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INTEGRATING A NATIONAL DATABASE OF SUBGRADE SOIL-WATER CHARACTERISTIC CURVES AND SOIL INDEX PROPERTIES WITH THE M-EPDG Claudia Zapata, Ph.D. * Assistant Professor Department of Civil, Sustainable and Environmental Engineering Arizona State University P.O. Box 875306, Tempe, AZ 85287-5306 E-mail:
[email protected] and Carlos E. Cary, Ph.D. Research Associate Department of Civil, Environmental and Sustainable Engineering Arizona State University PO Box 875306, Tempe, AZ 85287-5306 E-mail:
[email protected] *Corresponding author Submitted for Presentation and Publication in the 92nd Annual Meeting of the Transportation Research Board Submit date: August 1st, 2012 Word Count: 5,236 Number of Tables: 0 Number of Figures: 7 = 1,750 Total Word Count: 6,986
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ABSTRACT The database developed under the NCHRP 9-23A project, entitled "Development of a National Catalog of Subgrade Soil-Water Characteristic Curves (SWCC) Default Inputs to Use in the Mechanistic Empirical Pavement Design Guide (M-EPDG)", included not only measured soil index properties needed in all hierarchical levels of the Enhanced Integrated Climatic Model (EICM) but also soil-water characteristic curve (SWCC) parameters, which are key in the implementation of Level 1 analyses. A set of maps in portable document format (pdf) displaying the location of every soil unit identified within the continental US, Hawaii, Alaska and Puerto Rico; and a simple interface in Excel to aid in the query of data were also developed for the project. Under NCHRP 9-23B project, entitled "Integrating the National Database of Subgrade Soil-Water Characteristic Curves and Soil Index Properties with the M-EPDG", a second research effort was directed to integrate an enhanced version of the GIS-enabled database with the M-EPDG. Specifically, NCHRP 9-23B project aimed at the implementation of an interactive tool that allows the M-EPDG (current DarWin-ME) users to retrieve both appropriate soil unit maps and soil properties relevant to a particular user-specified location by inputting either state milepost information or geographical coordinates. The final product was integrated into a public website that can be accessed by the guide users, agencies, industry and academicians through a simple link. This document presents details of the development of this useful search tool and outlines its main features.
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INTRODUCTION Within the M-EPDG (and its successor program, AASHTOWare’s DARWin-ME), the EICM handles input collection, characterization, and analysis of the effects of environmental factors and material properties on the stiffness of unbound materials. The output of the EICM has a significant impact on the final distress predictions provided by the M-EPDG. The EICM requires several types of input parameters in order to accurately predict the environmental adjustment factors; these can be divided into two main categories: climatic information and material properties for unbound (granular base and subbase) and subgrade materials. The climatic information is readily available to the user of the MEPDG through the internal provision of datasets for more than 800 U.S. weather stations with hourly information that includes precipitation, temperature, wind speed, cloud cover and relative humidity. By contrast, the required unbound material information ranges from routine soil index properties to a specialized set of moisture retention parameters (soil-water characteristic curve parameters) that are fundamental to the consideration of moisture prediction and soil stiffness of all unbound layers. The soil index properties include parameters such as grain-size distribution, Atterberg limits, porosity, and saturated hydraulic conductivity, which are well-known to both practitioners and researchers in the pavement engineering community. However, the soil-water retention parameters are relatively unfamiliar to this community, despite the fact that they are widely used in the agricultural sciences and play a key role in defining the stress state of unsaturated soils. In NCHRP Project 9-23A "Development of a National Catalog of Subgrade Soil-Water Characteristic Curves (SWCC) Default Inputs to Use in the M-EPDG," Arizona State University developed a national database of M-EPDG input properties for subgrade materials. The database includes SWCC parameters, which are key parameters in the implementation of the M-EPDG Level 1 pavement design analysis, as well as measured soil index properties needed by the EICM at all levels of analyses. In addition, the project developed a simple user's interface to facilitate the search for a particular soil profile when the location of the project is known. The interface was developed using Microsoft Excel® and Adobe Acrobat®. Project location maps were provided in Adobe portable document format (pdf) files, while Excel was used for the soils database and coding of the user interface. To further encourage the use of the maps and database developed in NCHRP Project 923A, an interactive search tool based on Google Maps and capable of displaying soil unit maps and generating reports was conceived and produced as part of NCHRP Project 9-23B. The importance of this tool is that it is designed for easy linking to the M-EPDG software and can be used by any practitioner interested in obtaining preliminary site condition information needed for the design and analysis of new and rehabilitated pavement structures.
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OBJECTIVE The specific objective of this research was to facilitate the integration of an enhanced version of the GIS-enabled national database of SWCC parameters and relevant soil index properties with the M-EPDG software. Achieving this objective required, in turn, the pursuit of two complementary goals: Provide direct access to the maps and soil properties during the operation of the MEPDG software through an interactive use of coordinate points, defined by latitude and longitude, that which are input by the user of the M-EPDG. Inputting the coordinate points should then access a Google-based map that displays the soil units encountered in the area along
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with highway or route mileposts. A complete tabular summary of soil property data for the chosen location can also be obtained. Provide direct access to the maps and soil properties by using the official state milepost system. The user should be able to (a) identify a road segment through the official state milepost, (b) link the milepost to its respective latitude and longitude, and (c) access the Googlebased map that displays the soil units and highway system and a tabular summary of all relevant soil property data. Additionally, the present paper is intended to share with the pavement engineering community the key features and use of the search tool developed under NCHRP Project 9-23B.
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BACKGROUND
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Enhanced Integrated Climatic Model The EICM requires different input parameters to accurately adjust the stiffness of unbound and subgrade materials due to seasonal environmental changes. Although the EICM layout does not specifically define the input parameters by hierarchical level of analysis, the selection of such parameters can be achieved by following a general hierarchical approach as outlined in the final report for the NCHRP 1-40 D project (1). In that report, the following parameters are suggested for each level of analysis: Level 3: AASHTO soil classification, grain-size distribution, and Atterberg limits of the unbound/subgrade materials. These properties are expected to be measured by the user. Default values, based on AASHTO soil classification, are available within the EICM. Level 2: Specific gravity of solids, maximum dry density and optimum moisture content are required, in addition to the parameters required for Level 3. Default values for specific gravity of solids are available within the EICM. These values were gathered from textbooks and published literature. As for the compaction data (optimum moisture content and maximum dry density), default values based on AASHTO classification are also available. These values were derived from correlations with grain size distribution and consistency limits. Level 1: SWCC parameters from measured suction data are required, in addition to the parameters required for Level 2. Default values based on soil classification are available. Of all the soil properties needed to be input in the M-EPDG; the SWCC parameters are the least standardized and the most complicated set of inputs to be selected for the EICM analysis. The groundwater table depth is required as environmental parameter for all levels of analysis. This input is intended to be either the best estimate of the annual average depth or the seasonal average depth. For input Level 1, the groundwater table depth can be determined from profile characterization borings prior to design. Conversely, an estimate of the annual average value or the seasonal averages based on hydrologic regional maps should be sufficient as Level 3 input values.
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NCHRP Project 9-23A NCHRP Project 9-23A assembled an extensive database of unbound material property input data required for the M-EPDG (2). A full set of Level 3 data and most Level 1 and 2 information, including SWCC parameters and saturated hydraulic conductivity, was obtained. In addition, predicted typical resilient modulus and CBR values based on soil index properties were obtained and included as part of the database. This information was provided in the form of a national database and implemented via GIS soil unit maps for the entire United States and the
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Commonwealth of Puerto Rico. These data comprise 31,100 soil units mapped by the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS). The catalog of subgrade material properties provides regional and state transportation agencies with a tool to design better performing and more cost effective pavements through the use of a database established on measured materials properties rather than empirical relationships. The SWCC parameters contained in this database represent one of the largest collection of unsaturated soil material properties available in the world. Further analysis of parameters such as Group Index, grain-size distribution and Atterberg limits can better refine soil classification sub-divisions and yield better default parameters for use with the M-EPDG.
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Need for an Enhanced Searching Tool The development of the M-EPDG has been a great step towards a more reliable pavement design analysis. It is expected that the availability of the NCHRP 9-23A database to the M-EPDG user will greatly simplify the design and analysis processes, and will encourage the use of the guide. However, the new methodology needs a substantial amount of soil input parameters. Therefore, it became necessary the creation of a tool that simplifies the selection and extraction of soil properties data required to run the M-EPDG. This new searching tool will allow for the interactive use of GIS-based soil maps that can be easily accessed during the operation of the M-EPDG software system by adding a link to an Internet server. It also upgrades the capability of the M-EPDG to a new generation of operational simplicity and user friendliness.
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DEVELOPMENT OF THE SEARCH TOOL The development of the search tool was the result of completing a series of tasks grouped under five general activities. Such activities are conveniently synthesized in the following sections.
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Collection of Geographical Coordinates for the U.S. Road Network The national database developed in NCHRP Project 9-23A allowed retrieval of subgrade soil properties through a graphical search of state maps with a user interface running in Microsoft Excel®. First, the user selects a state map and then a geographic region within the state. Each regional map shows the soil units and their approximate locations within the region. Selecting a specific soil unit yields a tabular report of the soil property data for that unit. This project expanded the functionality of the national database to allow search and retrieval of soil property data at specific mileposts. To do this, a database was developed in which the U.S. road network is geographically referenced by coordinate points of latitude and longitude. The goal was to assign such a coordinate point to every milepost on the U.S. road network. The completed database includes such coordinate points in 46 states, the District of Columbia, and Puerto Rico. During the development of the database, it was found that several departments of transportation—Delaware, Florida, Louisiana, North Carolina, Pennsylvania, Puerto Rico, and West Virginia—no longer use the milepost reference system. These states and Puerto Rico provided data in the form of road segments rather than mileposts. The road-segment data were transformed to mileposts wherever possible. For those states that have never used milepost data, the collected information was left intact and a unique reference system was created, which allows the user to locate the point of interest by using the road segments historically used by the state, instead of mileposts.
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In some instances, not all road segments or mileposts were available, and the database is limited to the information collected during the duration of the NCHRP 9-23B project. However, despite the lack of milepost or route data for the aforementioned states, soil unit overlays were developed for all 50 states, the District of Columbia, and Puerto Rico, and these data can be retrieved for any location by inputting coordinates of longitude and latitude when milepost or road segment information are not available.
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Treatment and Organization of U.S. Road Network Data The U.S. road network data described above was checked for quality and then organized to make it compatible with the soil properties database developed in NCHRP Project 9-23A. In addition, improvements were made to the collected shapefiles (GIS format) to facilitate their use in developing the overarching computer code. The following activities were conducted: Data cleaning: The collected data were organized in tables and subsequently formatted to create the shapefiles. Data that were not relevant to the purposes of this research were deleted to simplify the process. Homogenization of data files: A standard formatting style was adopted and implemented for each state's data set. Each data table contains separate columns for latitude, longitude, state, road type (interstate, US highway, and state route), road number, and milepost number. For states that do not use a milepost system, an alternate format was adopted in which a road ID column containing the identification numbers for the road segments provided by the state agencies replaced the milepost number column. Generation of identifiers for road segments corresponding to the existing soil units: A unique identifier was created for each milepost, consisting of state abbreviation, road type, road number, and milepost number. For those states which provided road segments instead of milepost data, a similar unique identifier was also created, which consisted of the road segment ID assigned by the corresponding state DOT. Improvement and conditioning of collected shapefiles: Milepost data were geocoded and transformed into shapefiles in order to join the map feature to its corresponding soil unit data. Conversion of shapefiles into KML files: KML files are Google-compatible files used to overlay data in Google Earth and Google Maps. The creation of the KML files required an additional step in the project, involving the further conversion of the soil unit shapefiles collected in NCHRP Project 9-23A. All shapefiles were sorted by state and run through a web-based conversion software. Size and data limitations set by Google created an additional, unforeseen hurdle due to the large size of the files. The KML files for many states were too large by Google standards, so they had to be split into as many as 15 files per state. Of the 48 route data sets collected, the data from Texas and Puerto Rico were found to be unusable for the purposes of this project. Therefore, a total of 46 data tables were generated and converted into KML files. These tables can be found in the NCHRP 9-23B project final report (3).
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Development of a Code to Retrieve Data based on Geographical Coordinates Input A computer code was developed capable of performing a query in the database to retrieve relevant information corresponding to the soil unit map underlying the specific geographical location defined by the geographical coordinates input.
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A preliminary evaluation of the methodology needed to implement the code determined that the best option was to create a user interface capable of operating interactively. The code developed under this activity requires the user to perform the following steps: Input geographical location defined by the Geographical Coordinates (latitude and longitude). The interactive mechanism should command the mapping tool to zoom into the location of interest and insert a marker indicating the point under evaluation. The mapping tool loads an overlay of the soil units encountered in the geographic region. The user should be easily able to identify the underlying soil units located across the road segment under evaluation. Identify the soil unit of interest by clicking on the map. A unique identification code should be displayed for the chosen unit. Key and enter the identification code in order to retrieve all relevant data corresponding to the soil units of interest. The display of the data is possible through the use of a code described in following sections. Google Maps web service is the mapping tool used to display the soil unit maps. The interaction between the M-EPDG and Google Maps is expected to be relatively easy by means of a link within the M-EPDG software that opens the Soil Unit map webpage.
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Development of a Code to Retrieve Data based on Milepost Input A software routine was coded that is capable of performing a query in the database to extract relevant information corresponding to the soil units encountered in the road section of interest by using milepost input. This code requires the user to perform the following steps: Input the location defined by the milepost corresponding to the point of interest within the road segment under evaluation. The code performs a query to find the geographical coordinates corresponding to the milepost of interest. These geographical coordinates are then used in the mapping tool to display the region of interest. The interactive mechanism commands the mapping tool to zoom into the location of interest and to insert a marker indicating the milepost under evaluation. The mapping tool will load an overlay of the soil units encountered in the geographic region. The user identifies the underlying soil units located across the road segment under evaluation. Identify the soil unit of interest by clicking on the map. A unique identification code should be displayed for the chosen unit. Type the required ID code into the MapChar box and submit it in order to retrieve all the relevant data corresponding to the soil units of interest. The display of the data is possible through the use of a code described in following sections. The code development process concentrated on making the milepost query as userfriendly as possible, by reducing the number of steps the user must take to find the coordinates of interest. Thus, the milepost query page guides the user through the query process, all while reloading automatically. For example, to query a specific milepost, the user needs to select parameters from four different dropdown boxes. These parameters are State, Route Type, Route
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Number, and Milepost. Once the user selects the relevant state from the first dropdown box on the query page, the page automatically reloads and limits the choices in the next dropdown box (Route Type) to those available for the selected state. Once the Route Type is selected, the page again reloads and limits the choices in the milepost dropdown box. Once the user selects the milepost, the latitude and longitude for that milepost will display automatically. Although more labor and time intensive, the dynamic dropdown boxes allow ease of use, prevent errors, and reduce mouse-clicks.
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Development of a Code to Display Soil Unit Data A software routine was coded to display the results of the query performed by running the code described in the previous section. The database from NCHRP Project 9-23A was converted to SQL format files. The SQL format is supported by web servers and is searchable. The database was then uploaded to the server, and a connection between the webpage and database was coded. As a result, a summary of the soil properties available in the database for the soil unit of interest can be displayed in the screen. This summary may then be printed as an aid to inputting the data in the M-EPDG or DARWin-ME.
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A flowchart summarizing the work performed to develop the search tool is presented in Figure 1. As previously explained, for some states it was not possible to either obtain Milepost data or utilize the Milepost data available for the purpose of this research. However, the soil unit overlays were developed for every single state and therefore, the data can be retrieved by inputting the coordinates or by specifying the state needed.
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IMPLEMENTATION OF THE SEARCH TOOL INTO THE M-EPDG VIA MILEPOST, ROAD SEGMENT, OR GEOGRAPHICAL COORDINATES Ideally, the computer code described in the previous sections could be implemented to work interactively with the M-EPDG. This implementation would involve changing the M-EPDG interface to allow inputting the milepost, road segment, or geographical coordinates of the project and retrieving the relevant soil unit data summary for direct use by the M-EPDG. However, given the 2011 release of the M-EPDG as the commercial DARWin-ME software, this implementation was not possible under NCHRP 9-23B project. Instead, a web-based interface was developed from which all the data created in this project can be easily retrieved and inputted to the DARWin-ME software. This permits the use of the database not only by the DARWin-ME user but also by anyone interested or in need of a preliminary assessment of the soil conditions when designing a new pavement or performing rehabilitation activities. For review, the following link to the web-based interface is temporarily operational and available: http://nchrp923b.lab.asu.edu/index.html.
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USE OF THE SEARCH AND RETRIEVAL TOOL This section presents detailed instructions on how to operate the interactive tool to search for and retrieve in-situ soil properties required by the M-EPDG and DARWin-ME. The tool can be independently accessed through any Web browser available to the user. The following steps are required to search and retrieve the soil input parameters for the pavement design and analysis process: 1. Access the interactive searching tool by visiting the following link: http://nchrp923b.lab.asu.edu/index.html. The web portal will load, as shown in Figure 2.
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2. The data query can be performed either by inputting Geographical Coordinates or by using Milepost markers from the US Road Network. When using Geographical Coordinates, the user selects the desired state from a dropdown box menu, as shown in Figure 3(a). 3. Enter the latitude and longitude corresponding to the point of interest. The coordinates must be entered using decimal degrees, as shown in Figure 3(b). 4. Once the desired state has been selected and the geographical coordinates inputted, click the Get Map button and the interactive mechanism will command the mapping tool to zoom into the location of interest. A marker indicating the location will be displayed. The mapping tool will load an overlay of the soil units encountered in the area, as shown in Figure 3(c). The soil unit overlay may take several seconds to a minute to load. If the geographical coordinates are unknown to the user, the U.S. road network implemented in the search tool can be used to perform the data query by clicking on the Search for Milepost Coordinates button, as shown in Figure 4(a). 5. The Search for Milepost Coordinates link will automatically open a new window, as shown in Figure 4(b). 6. Select the state, route type, route number, and the milepost marker from the data available for each state, as shown in Figure 5(a). 7. As soon as the required information is entered, the geographical coordinates corresponding to that particular milepost will be provided by the search tool, as shown Figure 5(b). 8. Detailed information about each state’s data is available to the user by clicking on the link here located above the Close button, as indicated in Figure 5(b). The link will automatically open a new window that presents nomenclature information for Route Type, Route Number and Milepost/Road segment data. 9. Copy and paste the coordinates provided by the milepost search tool into the corresponding Latitude/Longitude boxes on the search tool's main page as shown in Figure 2. The user can then click the Get Map button. The tool will load an overlay of the soil units encountered in the geographic location, as shown in Figure 6(a). 10. Once the soil units map is loaded, the user can use the slide bar to zoom in and out, or grab the map to pan. The user should be able to identify the underlying soil units located across the road segment under evaluation. By clicking on the soil unit of interest, its unique identification code (MapChar code) will be displayed, as shown in Figure 6(a). 11. Input the identification code into the MapChar box, as shown in Figure 6(b). 12. Click the Get Report button to generate the Soil Unit report in a separate window, as shown in Figure 7(a). 13. The user has two options: print out the report (Print Report) or close the window (Close). These buttons are found at the bottom of the Soil Unit report window as shown in Figure 7(b). If the window is closed, the user will be re-directed to the main page. The data generated in the report include the AASHTO classification and Group Index; the thickness of each sub-layer in the profile; groundwater table depth; grain-size distribution parameters such as percent passing #4, #10, #40, #200 and clay content; Atterberg limits; saturated hydraulic conductivity; volumetric water content or porosity; and the SWCC parameters af, bf, cf and hr. Also, CBR and resilient modulus values are estimated from index properties. A thorough explanation of the data obtained can be found in the original report (3).
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CONCLUSIONS The results of this study provide state engineers, industry and researchers with an interactive search tool to extract unbound material property input data required for the M-EPDG. The database integrated in the search tool is the final product of the NCHRP 9-23A project and contains a full set of Level 3 data and most Level 1 and 2 information, including SWCC parameters and saturated hydraulic conductivity. This information was initially provided in the form of a national database implemented via GIS Soil Unit Maps for the entire United States and Puerto Rico. The data comprises 31,100 soil units extracted from The U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS). As part of NCHRP Project 9-23B, an interactive search tool was developed to integrate the GIS-enabled national database of Soil Water Characteristic Curves and relevant soil index properties with the M-EPDG software. Google Maps web service is the mapping tool used in this project to display the soil unit maps. The interaction between the M-EPDG and Google Maps is expected to be easily implementable and a great enhancement for the design tool program. Excellent and innovative implementation efforts have already started at the state level (4) with data provided by the authors. The search tool provides direct access to the maps and soil properties during operation of the M-EPDG software through interactive use of the M-EPDG user-input coordinate points (defined by latitude and longitude). It makes use of the input coordinates of latitude and longitude to access both the appropriate soil unit map and a complete tabular summary of soil property data at that particular location. The tool is also capable of identifying each road segment by its official state mileposts and link the mileposts to their respective latitude and longitude and soil unit areas, making it possible for the user to input a specific highway or route milepost and immediately access the major soil unit map located at that route milepost and a tabular summary of all relevant soil property data. It should be mentioned that since the milepost marker data available was limited, the milepost search feature does not work for the entire U.S. road network. However, the milepost marker database can be continuously updated as more data becomes available.
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RECOMMENDATIONS FOR FUTURE ENHANCEMENTS The product of this research project is the first version of an interactive soil searching tool that can be further enhanced not only by periodically updating the database but also by implementing new features to simplify its operation. Some recommendations are given in this section.
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Upgrading the Soil Property Database The soil property database used to develop the search tool was entirely based on the database collected, stored, maintained, and distributed by the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS). The NRCS database is an excellent source for determining the regional distribution and general characteristics of soils for urban and rural engineering projects. The NRCS information is divided into three soil geographic databases that primarily differ in the scale used for mapping the different soil units. The three soil geographic databases are: The Soil Survey Geographic (SSURGO) database, The State Soil Geographic (STATSGO) database, and The National Soil Geographic (NATSGO) database.
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The components of map units in each database are different and correspond to a differing level of detail. The SSURGO database, for example, provides the most detailed level of information while NATSGO has a somewhat lower level of detail and is primarily used for national and regional resource appraisal, planning, and monitoring. The information used in this project is based on the National Soil Geographic (NATSGO) database. Therefore, there is opportunity for upgrading the database to STATSGO or even the SSURGO level in the future.
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Updating the U.S. Road Network Milepost Marker Database As previously mentioned, the milepost marker information used for this project is limited by the fact that some state DOTs make use of a different referencing system. It is expected that DOTs will continuously improve their databases, which will allow updates to the road network database in the future.
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Implementing a Direct Input Feature from the M-EPDG Interface to the Search Tool The search tool developed in this study was intended to be linked to the M-EPDG software originally issued for public evaluation in 2004. This software is no longer available, having been superseded by DARWin-ME in September 2011. Even though the search tool developed here functions independently of either the M-EPDG or DARWin-ME, adding a link from either program to the web-server where the tool is available should not be difficult and will greatly improve the input process.
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Enhancement of Data Retrieving Methodology and Visual Display Currently, the interactive tool is capable of performing the data search for a single location at a time. Ideally, the tool should be able to search for multiple locations at the same time. This enhancement would save time and resources when the project being designed is of considerable size.
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ACKNOWLEDGEMENT This study was supported by the National Cooperative Highway Research program under the NCHRP 9-23B project. The authors would like to acknowledge and thank the support, guidance and edits of our NCHRP Program Manager, Dr. Ed Harrigan. Also, the authors express their gratitude to Natalie Lopez and Gustavo Torres, student workers at ASU, who went far and beyond in helping to generate and develop both the soil property searching tool and the database.
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REFERENCES 1. Witczak, M.W., C.E. Zapata, and W.N. Houston. Models Incorporated into the Current Enhanced Integrated Climatic Model: NCHRP 9-23 Project Findings and Additional Changes after Version 0.7, NCHRP Project 1-40D(01), Final Report. Transportation Research Board, National Research Council, Washington, D.C., 2006.
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2. Zapata, C.E. A National Catalog of Subgrade Soil-Water Characteristic Curve (SWCC) Default Inputs and Selected Soil Properties for Use with the M-EPDG, NCHRP Project 923A, Final Report. Transportation Research Board, National Research Council, Washington, D.C., 2010.
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3. Zapata, C.E., and C.E. Cary. Integrating the National Database of Subgrade Soil-Water Characteristic Curves and Soil Index Properties with the M-EPDG, NCHRP Project 9-23B, Final Report. Transportation Research Board, National Research Council, Washington, D.C., 2012.
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4. Jadoun, F.M. and Kim, Y.R. GIS-Based Implementation Methodology for the NCHRP 923A Recommended Soil Parameters for Use as Input to the MEPDG in North Carolina. Transportation Research Board annual meeting, Annual Meeting DVD, Washington D.C., January 2011.
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LIST OF TABLES AND FIGURES FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7
Flowchart of the work performed to develop the search tool. Search tool main web portal. Data search by using geographical coordinates. Use of milepost search option. Retrieval of geographical coordinates using milepost data. Soil unit selection and data retrieval. Display of soil unit data summary and print option.
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Collect milepost data from DOTs
Collect soil unit shapefiles from NCHRP 9-23A
Collect database from NCHRP 9-23A
Clean data
Convert shapefiles to KMLs and format
Convert to SQL format
Standardize format Create a code to display the soil properties summary
Create milepost and segment identifiers
Geo-code milepost and segment data
Format milepost data and convert to SQL
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Create webpage and add SQL tables and KML files Allow user to generate map and report
FIGURE 1 Flowchart of the work performed to develop the search tool.
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FIGURE 2 Search tool main web portal.
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(c) FIGURE 3 Data search by using geographical coordinates.
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FIGURE 4 Use of milepost search option.
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FIGURE 5 Retrieval of geographical coordinates using milepost data.
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FIGURE 6 Soil unit selection and data retrieval.
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FIGURE 7 Display of soil unit data summary and print option.
