Numerical modelling of the nonlinear mechanical behavior of multilayer geosynthetic system for piggyback landfill expansions

Numerical modelling techniques have been increasingly used to assess the integrity of engineering works, such as landfills, that involve interactions between multiple geosynthetics GSYs). In piggyback landfill expansions (PBLEs), where a new landfill is built over an older one, such interactions are particularly important because multiple GSYs, natural materials, and waste interact with each over. To obtain reliable numerical results, the real mechanical behavior of the GSYs and of the interfaces between GSYs must be considered. Designers, however, often use simplistic assumptions without further analyzing the implications of these assumptions on the results. Such simplifications mainly concern the nonlinear axial stiffness of GSYs, the strain softening at interfaces between GSYs, and the difference between the compressive and tensile behavior of GSYs. By, considering these key aspects, the present study aims to understand the extent to which the results of numerical calculations can be influenced both by the differing compressive and tensile behavior of GSYs and by the assumption of strain softening at interfaces between GSYs. For this purpose, several numerical models are implemented by using the finite-difference code FLAC 2D on a typical PBLE that involves four GSYs and six interfaces. The present work also applies comprehensive, state-of-the-art numerical modelling to study the interactions between multiple layers of GSYs. This study also investigates the nonlinear axial stiffness of GSYs through a series of uniaxial tensile tests. The numerical results show that, if the GSY axial compressive and tensile characteristics are the same, then tensile force is minimized, which induces significant compressive force in the GSYs. The results also indicate that neglecting strain softening at the interface between GSYs affects interface shear stresses, displacements of GSYs at the interface, and the GSY force distribution, potentially rendering the model unrealistic. Including strain softening, however, allows the assessment (location) of unstable areas along the interface where large displacements occur

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Book reviews of: William F. Winter and the New Mississippi: A Biography. By Charles C. Bolton Jackson: University Press of Mississippi, 2013. Pp. vii, 368. Illustrations, map, acknowledgements, notes, index. $35.00 cloth. ISBN: 9781617037870. Born of Conviction: White Methodists and Mississippi’s Closed Society. By Joseph T. Reiff. (New York: Oxford University Press, 2016. Acknowledgements, illustrations, map, notes, index. Pp. xxi, 384.$35 Hardcover. ISBN: 9780190246815). In Katrina’s Wake: The U.S. Coast Guard and the Gulf Coast Hurricanes of 2005. By Donald L. Canney. (Gainesville: University Press of Florida, 2010. Foreword, notes, index. Pp. xv, 228. $27.50 cloth.) Slavery, Race and Conquest in the Tropic: Lincoln, Douglas and the Future of America. By Robert E. May. (New York: Cambridge University Press, 2013. Acknowledgements, illustrations, maps, notes, index. Pp. xi, 296.$80 cloth, $26.99 paper,$22 e-book. ISBN: 9780521132527.) Rivers of Sand: Creek Indian Emigration, Relocation, and Ethnic Cleansing in the American South. By Christopher D. Haveman. (Nebraska: University of Nebraska Press, 2016. Illustrations, preface, acknowledgments, notes on terminology, index. Pp. ix, 414. Trouble in Goshen: Plain Folk, Roosevelt, Jesus, and Marx in the Great Depression. By Fred C. Smith (Jackson: University Press of Mississippi, 2014. Acknowledgements, illustrations, map notes, index. Pp. xi, 214. $60.00 cloth. ISBN: 9781617039560.) Builders of a New South: Merchants, Capital, and the Remaking of Natchez, 1865-1914. By Aaron D. Anderson (Jackson: University Press of Mississippi, 2013. Acknowledgments, illustrations, photographs, notes, graphics, index. Pp. 279.$40 cloth. ISBN: 978-1- 61703-667-5.) Adventurism and Empire: The Struggle for Mastery in the Louisiana- Florida Borderlands 1762-1803. By David Narrett. (Chapel Hill: The University of North Carolina Press, 2015. Acknowledgements, illustrations, notes, index. Pp. xi, 365. $45 cloth,$44.99 e-book. ISBN: 978-1-4696-1833-3.) Empty Sleeves: Amputation in the Civil War South. By Brian Craig Miller. (Athens: University of Georgia Press, 2015. Illustrations, acknowledgments, appendix, notes, index. Pp. xvi, 257. $79.95 cloth,$29.95 paper. ISBN: 0820343327.) Signposts: New Directions in Southern Legal History. By Sally E. Hadden and Patricia Hagler Minter, eds. (Athens and London: The University of Georgia Press, 2013. Acknowledgements, illustrations, index. Pp. xi, 480. $69.95 cloth,$26.95 paper, $26.95 ebook. ISBN: 978-0-8203-4499-7.) The Color of Christ: The Son of God and the Saga of Race in America. By Edward J. Blum and Paul Harvey. (Chapel Hill: University of North Carolina Press, 2012. Pp. 325.$32.50 Cloth. ISBN: 9780807835722.

Numerical modeling of the nonlinear mechanical behavior of multilayer geosynthetic system for piggyback landfill expansions

This paper was accepted for publication in the journal Geotextiles and Geomembranes and the definitive published version is available at http://dx.doi.org/10.1016/j.geotexmem.2016.07.004.Numerical modelling techniques have been increasingly used to assess the integrity of engineering works, such as landfills, that involve interactions between multiple geosynthetics GSYs). In piggyback landfill expansions (PBLEs), where a new landfill is built over an older one, such interactions are particularly important because multiple GSYs, natural materials, and waste interact with each over. To obtain reliable numerical results, the real mechanical behavior of the GSYs and of the interfaces between GSYs must be considered. Designers, however, often use simplistic assumptions without further analyzing the implications of these assumptions on the results. Such simplifications mainly concern the nonlinear axial stiffness of GSYs, the strain softening at interfaces between GSYs, and the difference between the compressive and tensile behavior of GSYs. By, considering these key aspects, the present study aims to understand the extent to which the results of numerical calculations can be influenced both by the differing compressive and tensile behavior of GSYs and by the assumption of strain softening at interfaces between GSYs. For this purpose, several numerical models are implemented by using the finite-difference code FLAC 2D on a typical PBLE that involves four GSYs and six interfaces. The present work also applies comprehensive, state-of-the-art numerical modelling to study the interactions between multiple layers of GSYs. This study also investigates the nonlinear axial stiffness of GSYs through a series of uniaxial tensile tests. The numerical results show that, if the GSY axial compressive and tensile characteristics are the same, then tensile force is minimized, which induces significant compressive force in the GSYs. The results also indicate that neglecting strain softening at the interface between GSYs affects interface shear stresses, displacements of GSYs at the interface, and the GSY force distribution, potentially rendering the model unrealistic. Including strain softening, however, allows the assessment (location) of unstable areas along the interface where large displacements occur

Growing meadowfoam in the Willamette Valley

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