“…However, a higher dilative tendency for SS was observed with 0.5% FM. This turnover is likely due to the larger D 50 of the OS samples, given that similar results have been reported by Michalowski and Cermak ( 2002 ), Ghadr and Assadi-langroudi ( 2019 ), and Ghadr and Bahadori ( 2019 ). Fig.…”
Section: Resultssupporting
confidence: 82%
“…Interestingly, a more significant gain in q 20 is observed in the FM-reinforced OS (sharper increment) than the FM-reinforced SS (milder increment). Smiliar observation was made by Maher and Gray ( 1990 ), Michalowski and Cermak ( 2002 ), Ghadr and Bahadori ( 2019 ), and Ghadr ( 2020 ), who stated that the strengthening effect of the fiber (for a given FM content in this study) can decrease in sands with larger D 50 . Lastly, it is evident that 0.3% FM content, regardless of the FM lengths and effective mean stresses, is generally associated with the higher q 20 , specifically for OS.…”
Section: Resultssupporting
confidence: 68%
“…Numerous studies have demonstrated that mixing sand with fibers can effectively improve the mechanical performance of the latter. The tensile strength of the fibers intersecting the shear failure surface in the sand increases the shear strength of the sand (Consoli et al 2002 ; Velloso et al 2012 ; Sotomayor and Casagrande 2018 ; Louzada et al 2019 ; Ghadr and Bahadori 2019 ; Correia et al 2021 ). Previous studies also showed that the reinforcement type, length, aspect ratio, content, and particle size affect reinforcement effectiveness (Ibraim et al 2010 ; Michalowski and Cermak 2002 ; Ghadr and Bahadori 2019 ; Ghadr 2020 ).…”
Section: Introductionmentioning
confidence: 99%
“…The tensile strength of the fibers intersecting the shear failure surface in the sand increases the shear strength of the sand (Consoli et al 2002 ; Velloso et al 2012 ; Sotomayor and Casagrande 2018 ; Louzada et al 2019 ; Ghadr and Bahadori 2019 ; Correia et al 2021 ). Previous studies also showed that the reinforcement type, length, aspect ratio, content, and particle size affect reinforcement effectiveness (Ibraim et al 2010 ; Michalowski and Cermak 2002 ; Ghadr and Bahadori 2019 ; Ghadr 2020 ). Zornberg et al ( 2004 ) reported that soil mixed with waste tire shreds can be used as an alternative backfill material to solve low soil shear strength problems, and Li et al ( 2016 ) showed that using tire wastes can improve soil performance.…”
The rapid response to the COVID-19 pandemic has resulted in increased municipal waste in the form of used face masks (FMs), which pose a global threat to the environment. To mitigate this, the study explores the applicability of shredded FMs as alternative reinforcing material in sands. Laboratory-grade Ottawa sand and naturally collected sea sand are adopted as the base sands for testing. The primary physical properties of the base materials and the FMs are first examined, and the soil particles are imaged via scanning electron microscopy. Thirty consolidated undrained (CU) triaxial compression tests were conducted to evaluate the effects of the weight fraction of FM, FM length, and the initial effective mean stress on the undrained shear strength parameters of the sands. The experimental results proved that FM inclusion can lead to a substantial improvement in the undrained shear strength of the sands; however, such improvement was sensitive to the initial effective mean stress, with higher undrained shear strength gains associated with lower initial effective mean stress. For a given FM content, the critical state ratio and angle of friction at the critical state increased with the FM length. Finally, the results revealed that FM-reinforced sands exhibit dilative and strain-hardening behaviors.
“…However, a higher dilative tendency for SS was observed with 0.5% FM. This turnover is likely due to the larger D 50 of the OS samples, given that similar results have been reported by Michalowski and Cermak ( 2002 ), Ghadr and Assadi-langroudi ( 2019 ), and Ghadr and Bahadori ( 2019 ). Fig.…”
Section: Resultssupporting
confidence: 82%
“…Interestingly, a more significant gain in q 20 is observed in the FM-reinforced OS (sharper increment) than the FM-reinforced SS (milder increment). Smiliar observation was made by Maher and Gray ( 1990 ), Michalowski and Cermak ( 2002 ), Ghadr and Bahadori ( 2019 ), and Ghadr ( 2020 ), who stated that the strengthening effect of the fiber (for a given FM content in this study) can decrease in sands with larger D 50 . Lastly, it is evident that 0.3% FM content, regardless of the FM lengths and effective mean stresses, is generally associated with the higher q 20 , specifically for OS.…”
Section: Resultssupporting
confidence: 68%
“…Numerous studies have demonstrated that mixing sand with fibers can effectively improve the mechanical performance of the latter. The tensile strength of the fibers intersecting the shear failure surface in the sand increases the shear strength of the sand (Consoli et al 2002 ; Velloso et al 2012 ; Sotomayor and Casagrande 2018 ; Louzada et al 2019 ; Ghadr and Bahadori 2019 ; Correia et al 2021 ). Previous studies also showed that the reinforcement type, length, aspect ratio, content, and particle size affect reinforcement effectiveness (Ibraim et al 2010 ; Michalowski and Cermak 2002 ; Ghadr and Bahadori 2019 ; Ghadr 2020 ).…”
Section: Introductionmentioning
confidence: 99%
“…The tensile strength of the fibers intersecting the shear failure surface in the sand increases the shear strength of the sand (Consoli et al 2002 ; Velloso et al 2012 ; Sotomayor and Casagrande 2018 ; Louzada et al 2019 ; Ghadr and Bahadori 2019 ; Correia et al 2021 ). Previous studies also showed that the reinforcement type, length, aspect ratio, content, and particle size affect reinforcement effectiveness (Ibraim et al 2010 ; Michalowski and Cermak 2002 ; Ghadr and Bahadori 2019 ; Ghadr 2020 ). Zornberg et al ( 2004 ) reported that soil mixed with waste tire shreds can be used as an alternative backfill material to solve low soil shear strength problems, and Li et al ( 2016 ) showed that using tire wastes can improve soil performance.…”
The rapid response to the COVID-19 pandemic has resulted in increased municipal waste in the form of used face masks (FMs), which pose a global threat to the environment. To mitigate this, the study explores the applicability of shredded FMs as alternative reinforcing material in sands. Laboratory-grade Ottawa sand and naturally collected sea sand are adopted as the base sands for testing. The primary physical properties of the base materials and the FMs are first examined, and the soil particles are imaged via scanning electron microscopy. Thirty consolidated undrained (CU) triaxial compression tests were conducted to evaluate the effects of the weight fraction of FM, FM length, and the initial effective mean stress on the undrained shear strength parameters of the sands. The experimental results proved that FM inclusion can lead to a substantial improvement in the undrained shear strength of the sands; however, such improvement was sensitive to the initial effective mean stress, with higher undrained shear strength gains associated with lower initial effective mean stress. For a given FM content, the critical state ratio and angle of friction at the critical state increased with the FM length. Finally, the results revealed that FM-reinforced sands exhibit dilative and strain-hardening behaviors.
“…The strength anisotropy of fibre-reinforced sand was recently illustrated by performing the hollow cylinder torsional shear (HCTS) tests. The strength of fibre-reinforced sand is largely affected by the direction of the major principal stress [40][41][42]. Roughly, a rise in inclination angle of the major principal stress with respect to the deposition direction, which is usually horizontal, causes a reduction in strength.…”
Adding discrete fibres to sand has been seen as a feasible technique to improve sand’s strength as well as liquefaction resistance. Considering the anisotropic distribution of fibre orientations, the anisotropy in the liquefaction resistance of the reinforced sand is also introduced using fibres. Here, the triaxial compression and extension test results of unreinforced and fibre-reinforced sand in different density states are provided, from which the anisotropy in the liquefaction resistance of fibre-reinforced sand is demonstrated. Fibre reinforcement improves the liquefaction resistance of sand by introducing both the densifying effect and the confining effect. The inclusion of fibres increases both the slope and the intercept of the strength envelope in comparison with the unreinforced sand under triaxial compression, while the strength envelope is not affected by fibres under triaxial extension. Stress contribution of fibres makes the ESP of the composite under undrained loading reverse its direction to develop even though the phase transformation is absent. The stress ratio initiating the ESP reversal is irrespective of the fibre content but dependent on the density state under triaxial compression. Under triaxial extension, the stress ratio initiating the ESP reversal remains the same in the samples with varied density states and fibre contents. The mechanism correlating to the strength envelope and ESP reversal of the fibre-reinforced sand was demonstrated following a rule of mixture based constitutive modelling framework. By introducing an alternatively defined pore pressure ratio that incorporates the stress contribution of fibres, the liquefaction state of the fibre reinforced sand is reasonably assessed. Liquefaction remains absent in the sand once the fibres are mixed. The anisotropy in the liquefaction resistance of fibre-reinforced sand arises, as the predominant role played by the fibres to suppress the liquefaction is different when varied loading paths are involved, which is sourced from the anisotropic distribution of fibre orientations.
The influence of polypropylene fiber inclusion on the wave propagation parameters and stiffness anisotropy of granular materials was examined through vertically and laterally positioned bender elements, by which, shear wave velocities were measured leading to the quantification of elastic stiffness Gmax(vh), Gmax(hv) and Gmax(hh) (the first subscript corresponds to the direction of wave propagation and the second subscript corresponds to the direction of particle perturbation as v:vertical and h:horizontal). Various stress paths were considered to comprehensively study stiffness anisotropy of the specimens and grain-scale laboratory tests were additionally performed to provide, partly, some multi-scale insights into the mechanisms of wave propagation of the sandfiber granular composites. For the back-calculation of elastic stiffness from the wave propagation experiments, Biot's theory was adopted, in which case an equivalent density was used to interpret the high-frequency test results taking into account the relative movement of the solid and fluid phases, which approach provided much better convergency of the results from bender elements and resonant column tests. In this case we assumed that the solid skeleton is composed of the sand particles and the fibers. The test results indicated that when subjected to isotropic stress state, the presence of fibers led to a decrease of Gmax(vh) and Gmax(hv) but an increase of Gmax(hh). The extent of Gmax(hh) increase was dependent on the characteristics of the host sand and could be attributed to the structural anisotropy with preferred horizontal orientation of the fibers leading to more pronounced development of rigid-soft contacts in the vertical direction. The contribution of the rigid-soft contacts in stiffness reduction could be linked to the microscopic influence of the softer synthetic fibers in reducing the normal contact stiffness and increasing the energy dissipation of the granular system as the grain-scale experiments suggested. When subjected to anisotropic stress state, the stiffness anisotropy was affected by fiber content in a way that with increasing amount of fiber inclusion, the reduction of the stiffness anisotropy became larger. The stiffness anisotropy of the sand or sand-fiber binary system increased with the increase of the stress ratio. Further analysis of the test results revealed that stress induced anisotropy was directly linked to the influence of deviatoric stress on the volumetric strain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
