Browsing by Subject "Shear strength"

Now showing 1 - 4 of 4
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    BR27568 – Experimental Shear Capacity Comparison Between Repaired and Unrepaired Girder Ends
    (Minnesota Department of Transportation, 2018-02) Shield, Carol; Bergson, Paul
    Over time, the southbound exterior girder ends on each side of Pier 4 and Pier 26 of Bridge 27568 suffered significant corrosion damage that exposed transverse reinforcement, prestressing strands in the exterior side of the bottom flange and the sole plate anchorages. The girder ends were repaired in 2013 by encasing supplementary steel reinforcement in shotcrete over a 4 ft. length of the girder. The two repaired girders and two companion girders, removed when the bridge was replaced in 2017, were brought to the University of Minnesota and tested to failure in shear to determine the effectiveness of the repair. The laboratory testing showed that the repair was able to return the girders with significant corrosion damage to the strength of the companion girders, indicating that the repair was effective.
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    Hydraulic and Mechanical Properties of Recycled Materials
    (Minnesota Department of Transportation, 2009-10) Gupta, Satish; Kang, Dong Hee; Ranaivoson, Andry
    Construction and maintenance of roads requires large volume of aggregates for use as base and subbase materials. Because of the cost of virgin aggregates, federal and state agencies are encouraging the recycling of waste materials including materials in old pavements. This study assessed the suitability of four recycled materials relative to virgin aggregates for use as base and subbase materials. The four recycled materials were the reclaimed asphalt pavement (RAP), fly ash (FA), reclaimed concrete material (RCM), and foundry sand (FS). Assessment of these materials was done in terms of their hydraulic, mechanical, and leaching properties when mixed in with various proportions of virgin aggregates. Except for slightly higher fine content in some RAP-aggregate mixtures, particle size distribution of all mixtures was within the Mn/DOT specification band for Class 5 materials. Water retention (pore size distribution), hydraulic conductivity, resilient modulus, and shear strength measurements were generally similar to that of 100% aggregates. Exception was the mixtures of FS. Heavy metal concentrations in the leachate were also generally less than the EPA drinking water standards. We concluded that FA, RAP, and RCM mixtures will be good substitutes of virgin aggregates as base and subbase materials.
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    Pavement Design Using Unsaturated Soil Technology
    (Minnesota Department of Transportation, Research Services Section, 2007-05) Gupta, Satish; Ranaivoson, Andry; Edil, Tuncer; Benson, Craig; Sawangsuriya, Auckpath
    Pavements are constructed on compacted soils that are typically unsaturated. The negative pore-water pressure (soil suction) due to the ingress of water in between soil particles has a significant effect on pavement foundation stiffness and strength. The study characterized the effects of soil suction on shear strength and resilient modulus of four soils representing different regions of Minnesota. The deviator stress in shear strength measurements followed a power function relationship with soil suction. Resilient modulus also followed the power function relationship with suction but these relationships fell within a narrow range. We present models for incorporating suction effects in shear strength and resilient modulus measurements of highly compacted subgrade soils. We also briefly outline a framework for incorporating these models in the resistance factors of MnPAVE. Since soil water content and the resulting soil suction under the pavement varies with season, adjustments are needed to account for increased strength and stiffness of the material as a result of unsaturated soil conditions. These adjustments will not only reflect the more realistic field conditions but will result in more reliable performance predictions than the current pavement design method.
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    Slope Stabilization for Local Government Engineers in Minnesota
    (2017-05) Nelson, Mitchell
    Slope failures cause infrastructure damage, pose safety risks, and produce preventable maintenance costs. The purpose of this research was to recommend methods for stabilizing locally-maintained slopes requiring recurring maintenance in Minnesota. The author used input from county and municipal engineers to determine common techniques and identify slope failure examples. Site investigations helped develop case studies to analyze slope stabilization methods. Laboratory testing characterized representative soil strength properties. Additionally, the author developed Limit Equilibrium Method models for each slope to investigate different stabilization methods in a parametric study. Finally, modeling and analysis results were summarized in a guide for local government engineers. The target audience of the guide is county or local municipal engineers that do not have specialized geotechnical engineering experience. Additionally, modeling software enabled the development of slope stability charts specific to roadway embankments. The stability charts and guide will assist engineers in improving slope stability for roadway embankments.