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Nicola Moraci - One of the best experts on this subject based on the ideXlab platform.
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A Predictive Model for Pullout Bearing Resistance of Geogrids Embedded in a Granular Soil
Geotechnical Research for Land Protection and Development, 2020Co-Authors: Giuseppe Cardile, Marina Pisano, Nicola MoraciAbstract:Currently, Geosynthetic-Reinforced Soil (GRS) structures represent one of the most sustainable solutions capable to improve the protection of the territory, guaranteeing high performance (especially in seismic field) with construction costs that are lower than those required for the more traditional Civil and Environmental engineering works. To design such types of structures the knowledge of Soil-geosynthetic interface parameters is necessary, and their prediction is very complex due to the elementary interaction mechanisms affecting the pullout resistance of geogrids embedded in Soils that are mainly the skin friction between Soil and the reinforcement’s solid surface, and the bearing resistance developing on transverse elements. When the spacing between the geogrid’s transverse elements is below a threshold value, the interference mechanism develops and it can affect the bearing resistance, as the passive surfaces cannot be entirely mobilised on bearing members. In order to model the peak pullout resistance of extruded geogrids embedded in a compacted Granular Soil, the paper deals with a new experimental validation of a theoretical method taking into account the interference mechanism.
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deformative behaviour of different geogrids embedded in a Granular Soil under monotonic and cyclic pullout loads
Geotextiles and Geomembranes, 2012Co-Authors: Nicola Moraci, Giuseppe CardileAbstract:Abstract This paper deals with the results of a wide experimental research carried out in order to study factors affecting the cyclic and post-cyclic pullout behaviour of different geogrids embedded in a compacted Granular Soil. In a previous paper ( Moraci and Cardile, 2009 ) the influence of the tensile cyclic load frequency and amplitude, vertical confining stress and geogrids structure on the pullout resistance and on the interface apparent coefficient of friction was studied. In this paper, the influence of the same factors on the pullout behaviour in terms of accumulated displacements and deformations are analysed.
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influence of cyclic tensile loading on pullout resistance of geogrids embedded in a compacted Granular Soil
Geotextiles and Geomembranes, 2009Co-Authors: Nicola Moraci, Giuseppe CardileAbstract:Abstract This paper deals with some results of a wide experimental research carried out in order to study factors affecting cyclic and post-cyclic pullout behaviour of different geogrids embedded in a Granular Soil. The new test procedure developed (multistage pullout test) and the relative results are described. In particular, test results obtained using the constant rate of displacement (CRD) and the multistage pullout tests highlighted the influence of the different factors involved in the research (cyclic load amplitude and frequency, vertical confining stress, geogrid tensile stiffness and structure) both on the peak pullout resistance and on the peak apparent coefficient of friction mobilized at the interface.
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factors affecting the pullout behaviour of extruded geogrids embedded in a compacted Granular Soil
Geotextiles and Geomembranes, 2006Co-Authors: Nicola Moraci, Piergiorgio RecalcatiAbstract:Abstract In order to study the factors affecting the behaviour of reinforcement geogrids embedded in Granular compacted Soils, a large-scale pullout test apparatus has been designed. More than 40 pullout tests have been performed, at constant displacement rate, on three different HDPE extruded geogrids embedded in a compacted Granular Soil by varying the specimen lengths and the applied vertical effective pressures. The different geogrids used in the research have been tested using unconfined tensile tests performed at different speeds, and, in particular, at the same speed of the pullout tests; Granular Soil have been characterized through classification, Proctor and shear tests. The pullout test results showed the influence of the different parameters studied on pullout behaviour. Moreover, on the basis of the test results it was possible to evaluate the peak and the residual pullout resistance and the apparent coefficient of friction mobilized in the same conditions.
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a simple method to evaluate the pullout resistance of extruded geogrids embedded in a compacted Granular Soil
Geotextiles and Geomembranes, 2006Co-Authors: Nicola Moraci, Domenico GioffreAbstract:Abstract Pullout tests are necessary in order to study the interaction behaviour between Soil and geosynthetics in the anchorage zone; hence, the resulting properties have direct implications on the design of reinforced Soil structures. Several experimental studies showed the influence of different parameters (reinforcement stiffness, geometry and length, applied vertical effective stress, and geotechnical properties of Soil) on the peak and on residual pullout resistance. On the basis of the results of the tests carried out by Moraci and Recalcati [2005. Factors affecting the pullout behaviour of extruded geogrids embedded in a compacted Granular Soil. Geotextiles and Geomembranes, submitted for publication], a new theoretical method was developed to determine the peak and the residual pullout resistance of extruded geogrids embedded in a compacted Granular Soil. The method is capable of evaluating both the bearing and the frictional components of pullout resistance, taking into account the reinforcement extensibility and geometry as well as the non-linearity of the failure envelope of backfill Soil. The comparison between theoretical and experimental results was favourable, thus confirming the suitability of the proposed approach.
Giuseppe Cardile - One of the best experts on this subject based on the ideXlab platform.
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A Predictive Model for Pullout Bearing Resistance of Geogrids Embedded in a Granular Soil
Geotechnical Research for Land Protection and Development, 2020Co-Authors: Giuseppe Cardile, Marina Pisano, Nicola MoraciAbstract:Currently, Geosynthetic-Reinforced Soil (GRS) structures represent one of the most sustainable solutions capable to improve the protection of the territory, guaranteeing high performance (especially in seismic field) with construction costs that are lower than those required for the more traditional Civil and Environmental engineering works. To design such types of structures the knowledge of Soil-geosynthetic interface parameters is necessary, and their prediction is very complex due to the elementary interaction mechanisms affecting the pullout resistance of geogrids embedded in Soils that are mainly the skin friction between Soil and the reinforcement’s solid surface, and the bearing resistance developing on transverse elements. When the spacing between the geogrid’s transverse elements is below a threshold value, the interference mechanism develops and it can affect the bearing resistance, as the passive surfaces cannot be entirely mobilised on bearing members. In order to model the peak pullout resistance of extruded geogrids embedded in a compacted Granular Soil, the paper deals with a new experimental validation of a theoretical method taking into account the interference mechanism.
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deformative behaviour of different geogrids embedded in a Granular Soil under monotonic and cyclic pullout loads
Geotextiles and Geomembranes, 2012Co-Authors: Nicola Moraci, Giuseppe CardileAbstract:Abstract This paper deals with the results of a wide experimental research carried out in order to study factors affecting the cyclic and post-cyclic pullout behaviour of different geogrids embedded in a compacted Granular Soil. In a previous paper ( Moraci and Cardile, 2009 ) the influence of the tensile cyclic load frequency and amplitude, vertical confining stress and geogrids structure on the pullout resistance and on the interface apparent coefficient of friction was studied. In this paper, the influence of the same factors on the pullout behaviour in terms of accumulated displacements and deformations are analysed.
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influence of cyclic tensile loading on pullout resistance of geogrids embedded in a compacted Granular Soil
Geotextiles and Geomembranes, 2009Co-Authors: Nicola Moraci, Giuseppe CardileAbstract:Abstract This paper deals with some results of a wide experimental research carried out in order to study factors affecting cyclic and post-cyclic pullout behaviour of different geogrids embedded in a Granular Soil. The new test procedure developed (multistage pullout test) and the relative results are described. In particular, test results obtained using the constant rate of displacement (CRD) and the multistage pullout tests highlighted the influence of the different factors involved in the research (cyclic load amplitude and frequency, vertical confining stress, geogrid tensile stiffness and structure) both on the peak pullout resistance and on the peak apparent coefficient of friction mobilized at the interface.
Xiaodong Luo - One of the best experts on this subject based on the ideXlab platform.
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dem investigation on the effect of sample preparation on the shear behavior of Granular Soil
Particuology, 2016Co-Authors: Beibing Dai, Jun Yang, Cuiying Zhou, Xiaodong LuoAbstract:Abstract The effect of initial fabric anisotropy produced by sample preparation on the shear behavior of Granular Soil is investigated by performing discrete element method (DEM) simulations of fourteen biaxial tests in drained conditions. Numerical test specimens are prepared by three means: gravitational deposition, multi-layer compression, and isotropic compression, such that different initial inherent Soil fabrics are created. The DEM simulation results show that initial fabric anisotropy exerts a considerable effect on the shear behavior of Granular Soil, and that the peak stress ratio and peak dilatancy increase with an increase in the fabric index a n that is estimated from the contact orientations. The stress–dilatancy relationship is found to be independent of the initial fabric anisotropy. The anisotropy related to the contact orientation and contact normal force accounts for the main contribution to the mobilized friction angle. Also, the occurrence of contractive shear response in an initial shearing stage is accompanied by the most intense particle rearrangement and microstructural reorganization, regardless of the sample preparation method. Furthermore, the uniqueness of the critical state line in e –log p ′ and q–p ′ plots is observed, suggesting that the influence of initial fabric anisotropy is erased at large shear strains.
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a numerical analysis of the shear behavior of Granular Soil with fines
Particuology, 2015Co-Authors: Beibing Dai, Jun Yang, Xiaodong LuoAbstract:Abstract Shear behavior of Granular Soil with fines is investigated using the discrete element method (DEM) and particle arrangements and inter-particle contacts during shear are examined. The DEM simulation reveals that fine particles play a vital role in the overall response of Granular Soil to shearing. The occurrence of liquefaction and temporary reduction of strength is ascribed mainly to the loss of support from the fine particle contacts (S–S) and fine particle-to-large particle contacts (S–L) as a consequence of the removal of fine particles from the load-carrying skeleton. The dilative strain-hardening response following the strain-softening response is associated with the migration of fine particles back into the load-carrying skeleton, which is thought to enhance the stiffness of the Soil skeleton. During shear, the unit normal vector of the large particle-to-large particle (L–L) contact has the strongest fabric anisotropy, and the S–S contact unit normal vector possesses the weakest anisotropy, suggesting that the large particles play a dominant role in carrying the shear load. It is also found that, during shear, fine particles are prone to rolling at contacts while the large particles are prone to sliding, mainly at the S–L and L–L contacts.
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A numerical analysis of the shear behavior of Granular Soil with fines
Particuology, 2015Co-Authors: Beibing Dai, Jun Yang, Xiaodong LuoAbstract:Shear behavior of Granular Soil with fines is investigated using the discrete element method (DEM) and particle arrangements and inter-particle contacts during shear are examined. The DEM simulation reveals that fine particles play a vital role in the overall response of Granular Soil to shearing. The occurrence of liquefaction and temporary reduction of strength is ascribed mainly to the loss of support from the fine particle contacts (S-S) and fine particle-to-large particle contacts (S-L) as a consequence of the removal of fine particles from the load-carrying skeleton. The dilative strain-hardening response following the strain-softening response is associated with the migration of fine particles back into the load-carrying skeleton, which is thought to enhance the stiffness of the Soil skeleton. During shear, the unit normal vector of the large particle-to-large particle (L-L) contact has the strongest fabric anisotropy, and the S-S contact unit normal vector possesses the weakest anisotropy, suggesting that the large particles play a dominant role in carrying the shear load. It is also found that, during shear, fine particles are prone to rolling at contacts while the large particles are prone to sliding, mainly at the S-L and L-L contacts. © 2015 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy ofSciences. Published by Elsevier B.V. All rights reserved
Richard J Bathurst - One of the best experts on this subject based on the ideXlab platform.
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insights into geogrid Soil interaction using a transparent Granular Soil
Geotechnique Letters, 2017Co-Authors: Richard J Bathurst, Fawzy M EzzeinAbstract:Geogrid pullout tests were carried out in a large pullout box filled with a transparent Granular Soil. Geogrid displacements and displacements of a dispersed layer of opaque particles located immediately above and below the plane of the geogrid were measured from image analysis of pictures taken through a window at the bottom of the box. Longitudinal displacements of an extensible biaxial polypropylene geogrid were converted to strains and strain rates and these values used in a rate-dependent load–strain model to calculate load along the entire length of the specimen and load transfer to the surrounding Soil. Plots of load transfer, expressed as equivalent shear stress acting over the area between transverse members, against relative horizontal deformation between the geogrid inclusion and the surrounding Soil were generated. These data show that for the combination of geogrid and Granular Soil used in this investigation, load transfer is largely due to shear between the Soil particles trapped in the pla...
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geogrid pullout load strain behaviour and modelling using a transparent Granular Soil
Geosynthetics International, 2016Co-Authors: Richard J Bathurst, Fawzy M EzzeinAbstract:The paper describes the results of a series of geogrid pullout tests that were carried out in a novel large pullout box with a transparent Granular Soil. The test apparatus and methodology allows the entire geogrid specimen to be visible through the bottom of the box. Specimen displacements are computed from image analysis of pictures taken through the transparent bottom of the pullout box during each test. The geogrid material was an integral punched and drawn biaxial polypropylene geogrid. A series of reference tests were carried out on geogrid specimens 2000 mm long and loaded at a front clamp displacement of 1 mm/min. The results of these tests have been reported in previous publication by the writers. In the current study, this earlier database of test results and interpretation of results is extended to include tests with specimens of different (shorter) length and loaded at other displacement rates. The tensile loads in the specimens are estimated using two different nonlinear rate-dependent load–s...
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geogrid and Soil displacement observations during pullout using a transparent Granular Soil
Geotechnical Testing Journal, 2015Co-Authors: Richard J Bathurst, Fawzy M EzzeinAbstract:Current practice to quantify the load transfer capacity between Soil and geosynthetic reinforcement materials in the anchorage zone of a wall, slope, or embankment is to carryout laboratory pullout tests. In a recent paper, the authors described a novel large pullout box with a transparent bottom. Geogrid specimens up to 2000 mm in length were embedded in a transparent fused quartz Soil and the specimens subjected to constant rate-of-displacement in-air testing and in-Soil pullout testing under a range of normal stress. Displacement–time histories over the entire area of each reinforcement specimen were measured using the digital image correlation (DIC) technique applied to sequential images captured by a row of cameras located directly below the test apparatus. Opaque particles were also mixed with the transparent Soil particles so that horizontal displacement of the Soil in the planes immediately above and below the geogrid specimens could be tracked. The difference in horizontal displacement response corresponds to the relative shear displacement between the Soil and geogrid that is responsible for load transfer during pullout. These results demonstrate the utility of the experimental methodology using the transparent fused quartz material as a successful analog to a natural sand Soil for the investigation of Granular Soil–geogrid interaction. The example data is a necessary precursor to the development of interface shear models for load transfer in the anchorage zone of geogrid reinforced Soil structures.
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a new approach to evaluate Soil geosynthetic interaction using a novel pullout test apparatus and transparent Granular Soil
Geotextiles and Geomembranes, 2014Co-Authors: Fawzy M Ezzein, Richard J BathurstAbstract:Abstract Geosynthetic reinforced Soil walls and slopes are now a mature technology in geotechnical engineering. Nevertheless, the mechanisms of Soil-geosynthetic interaction are not fully understood for pullout of a geogrid material in the anchorage zone of a reinforced structure. It is also difficult to quantify the interactions between the geogrid and the Soil. A new strategy to overcome these difficulties is to use a pullout box with a transparent glass bottom, a transparent Soil, and non-contact measurement technology. This paper describes such a pullout box apparatus which is used in combination with a recently developed transparent Granular Soil. Embedded geogrid specimens are visible through the transparent bottom of the box and the surrounding Soil. The displacements of the geogrid and seed (target) particles placed in the transparent Soil are tracked using digital images captured by a row of synchronized cameras located below the apparatus. Digital processing is carried out using the Digital Image Correlation (DIC) technique to quantify the in-situ displacement of the geogrid specimen and surrounding Soil. The displacements are used to compute continuous longitudinal strain profiles in the geogrid specimen over the duration of each pullout test and relative shear displacements between the geogrid and the Soil. Also reported are lessons learned to improve the method of clamping geogrid specimens at the front of the pullout box which are also applicable to conventional pullout box equipment.
Jun Yang - One of the best experts on this subject based on the ideXlab platform.
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small strain shear modulus of volcanic Granular Soil an experimental investigation
Soil Dynamics and Earthquake Engineering, 2016Co-Authors: Xin Liu, Jun Yang, Gonghui Wang, Longzhu ChenAbstract:While volcanic Soils exist in many places around the world, their mechanical behavior is however less extensively studied as compared to the conventional Soil type such as quartz sand and clay. This paper presents an experimental study investigating the small-strain shear modulus (G0) and associated shear wave velocity (Vs) of a volcanic Granular Soil collected from the northeast of Japan that was affected by the devastating 2011 Tohoku earthquake. Reconstituted Soil specimens were tested at different packing densities and confining stress levels by using the resonant column technique, and the pressure and density dependence of shear modulus was established for the Soil. The study showed that under otherwise similar conditions, the G0 value of the volcanic Soil was markedly lower than that of clean quartz sands, but it tended to increase significantly when the fine particles in the Soil were removed. This finding suggests that the presence of fines plays an important role in the mechanical behavior of volcanic Soils. A practical model accounting for the influence of fines and the pressure and density dependence is proposed and it is shown to provide reasonable estimates of G0 for both volcanic Soils and clean quartz sands studied.
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dem investigation on the effect of sample preparation on the shear behavior of Granular Soil
Particuology, 2016Co-Authors: Beibing Dai, Jun Yang, Cuiying Zhou, Xiaodong LuoAbstract:Abstract The effect of initial fabric anisotropy produced by sample preparation on the shear behavior of Granular Soil is investigated by performing discrete element method (DEM) simulations of fourteen biaxial tests in drained conditions. Numerical test specimens are prepared by three means: gravitational deposition, multi-layer compression, and isotropic compression, such that different initial inherent Soil fabrics are created. The DEM simulation results show that initial fabric anisotropy exerts a considerable effect on the shear behavior of Granular Soil, and that the peak stress ratio and peak dilatancy increase with an increase in the fabric index a n that is estimated from the contact orientations. The stress–dilatancy relationship is found to be independent of the initial fabric anisotropy. The anisotropy related to the contact orientation and contact normal force accounts for the main contribution to the mobilized friction angle. Also, the occurrence of contractive shear response in an initial shearing stage is accompanied by the most intense particle rearrangement and microstructural reorganization, regardless of the sample preparation method. Furthermore, the uniqueness of the critical state line in e –log p ′ and q–p ′ plots is observed, suggesting that the influence of initial fabric anisotropy is erased at large shear strains.
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a numerical analysis of the shear behavior of Granular Soil with fines
Particuology, 2015Co-Authors: Beibing Dai, Jun Yang, Xiaodong LuoAbstract:Abstract Shear behavior of Granular Soil with fines is investigated using the discrete element method (DEM) and particle arrangements and inter-particle contacts during shear are examined. The DEM simulation reveals that fine particles play a vital role in the overall response of Granular Soil to shearing. The occurrence of liquefaction and temporary reduction of strength is ascribed mainly to the loss of support from the fine particle contacts (S–S) and fine particle-to-large particle contacts (S–L) as a consequence of the removal of fine particles from the load-carrying skeleton. The dilative strain-hardening response following the strain-softening response is associated with the migration of fine particles back into the load-carrying skeleton, which is thought to enhance the stiffness of the Soil skeleton. During shear, the unit normal vector of the large particle-to-large particle (L–L) contact has the strongest fabric anisotropy, and the S–S contact unit normal vector possesses the weakest anisotropy, suggesting that the large particles play a dominant role in carrying the shear load. It is also found that, during shear, fine particles are prone to rolling at contacts while the large particles are prone to sliding, mainly at the S–L and L–L contacts.
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A numerical analysis of the shear behavior of Granular Soil with fines
Particuology, 2015Co-Authors: Beibing Dai, Jun Yang, Xiaodong LuoAbstract:Shear behavior of Granular Soil with fines is investigated using the discrete element method (DEM) and particle arrangements and inter-particle contacts during shear are examined. The DEM simulation reveals that fine particles play a vital role in the overall response of Granular Soil to shearing. The occurrence of liquefaction and temporary reduction of strength is ascribed mainly to the loss of support from the fine particle contacts (S-S) and fine particle-to-large particle contacts (S-L) as a consequence of the removal of fine particles from the load-carrying skeleton. The dilative strain-hardening response following the strain-softening response is associated with the migration of fine particles back into the load-carrying skeleton, which is thought to enhance the stiffness of the Soil skeleton. During shear, the unit normal vector of the large particle-to-large particle (L-L) contact has the strongest fabric anisotropy, and the S-S contact unit normal vector possesses the weakest anisotropy, suggesting that the large particles play a dominant role in carrying the shear load. It is also found that, during shear, fine particles are prone to rolling at contacts while the large particles are prone to sliding, mainly at the S-L and L-L contacts. © 2015 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy ofSciences. Published by Elsevier B.V. All rights reserved
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undrained anisotropy and rotational shear in Granular Soil
Geotechnique, 2007Co-Authors: Z X Yang, Jun YangAbstract:The impact of fabric anisotropy on the behaviour of Granular Soil remains a subject of great interest. In particular, the effects of principal stress rotation on the undrained response of saturated sand are not fully understood. This paper describes an experimental investigation conducted in an automated hollow cylinder apparatus into the undrained anisotropic behaviour of saturated sand in rotational shear, which is defined as a class of non-proportional loading with a continuous rotation of the principal stress directions but a constant deviatoric stress. Special attention in this investigation was placed on the influence of the relative magnitude of the intermediate principal stress, characterised by the parameter b = (σ2 − σ3)/(σ1 − σ3), on the pore pressure response and deformation characteristics. The experimental observations indicate that Soil specimens, even in very dense state, were weakened by the build-up of pore water pressure in rotational shear. The intermediate principal stress parameter b...
