Browsing by Author "Labuz, Joseph F."
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Item Fabric for Reinforcement and Separation in Unpaved Roads(1998-12-01) Bearden, Julie; Labuz, Joseph F.Researchers performed laboratory experiments on soil-fabric-aggregate systems to evaluate the effect of a geotextile on unpaved road performance. Direct shear tests performed on gravel indicated a 42-degree friction angle. Similar tests performed on soil-fabric-aggregate systems resulted in an interface friction value for the nonwoven geotextile system similar to that of the gravel alone. The slit film and heavy weight woven systems generated friction angles about 20 percent lower. Observations of model tests showed that in terms of rut depths, the nonwoven performed better than the slit film woven geotextile for all gravel thickness', most likely because of the nonwoven's higher frictional characteristics. The rut diameters for the slit film and nonwoven reinforced systems tended to be larger than those observed for the unreinforced systems indicating an increased load-spread angle through the gravel. Based on rutting alone, the unreinforced model with 200 mm (8 in.) gravel was equivalent to that of the slit film in reinforced model with 150 mm (6 in.) gravel and the nonwoven model with 100 mm (4 in.) gravel. A so-called bearing capacity factor for the unreinforced models was approximately 50 percent less than the nonwoven reinforced models, in reasonable agreement with theory.Item Intelligent Compaction Implementation: Research Assessment(Minnesota Department of Transportation, 2008-07) Labuz, Joseph F.; Guzina, Bojan; Khazanovich, LevThe objective of this project was to provide a qualitative assessment of the Minnesota Department of Transportation’s Intelligent Compaction (IC) Specifications. IC is an attractive approach to evaluate the compaction quality because it involves continuous and instantaneous evaluation of the soil through machine-drive power or drum vibration monitoring. Four construction sites utilizing IC were visited: (1) TH 36 in North St. Paul, involving both granular and nongranular soils; (2) US 10 in Staples, with granular soil; (3) TH 60 in Bigelow, with nongranular soil; (4) US 10 in Detroit Lakes, involving both granular and nongranular soils. The report integrates comments from the four site visits and provides an interpretation on the use of IC at each site. As the technology now exists on the equipment used at these locations, IC provides only an index, which is specific to the conditions associated with a particular site. An interpretation of comments provided the basis for the following recommendations: • Use light weight deflectometers (LWD) for quality assurance of stiffness • Establish a procedure to determine the target LWD value • Eliminate calibration areas (control strips) • Simplify IC data evaluation and presentation • Calibrate the IC roller and related transducers • Support development of alternative IC methodologies • Simplify or eliminate moisture correctionsItem A Review of Instrumentation Technology for the Minnesota Road Research Project(1992-04) Van Deusen, David A.; Newcomb, David E.; Labuz, Joseph F.This report presents a literature review of instrumentation practices for the measurement of stresses, strains, and deflections in pavement structures. Various types of instruments that are commonly employed in pavement instrumentation projects are discussed, as well as the factors that influence their performance. In a series of laboratory experiments, the performance of three different types of embedment strain gages, two LVDTs, and one soil stress cell are investigated. These experiments are designed to evaluate the accuracy and durability of commercially available transducers. For strain gages, the selection of an appropriate transducer must balance compliance and measurement sensitivity. All of the strain gages tested in concrete gave reasonable results. It was found that hermetically sealed LVDTs should be sufficient enough for robust installations. Experiments with soil stress cells embedded in sand indicate the variability that may be expected in the field due to installation procedures, and emphasize the need for in-soil calibrations. A set of recommendations are provided with respect tot the sensor procurement and installation specifications for Mn/ROAD.Item Structural Evaluation of Asphalt Pavements with Full-Depth Reclaimed Base(Minnesota Department of Transportation, 2012-12) Tang, Shuling; Cao, Yuejian; Labuz, Joseph F.Currently, MnDOT pavement design recommends granular equivalency, GE = 1.0 for non-stabilized full-depth reclamation (FDR) material, which is equivalent to class 5 material. For stabilized full-depth reclamation (SFDR), there was no guideline for GE at the time this project was initiated (2009). Some local engineers believe that GE of FDR material should be greater than 1.0 (Class 5), especially for SFDR. In addition, very little information is available on seasonal effects on FDR base, especially on SFDR base. Because it is known from laboratory studies that SFDR contains less moisture and has higher stiffness (modulus) than aggregate base, it is assumed that SFDR should be less susceptible to springtime thawing. Falling Weight Deflectometer (FWD) tests were performed on seven selected test sections on county roads in Minnesota over a period of three years. During spring thaw of each year, FWD testing was conducted daily during the first week of thawing in an attempt to capture spring thaw weakening of the aggregate base. After the spring thaw period, FWD testing was conducted monthly to study base recovery and stiffness changes through the seasons. GE of SFDR was estimated using a method established by MnDOT using FWD deflections, and the GE of SFDR is about 1.5. The value varies from project to project as construction and material varies from project to project. All the materials tested showed seasonal effects on stiffness. In general, the stiffness is weaker in spring than that in summer and fall.