Johnson, David M.

The Minnesota Department of Transportation (Mn/DOT) began construction on the Minnesota Road Research Project (MnROAD) in 1991 and opened the full-scale pavement research facility to live traffic in 1994. Since the time of its construction, MnROAD, the first major test track since the AASHO Road Test of the 1950s and 1960s, has learned many lessons in pavement testing and pavement engineering on behalf of the greater pavement community. Researchers at the University of Minnesota reviewed these lessons from the first phase of MnROAD (the facility's first ten years of operation) for a project titled MnROAD Lessons Learned. The Lessons Learned project involved over fifty interviews, three hundred published and unpublished reports, papers, and briefs, and an online survey of pavement professionals. This paper, based on the Lessons Learned project, presents a sample of the lasting benefits of MnROAD at the local, state, and national levels. Furthermore, the paper provides extensive references for these benefits in hopes of increasing awareness of this pavement test facility's under-publicized contributions to pavement engineering. This paper was submitted for the Transportation Research Board 2008 Annual Meeting.

Falling Weight Deflectometer (FWD) data and the corresponding pavement stiffness moduli and deflection basin areas vary as functions of both time and space. This paper focuses primarily on extracting information from the spatial variability of FWD deflection data. Spatial variability occurs both horizontally and vertically within a pavement system; it is inherent in the system due to the heterogeneity of the material composing the subgrade. and is further influenced by the construction process and the resulting variations in density, moisture content, and thickness of the subbase, base, and surface layers. To assess spatial variability of just the subgrade and then the overall pavement structure, FWD tests were conducted on 71 test points on top of each of the layers composing a pavement system. and a statistical analysis was conducted on the data. Test pavements included two mainline (five-year design) and two low-volume test cells at the Minnesota Road Research Project (MN/ROAD). By comparing differences between pairs of measured deflections at increasing test point separation distances. one can incorporate distance weighting techniques into a statistical form frequently used in the fields of geology and mining. The geostatistical semi-variogram can be applied to pavements and used to model the degree of correlation between data at any two test points. As the distance between test points increases, corresponding data become decreasingly dependent upon each other until, at some appreciable distance. they are independent of each other. From the semi-variogram. one can readily determine the separation distance at which values are independent of each other. Conventional statistical analyses are also used to supplement geostatistical techniques. Valuable and cost-saving information can be acquired by analyzing baseline FWD data with this technique. The efficiency of future FWD testing can be maximized, and optimum FWD test point spacing can be determined for pavement evaluation and overlay design. Furthermore, the geostatistical techniques discussed are applicable to any problem involving the distribution of a variable in one. two, or three dimensions.

The Dynamic Cone Penetrometer (DCP) is a test device used for measuring the strength and variability oh unbound layers of soil and granular material. The DCP is not a new test device, but transportation organizations in Canada and the United Stales, including the Strategic Highway Research Program (SHRP), have shown a renewed interest in its unique capability of measuring a profile of in situ foundation characteristics. A desire to more fully characterize subsurface conditions on the Minnesota Road Research Project (Mn/ROAD) led to the initial use of DCP by Mn/DOT. From an operational perspective it is very attractive because the DCP is both portable and simple to use. The objective of this research was to explore ways that IXP's could effectively be used by Minnesota pavement and materials engineers and to perform the testing, analysis, and learning necessary for establishing relationships between DCF' test results and other commonly used foundation parameters. This paper describes the design and operation of the DCP as well as an overview of the theoretical basis for use of the device. In addition, correlation results, data profiles, case histories and related information are presented.

The Minnesota Department of Transportation is investigating alternative means of culvert renewal in lieu of removal and replacement. Several state of the art renewal techniques were selected for trial on 1-35 near Hinckley, Minnesota in an effort to find an inexpensive and less disruptive alternative to removal and replacement of deteriorated culverts. Seven different reliners were placed in concrete and metal pipe, and five joint repair options were placed in concrete pipe. These reliners and repairs were compared using costs, skills and resources required, time, culvert preparation, traffic disruption, work area requirements, placement problems, and grouting procedures. Field performance of the reliners and joint repairs was checked visually after one year to evaluate the short term effects of climate. At this point in time all reliners appeared to be performing adequately. Relining and joint repair should be considered as an inexpensive, time saving, and minimally disruptive alternative to removal and replacement of deteriorated culverts. Smooth reliners are inexpensive, flexible, easy to install and perform better hydraulically than corrugated or ribbed reliners. Savings can be significant in both money and time with very little disruption to the driving public.

In December 2003 the LRBB and Mn/DOT's Office of Materials allocated resources for a five-year project to identify, locate, describe, and track research test sections and other unique sites of interest on Minnesota (state and local) roadways. This became Investigation 809, Research Tracking for Local Roads. As the first step, Mn/DOT staff developed a database with a Web based user interface for entering and retrieving site data. The database was completed in 2004 and some individuals began to enter data into the database. With LRRB funds, a consultant was hired in November 2006 to facilitate and accelerate the collection, validation, and entry of data and also to make recommendations for database improvements. This report summarizes the efforts of that consultant. A number of recommendations are made in this report for improving the database and its user interface and for insuring that the database is robust. Each test section (site) in the database represents a significant investment of resources to design and construct something unique. Each site in the database may be of interest to other jurisdictions. Once constructed it could take years before the ultimate performance of a site can be determined. Meanwhile, champions change jobs and priorities change. This report raises a key question: How can we ensure a return on the investments made in site design and construction?