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Jialiang Shi - One of the best experts on this subject based on the ideXlab platform.

  • Shear strength and failure mechanism of needle punched geosynthetic clay liner
    Geotextiles and Geomembranes, 2020
    Co-Authors: Shijin Feng, Jiyun Chang, Yang Shen, Hongxin Chen, Jialiang Shi
    Abstract:

    Abstract The Internal Shear strength of a geosynthetic clay liner (GCL) within composite liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the Shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct Shear tests with five normal stress levels (250–1000 kPa) and eight displacement rates (1–200 mm/min) were conducted. The Shear stress to horizontal displacement relationships exhibit well-defined peak Shear strengths and significant post-peak strength reductions. The monitoring results of the thickness change indicate that the degree of volumetric contraction is related to the reorientation of fibers and dissipation of pore water pressure. Furthermore, the peak and residual Shear strengths both depend on the displacement rate because of the rate-dependent tensile stiffness of needle-punched fibers and Shear strength of the soil/geosynthetic interface. Through additional tests and lateral comparison, it was discovered that the Shear behavior of sodium bentonite, degree of hydration, and pore water pressures all affect the Shear mechanisms of the NP GCL. In particular, the failure mode transfers from fiber pullout to fiber rupture with the increase in water content as the hydrated bentonite particles facilitate the stretching of needle-punched fibers.

  • experimental study of Shear strength of geosynthetic clay liner for monotonic loading
    The International Congress on Environmental Geotechnics, 2018
    Co-Authors: Jiyun Chang, Shijin Feng, Yang Shen, Hao Shi, Jialiang Shi
    Abstract:

    Internal Shear strength of geosynthetic clay liner (GCL) is of vital importance for the stability of waste containment facilities where GCLs are widely used as hydraulic barriers. This paper presents an experimental investigation of the Internal Shear strength of hydrated needle-punched geosynthetic clay liners (NP GCLs) under monotonic loading. A new dynamic direct Shear apparatus with the capability to cover a large range of normal stress and displacement rate is developed. Series of direct Shear tests on NP GCL for different normal stress levels and displacement rates are performed. The failure mechanism of hydrated GCL is explored through inspection of tested specimens and analysis of test results. The intrinsic relationship between peak/residual Shear strength of NP GCL and displacement rate is also studied. Experimental results indicated that displacement rate has obvious effect on the peak Shear strength of NP GCL, while the influence of displacement rate on residual Shear strength is of little significance for the same normal stress level.

Hisham T Eid - One of the best experts on this subject based on the ideXlab platform.

  • Shear strength of geosynthetic composite systems for design of landfill liner and cover slopes
    Geotextiles and Geomembranes, 2011
    Co-Authors: Hisham T Eid
    Abstract:

    Abstract Torsional ring Shear tests were performed on composite specimens that simulate the field alignment of municipal solid waste (MSW) landfill liner and cover system components. Simultaneous Shearing was provided to each test specimen without forcing failure to occur through a pre-determined plane. Composite liner specimens consisted of a textured geomembrane (GM) underlain by a needle-punched geosynthetic clay liner (GCL) which in turn underlain by a compacted silty clay. Hydrated specimens were Sheared at eleven different normal stress levels. Test results revealed that Shear strength of the composite liner system can be controlled by different failure modes depending on the magnitude of normal stress and the comparative values of the GCL interface and Internal Shear strength. Failure following these modes may result in a bilinear or trilinear peak strength envelope and a corresponding stepped residual strength envelope. Composite cover specimens that comprised textured GM placed on unreinforced smooth GM-backed GCL resting on compacted sand were Sheared at five different GCL hydration conditions and a normal stress that is usually imposed on MSW landfill cover geosynthetic components. Test results showed that increasing the GCL hydration moves the Shearing plane from the GCL smooth GM backing/sand interface to that of the textured GM/hydrated bentonite. Effects of these interactive Shear strength behaviors of composite liner and cover system components on the possibility of developing progressive failure in landfill slopes were discussed. Recommendations for designing landfill geosynthetic-lined slopes were subsequently given. Three-dimensional stability analysis of well-documented case history of failed composite system slope was presented to support the introduced results and recommendations.

  • effect of Shear displacement rate on Internal Shear strength of a reinforced geosynthetic clay liner
    Geosynthetics International, 1999
    Co-Authors: Hisham T Eid, C K Doerfler
    Abstract:

    Torsional ring Shear tests were performed to evaluate the effect of Shear displacement rate on the Internal Shear strength of a needle-punched geosynthetic clay liner (GCL) under different normal stresses. The test results suggest that the Internal Shear strength of the needle-punched GCL depends on the following three factors: (i) resistance against reinforcement fibers pulling out and/or tearing; (ii) amount of positive pore-water pressure induced during Shear; and (iii) bentonite water content at the time of Shearing. The laboratory tests indicate that the net effect of these three factors result in the peak Internal Shear strength being less sensitive to Shear displacement rate at normal stresses between 200 and 400 kPa than at normal stresses less than 200 kPa. Shear displacement rate appears to have little influence on the residual Internal Shear strength regardless of normal stress. The amount of Shear displacement required to reach the peak and residual Internal Shear strengths is dependent on the...

Shijin Feng - One of the best experts on this subject based on the ideXlab platform.

  • Shear strength and failure mechanism of needle punched geosynthetic clay liner
    Geotextiles and Geomembranes, 2020
    Co-Authors: Shijin Feng, Jiyun Chang, Yang Shen, Hongxin Chen, Jialiang Shi
    Abstract:

    Abstract The Internal Shear strength of a geosynthetic clay liner (GCL) within composite liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the Shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct Shear tests with five normal stress levels (250–1000 kPa) and eight displacement rates (1–200 mm/min) were conducted. The Shear stress to horizontal displacement relationships exhibit well-defined peak Shear strengths and significant post-peak strength reductions. The monitoring results of the thickness change indicate that the degree of volumetric contraction is related to the reorientation of fibers and dissipation of pore water pressure. Furthermore, the peak and residual Shear strengths both depend on the displacement rate because of the rate-dependent tensile stiffness of needle-punched fibers and Shear strength of the soil/geosynthetic interface. Through additional tests and lateral comparison, it was discovered that the Shear behavior of sodium bentonite, degree of hydration, and pore water pressures all affect the Shear mechanisms of the NP GCL. In particular, the failure mode transfers from fiber pullout to fiber rupture with the increase in water content as the hydrated bentonite particles facilitate the stretching of needle-punched fibers.

  • experimental study of Shear strength of geosynthetic clay liner for monotonic loading
    The International Congress on Environmental Geotechnics, 2018
    Co-Authors: Jiyun Chang, Shijin Feng, Yang Shen, Hao Shi, Jialiang Shi
    Abstract:

    Internal Shear strength of geosynthetic clay liner (GCL) is of vital importance for the stability of waste containment facilities where GCLs are widely used as hydraulic barriers. This paper presents an experimental investigation of the Internal Shear strength of hydrated needle-punched geosynthetic clay liners (NP GCLs) under monotonic loading. A new dynamic direct Shear apparatus with the capability to cover a large range of normal stress and displacement rate is developed. Series of direct Shear tests on NP GCL for different normal stress levels and displacement rates are performed. The failure mechanism of hydrated GCL is explored through inspection of tested specimens and analysis of test results. The intrinsic relationship between peak/residual Shear strength of NP GCL and displacement rate is also studied. Experimental results indicated that displacement rate has obvious effect on the peak Shear strength of NP GCL, while the influence of displacement rate on residual Shear strength is of little significance for the same normal stress level.

Anthony L Piro - One of the best experts on this subject based on the ideXlab platform.

  • the Internal Shear of type ia supernova progenitors during accretion and simmering
    The Astrophysical Journal, 2008
    Co-Authors: Anthony L Piro
    Abstract:

    A white dwarf (WD) gains substantial angular momentum during the accretion process that grows it toward a Chandrasekhar mass. It is therefore expected to be rotating quickly when it ignites as a Type Ia supernova. The thermal and Shearing profiles are important for subsequent flame propagation. We highlight processes that could affect the WD Shear during accretion, as well as during the ~1000 yr of pre-explosive simmering. Baroclinic instabilities and/or the Shear growth of small magnetic fields provide sufficient torque to bring the WD very close to solid-body rotation during accretion. The lack of significant Shear makes it difficult to grow a WD substantially past the typical Chandrasekhar mass. Once carbon ignites, a convective region spreads from the center of the WD. This phase occurs regardless of progenitor scenario, and therefore it is of great interest for understanding how the WD interior is prepared before the explosive burning begins. We summarize some of the key properties of the convective region, including a demonstration that the mass enclosed by convection at any given time depends most sensitively on a single parameter that can be expressed as either the ratio of temperatures or densities at the top and bottom of the convection zone. At low Rossby numbers, the redistribution of angular momentum by convection may result in significant Shearing at the convective/nonconvective boundary.

  • the Internal Shear of type ia supernova progenitors during accretion and simmering
    arXiv: Astrophysics, 2008
    Co-Authors: Anthony L Piro
    Abstract:

    A white dwarf (WD) gains substantial angular momentum during the accretion process that grows it toward a Chandrasekhar mass. It is therefore expected to be quickly rotating when it ignites as a Type Ia supernova. The thermal and Shearing profile are important for subsequent flame propagation. We highlight processes that could affect the WD Shear, during accretion as well as during the ~1000 years of pre-explosive simmering. Baroclinic instabilities and/or the Shear growth of small magnetic fields provide sufficient torque to bring the WD very close to solid body rotation during accretion. The lack of significant Shear makes it difficult to grow a WD substantially past the typical Chandrasekhar mass. Once carbon ignites, a convective region spreads from the WD's center. This phase occurs regardless of progenitor scenario, and therefore it is of great interest for understanding how the WD interior is prepared before the explosive burning begins. We summarize some of the key properties of the convective region, which includes demonstrating that the mass enclosed by convection at any given time depends most sensitively on a single parameter that can be expressed as either the ratio of temperatures or densities at the top and bottom of the convection zone. At low Rossby numbers the redistribution of angular momentum by convection may result in significant Shearing at the convective/non-convective boundary.

Louiss Bouchard - One of the best experts on this subject based on the ideXlab platform.

  • macro scale topology optimization for controlling Internal Shear stress in a porous scaffold bioreactor
    Biotechnology and Bioengineering, 2012
    Co-Authors: Khalid Youssef, Julia J Mack, M L Iruelaarispe, Louiss Bouchard
    Abstract:

    Shear stress is an important physical factor that regulates proliferation, migration, and morphogenesis. In particular, the homeostasis of blood vessels is dependent on Shear stress. To mimic this process ex vivo, efforts have been made to seed scaffolds with vascular and other cell types in the presence of growth factors and under pulsatile flow conditions. However, the resulting bioreactors lack information on Shear stress and flow distributions within the scaffold. Consequently, it is difficult to interpret the effects of Shear stress on cell function. Such knowledge would enable researchers to improve upon cell culture protocols. Recent work has focused on optimizing the microstructural parameters of the scaffold to fine tune the Shear stress. In this study, we have adopted a different approach whereby flows are redirected throughout the bioreactor along channels patterned in the porous scaffold to yield Shear stress distributions that are optimized for uniformity centered on a target value. A topology optimization algorithm coupled to computational fluid dynamics simulations was devised to this end. The channel topology in the porous scaffold was varied using a combination of genetic algorithm and fuzzy logic. The method is validated by experiments using magnetic resonance imaging readouts of the flow field. Biotechnol. Bioeng. 2012; 109:1844–1854. © 2012 Wiley Periodicals, Inc.

  • macro scale topology optimization for controlling Internal Shear stress in a porous scaffold bioreactor
    arXiv: Soft Condensed Matter, 2011
    Co-Authors: Khalid Youssef, Julia J Mack, M L Iruelaarispe, Louiss Bouchard
    Abstract:

    Shear stress is an important physical factor that regulates proliferation, migration and morphogenesis. In particular, the homeostasis of blood vessels is dependent on Shear stress. To mimic this process ex vivo, efforts have been made to seed scaffolds with vascular and other cell types in the presence of growth factors and under pulsatile flow conditions. However, the resulting bioreactors lack information on Shear stress and flow distributions within the scaffold. Consequently, it is difficult to interpret the effects of Shear stress on cell function. Such knowledge would enable researchers to improve upon cell culture protocols. Recent work has focused on optimizing the microstructural parameters of the scaffold to fine tune the Shear stress. In this study, we have adopted a different approach whereby flows are redirected throughout the bioreactor along channels patterned in the porous scaffold to yield Shear stress distributions that are optimized for uniformity centered on a target value. A topology optimization algorithm coupled to computational fluid dynamics simulations was devised to this end. The channel topology in the porous scaffold was varied using a combination of genetic algorithm and fuzzy logic. The method is validated by experiments using magnetic resonance imaging (MRI) readouts of the flow field.