Quality Control/Assurance on Base Course and Embankment With the Dynamic Cone Penetrometer
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2021-11-01
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Edition:Final Report 09/2018 – 06/2021
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Abstract:Nuclear moisture-density gauges (NDG) operate with the use of radioactive materials that may be hazardous to the health of the operators under certain circumstances. There is a need for test procedures using devices that are accurate, easy-to-use, economically sound, and nonradioactive. This research investigated using the Dynamic Cone Penetrometer (DCP) as a possible alternative for current quality assurance (QA) processes in embankment and base course test procedures, which currently utilize radioactive devices. The DCP as a QA compaction tool has several advantages over a nuclear gauge. These advantages include reduced safety concerns, reduced training requirements, and no intense federal regulations or licensing. The Indiana and Minnesota Departments of Transportations both have established specifications utilizing the DCP as an acceptance tool for soil layers, which guided researchers toward establishing a procedure for Louisiana. Louisiana Transportation Research Center researchers determined a “Limiting DCP Index” (mm/blow) parameter for different types of soil layers. These limiting thresholds were developed based on field acceptance compaction test results from the NDG and comparisons/similarities. The project’s fieldwork correlated well with these existing specifications, and thus, DOTD TR 645, a test method for utilizing the DCP, was modified to include a method (Method B) for compaction acceptance. Costs and benefits were also evaluated in this research. The DCP’s cost was significantly less than that of the NDG. The NDG requires approximately $9,000 per year for thermoluminescent dosimeters and licensing certification and roughly $9,000 - $25,000 for safety training classes that run on a three-year training cycle. The DCP does not require these safety measures. Based on the results and conclusions, researchers recommend the DCP as an alternative tool for compaction acceptance to the current NDG acceptance testing process. The DCP acceptance procedure is outlined in the modified specification: TR-645 Method B. In following this recommendation, pilot projects should be selected to test and refine the draft specification and test method. In this case, the project could utilize the DCP for acceptance and pay, and have the NDG shadow the DCP for research purposes.
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