Browsing by Subject "Shear stress"

Now showing 1 - 2 of 2
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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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    Peak shear and peak flow mediated dilation: a time course relationship
    (2014-05) Evanoff, Nicholas George
    Flow-mediated dilation (FMD) is a measure of endothelial function. This study aimed to explore the temporal relationship of time to peak FMD (FMDTTP) as well as time to peak shear stress (ShearTTP) between children and adults. Shear stress and FMD was assessed in 122 children and 350 adults using ultrasound. A p-value of 0.05 denoted significance. Peak FMD (p=0.022) and Peak Shear rate (p=0.0002), and were significantly larger in children than adults. FMDTTP was significantly slower (p=0.027) in children vs. adults. ShearTTP was slower in children than in adults (p=0.004). There was no significant difference (p=0.27) in time from ShearTTP to FMDTTP between children and adults. In the present showed children not only displayed a larger peak FMD, but also the time it takes the shear stimulus to reach its peak is significantly slower in children than adults. However, the time from peak Shear to peak FMD was similar.