP operating system.

Installing and Running the Program

The MicroMoist program is an executable file which does not need to be installed. The program can be run once the program files are copied to the appropriate drive.

Program Features

MicroMoist was developed to allow users to view TDR traces as well as to automate the process of estimating soil parameters from the traces. In light of this, the following functions and features were incorporated into the program. MicroMoist is a powerful tool for the analysis of TDR traces; however, users must be familiar with TDR data collection principles, equipment, and techniques.

Raw TDR Trace Data

The program extracts raw TDR trace data points from an Access database into an Access table. This table should be the same format and structure as the SMP_TDR_AUTO table in the LTPP database. The table contains a flat representation of the TDR waveform sampled at 245 intervals and stored in the WAVEP_1 through WAVP_245 field. The table to be queried by MicroMoist can have any name. A sample table is provided with the program. This table must be provided with the following two tables (SMP_TDR_DEPTHS_LENTH and SMP_TDR_CALIBRATE) together in one Access database prior to running the program.

TDR Depth Records

The MicroMoist program also requires the SMP_TDR_DEPTHS_LENGTH table in the Access database to extract information on installation depths of TDR sensors. This table needs to be the same structure and format as the SMP_TDR_DEPTHS_LENGTH table in the LTPP database, which contains the physical information of the TDR probes such as the depths at which the probes are installed, their installation date, and the length of TDR probes. This table is used to link to SMP_TDR_AUTO to determine the depth corresponding to a TDR trace, using the STATE_CODE, SHRP_ID, TDR_NO, and CONSTRUCTION_NO. A sample table is provided with the program. This table must be provided with the raw TDR trace table and the following table (i.e., SMP_TDR_CALIBRATE) in one Access database prior to running the program.

TDR Calibration Records

MicroMoist also utilizes calibration information for each site and TDR sensor. A table named SMP_TDR_CALIBRATE is required in the Access database. The SMP_TDR_CALIBRATE table contains the calibrated dielectric constants of soil components and specific gravity. The calibrated values are required to calculate moisture content and dry density values by linking SMP_TDR_CALIBRATE by STATE_CODE, SHRP_ID, and TDR_NO fields. A sample table is provided with the program. This table must be provided with the raw TDR trace table and the SMP_TDR_DEPTHS_LENGTH table in an Access database prior to running the program.

Starting the Program

When MicroMoist is started, the main TDR data processing window appears. The user must first open an Access database containing the raw TDR trace table as described in "Raw TDR Trace Data."

TDR Program Menus

Menus in MicroMoist are context sensitive; both the available menus and their contexts change according to which part of the program is active. Menu features are briefly discussed in this section.

The toolbar buttons provide shortcuts to all the menu items. The menu items and corresponding toolbar buttons are both described below.

Menu bar:

• OPEN: Opens dialog box to select the database for processing.
• EXIT: Ends the program, closing all the connections and the database.

Toolbar: Contains icons in the order listed below:

• OPEN: Open dialog box to select the database for processing.
• CLOSE: Ends the program, closing all the connections and the database.
• Previous Trace: View previous TDR trace in database.
• Go To: View a specific TDR trace based on location in the database.
• Next Trace: View next TDR trace in database.
• Show Trace: Refresh current TDR trace.
• Change Inflection Points: Manually select inflection points on TDR trace.
• Write Dielectric Output: Compute dielectric constant of TDR trace and store in database.
• Write Moisture Output: Compute moisture content and store in database.

The screen contains a combo box, labeled "Dubious Records," which lists TDR traces that do not pass criteria checks. Traces with positive slope or wrong inflection points fall into this category. Additional information is also provided on the screen, including SHRP_ID, STATE CODE, CONSTRUCION NUMBER, SMP DATE, TDR TIME, and TDR NUMBER, DIST_WAV of the TDR trace currently displayed.

Output Table after Running Program

Utilizing data from the input database tables described above, the program generates two output tables: SMP_TDR_AUTO_DIELECTRIC and SMP_TDR_ MOISTURE. These tables are automatically generated in the Access database containing the input data tables.

The SMP_TDR_AUTO_DIELECTRIC table contains dielectric constant, conductivity, and reflectivity values computed from interpretable TDR records in SMP_TDR_AUTO. This table is generated by running the Write Dielectric Output option on the toolbar.

The SMP_TDR_ MOISTURE table contains the dry density, volumetric moisture content, and gravimetric moisture content values computed from interpretable TDR traces in the SMP_TDR_AUTO table and is generated by running the Write Moisture Output option on the toolbar.