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Fumio Tatsuoka - One of the best experts on this subject based on the ideXlab platform.
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residual deformation of geosynthetic reinforced sand in Plane Strain Compression affected by viscous properties of geosynthetic reinforcement
Soils and Foundations, 2008Co-Authors: Warat Kongkitkul, Daiki Hirakawa, Fumio TatsuokaAbstract:A series of Plane Strain Compression (PSC) tests were performed on large sand specimens unreinforced or reinforced with prototype geosynthetic reinforcements, either of two geogrid types and one geocomposite type. Local tensile Strains in the reinforcement were measured by using two types of Strain gauges. Sustained loading (SL) under fixed boundary stress conditions and cyclic loading (CL) tests were performed during otherwise monotonic loading at a constant Strain rate to evaluate the development of creep deformation by SL and residual deformation by CL of geosynthetic-reinforced sand and also residual Strains in the reinforcement by these loading histories. It is shown that the creep deformation of geosynthetic-reinforced sand develops due to the viscous properties of both sand and geosynthetic reinforcement, while the residual deformation of geosynthetic-reinforced sand during CL (defined at the peak stress state during CL) consists of two components: i) the one by the viscous properties of sand and reinforcement; and ii) the other by rate-independent cyclic loading effects with sand. The development of residual deformation of geosynthetic-reinforced sand by SL and CL histories had no negative effects on the subsequent stress-Strain behaviour and the compressive strength was maintained as the original value or even became larger by such SL and CL histories. The local tensile Strains in the geosynthetic reinforcement arranged in the sand specimen subjected to SL decreased noticeably with time, due mainly to lateral compressive creep Strains in sand during SL of geosynthetic-reinforced sand. This result indicates that, with geosynthetic-reinforced soil structures designed to have a sufficiently high safety factor under static loading conditions because of seismic design, it is overly conservative to assume that the tensile load in the geosynthetic reinforcement is maintained constant for long life time. Moreover, during CL of geosynthetic-reinforced sand, the residual tensile Strains in the geosynthetic reinforcement did not increase like global Strains in the geosynthetic-reinforced sand that increased significantly during CL. These different trends of behaviour were also due to the creep compressive Strains in the lateral direction of sand that developed during CL of geosynthetic-reinforced sand.
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effects of geosynthetic reinforcement type on the strength and stiffness of reinforced sand in Plane Strain Compression
Soils and Foundations, 2007Co-Authors: Warat Kongkitkul, Daiki Hirakawa, Fumio Tatsuoka, Taro KanemaruAbstract:The effects of geosynthetic reinforcement type on the strength and stiffness of reinforced sand were evaluated by performing a series of drained Plane Strain Compression tests on large sand specimens. The reinforcement type is described in terms of the degree of unification of the constituting components (for geocomposites) as well as the tensile strength and stiffness, the covering ratio and others (for geocomposites and geogrids). Sand specimens reinforced with different geosynthetic reinforcement types exhibited significantly different reinforcing effects. A geocomposite made of a woven geotextile sheet sandwiched firmly with two sheets of non-woven geotextile, having a 100% effective covering ratio, exhibited reinforcing effects higher than typical stiff and strong geogrids. With some geocomposite types, the reinforcing effects increase substantially by better unifying longitudinally arranged stiff and strong yarns and non-woven geotextile sheets. When fixed firm to the yarns, the non-woven geotextile sheets function like the transversal members of a geogrid by locally transmitting load activated by interaction with the backfill to the yarns. These geocomposites can exhibit reinforcing effects equivalent to those with stiff and strong geogrids. Local Strain fields of the specimens are presented to show that, for reinforced sand, the peak stress state reached is always associated with the development of shear band(s) in the sand and a higher peak strength is achieved when the Strain localisation starts at a larger global axial Strain due to better reinforcing effects.
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rate dependent load Strain behaviour of geogrid arranged in sand under Plane Strain Compression
Soils and Foundations, 2007Co-Authors: Warat Kongkitkul, Fumio Tatsuoka, Daiki HirakawaAbstract:A number of previous experimental studies showed that polymer geogrid reinforcement as well as sand exhibit significantly rate-dependent behaviour. The viscous properties of polymer geogrids and Toyoura sand were independently evaluated by changing stepwise the Strain rate as well as performing sustained loading and load/stress relaxation tests during otherwise monotonic loading in, respectively, tensile loading tests and drained Plane Strain Compression (PSC) tests. The viscous properties of the two types of material were separately formulated in the same framework of non-linear three-component rheology model. The viscous response of geogrid-reinforced sand in PSC is significant, controlled by viscous properties of geogrid and sand. Local Strain distributions in the reinforced sand specimen were evaluated by photogrametric analysis and used to determine the time history of the tensile Strain in the geogrid. The time history of tensile load activated in the geogrid during sustained loading of reinforced sand specimen was deduced by analysing the measured time history of geogrid Strain by the non-linear three-component model. It was found that the tensile load in the geogrid reinforcement arranged in a sand specimen subjected to fixed boundary loads could decrease with time. In that case, the possibility of creep rupture of geogrid is very low.
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FEM SIMULATION OF THE VISCOUS EFFECTS ON THE STRESS-Strain BEHAVIOUR OF SAND IN Plane Strain Compression
Soils and Foundations, 2006Co-Authors: Mohammed Saiful Alam Siddiquee, Fumio Tatsuoka, Tadatsugu TanakaAbstract:A stress-Strain model called TESRA (Temporary Effects of Strain Rate and Acceleration), described in a non-linear three-component framework, has been proposed to simulate the effects of viscous property on the stress-Strain behaviour observed in drained Plane Strain Compression (PSC) tests on clean sands. According to the TESRA model, the current viscous stress component is obtained by integrating for a given history of irreversible Strain increments of viscous stress component that developed by respective instantaneous irrecoverable Strain increment and its rate and have decayed with an increase in the irreversible Strain until the present. The TESRA model was implemented into a generalized elasto-plastic isotropic Strain-hardening non-linear FE code. The integration scheme to obtain the viscous and inviscid stress components according to the TESRA model in FEM analysis needs some specific considerations including the relevant choice of the suitable rate parameter. The shear stress—shear (or axial) Strain—time relations from five drained PSC tests on saturated Toyoura sand and air-dried Hostun sand were successfully simulated by the FE code embedded with the TESRA model. It is shown that the FE code can simulate the time-dependent stress-Strain behaviour of sand accurately without spending any significant extra computational time or storage. The results of simulation using one element and multi-element are essentially the same.
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Plane Strain Compression behaviour of geogrid reinforced sand and its numerical analysis
Soils and Foundations, 2000Co-Authors: Fangle Peng, Fumio Tatsuoka, Daiki Hirakawa, Nozomu Kotake, Tadatsugu TanakaAbstract:Plane Strain Compression tests were performed on large specimens that were either unreinforced or reinforced with 6 or 11 layers of geogrid, both 57.0 cm in height and 24.4 cm×21.4 cm in cross-section. It is shown that the effects of covering ratio for each grid layer is much more important than the total tensile stiffness of grid within the limits of the test conditions in this study. Numerical analysis of the test results by a Plane Strain non-linear elasto-plastic FEM was performed considering Strain localisation as well as anisotropic stress-Strain behaviour of sand and interface properties. The geogrid was modelled as a planar reinforcement. Not only the pre-peak stress-Strain behaviour of the unreinforced and reinforced specimens, but also the peak strength, post-peak behaviour and dilatancy characteristics from the FEM analysis all compared well with those from the physical tests. The effects of reinforcement rigidity and covering ratio were also well simulated. The relationship between the reinforcement covering ratio in the physical tests and the equivalent interface friction angle for the FEM analysis that provides the same reinforcing effects is presented. The mechanism of tensile-reinforcing is analysed based on local stress paths within the reinforced sand obtained from the FEM analysis.
Tadatsugu Tanaka - One of the best experts on this subject based on the ideXlab platform.
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FEM SIMULATION OF THE VISCOUS EFFECTS ON THE STRESS-Strain BEHAVIOUR OF SAND IN Plane Strain Compression
Soils and Foundations, 2006Co-Authors: Mohammed Saiful Alam Siddiquee, Fumio Tatsuoka, Tadatsugu TanakaAbstract:A stress-Strain model called TESRA (Temporary Effects of Strain Rate and Acceleration), described in a non-linear three-component framework, has been proposed to simulate the effects of viscous property on the stress-Strain behaviour observed in drained Plane Strain Compression (PSC) tests on clean sands. According to the TESRA model, the current viscous stress component is obtained by integrating for a given history of irreversible Strain increments of viscous stress component that developed by respective instantaneous irrecoverable Strain increment and its rate and have decayed with an increase in the irreversible Strain until the present. The TESRA model was implemented into a generalized elasto-plastic isotropic Strain-hardening non-linear FE code. The integration scheme to obtain the viscous and inviscid stress components according to the TESRA model in FEM analysis needs some specific considerations including the relevant choice of the suitable rate parameter. The shear stress—shear (or axial) Strain—time relations from five drained PSC tests on saturated Toyoura sand and air-dried Hostun sand were successfully simulated by the FE code embedded with the TESRA model. It is shown that the FE code can simulate the time-dependent stress-Strain behaviour of sand accurately without spending any significant extra computational time or storage. The results of simulation using one element and multi-element are essentially the same.
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Plane Strain Compression behaviour of geogrid reinforced sand and its numerical analysis
Soils and Foundations, 2000Co-Authors: Fangle Peng, Fumio Tatsuoka, Daiki Hirakawa, Nozomu Kotake, Tadatsugu TanakaAbstract:Plane Strain Compression tests were performed on large specimens that were either unreinforced or reinforced with 6 or 11 layers of geogrid, both 57.0 cm in height and 24.4 cm×21.4 cm in cross-section. It is shown that the effects of covering ratio for each grid layer is much more important than the total tensile stiffness of grid within the limits of the test conditions in this study. Numerical analysis of the test results by a Plane Strain non-linear elasto-plastic FEM was performed considering Strain localisation as well as anisotropic stress-Strain behaviour of sand and interface properties. The geogrid was modelled as a planar reinforcement. Not only the pre-peak stress-Strain behaviour of the unreinforced and reinforced specimens, but also the peak strength, post-peak behaviour and dilatancy characteristics from the FEM analysis all compared well with those from the physical tests. The effects of reinforcement rigidity and covering ratio were also well simulated. The relationship between the reinforcement covering ratio in the physical tests and the equivalent interface friction angle for the FEM analysis that provides the same reinforcing effects is presented. The mechanism of tensile-reinforcing is analysed based on local stress paths within the reinforced sand obtained from the FEM analysis.
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an insight into the failure of reinforced sand in Plane Strain Compression by fem simulation
Soils and Foundations, 1999Co-Authors: Nozomu Kotake, Tadatsugu Tanaka, Mohammed Saiful Alam Siddiquee, Fumio Tatsuoka, Hiromoto YamauchiAbstract:An FEM simulation of Plane Strain Compression tests of dense Toyoura sand reinforced with reinforcement having a wide range of stiffness is described. Strain localisation is taken into account by modelling a shear band having a specific thickness and specific Strain-softening properties determined based on experimental results. Global and local behaviour of the unreinforced and reinforced sand observed in Plane Strain Compression tests are properly simulated.
C M Sellars - One of the best experts on this subject based on the ideXlab platform.
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identification of rheological parameters on the basis of Plane Strain Compression tests on specimens of various initial dimensions
Computational Materials Science, 2006Co-Authors: B Kowalski, C M Sellars, Maciej PietrzykAbstract:Abstract The work is based on the assumption that the flow stress of a material should be insensitive to the method of plastometric testing or to the size of the samples. It is generally observed, however, that various methods of testing yield different values of the flow stress. Endeavours are made to eliminate these differences and various methods of correction of the results of the tests have been developed. The particular objective of the present work is to check the capabilities of the inverse technique to obtain consistent flow stress data when this technique is applied to Plane Strain Compression tests performed on one material with various dimensions of the specimens. The experiments included Plane Strain Compression for specimens measuring 2.5, 5 and 10 mm initial thickness. The inverse algorithm developed by the authors was used in the investigation. Application of the inverse analysis to the interpretation of the results of these tests allowed the conclusion that the results obtained for various specimen geometries coincide very closely. This analysis has been further used for evaluation of various conventional methods for correction to account for the influence of inhomogeneity of Strain and temperature.
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measurement of flow stress in hot Plane Strain Compression tests
Materials at High Temperatures, 2006Co-Authors: Malcolm S Loveday, C M Sellars, A J Lacey, G J Mahon, B Roebuck, E J Palmiere, M R Van Der WindenAbstract:AbstractThis Good Practice Guide is applicable to hot (isothermal) Plane Strain Compression (PSC) tests at medium to high rates of Strain (10–3 to 102 s–1) at deformation temperatures below the solidus.Guidance is provided on appropriate testpiece geometries and methods of verifying the temperature distribution along the length of the testpiece. Flow diagrams are given showing all the steps that are necessary, including the correction factors that need to be applied for breadth spreading of the testpiece; machine origin and compliance, friction effects and deformational heating. Details are given of the calibration procedures that should be followed to provide traceability to the National Measurement System.The development of the procedure has been supported through experimental tests on type 316 austenitic stainless steel at 1050–1150°C and an aluminium alloy, AA5052, at 300°C to 500°C at Strain rates ranging up to 100 s–1.Technical input to the document has been provided by a steering group comprising a...
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correction of Plane Strain Compression data for the effects of inhomogeneous deformation
Materials Science and Technology, 2003Co-Authors: B Kowalski, A J Lacey, C M SellarsAbstract:Plane Strain Compression tests to investigate the effects of heterogeneity of deformation on various initial specimen geometries have been carried out. Equations for correction of nominal Strain and Strain rate to slip line field Strain and Strain rate have been developed and applied to experimental flow stress-Strain data. Investigation of the deformed specimens showed evidence of changing friction conditions during deformation, therefore a simple function allowing friction to change was applied. The corrections eliminate the geometry effect observed in the initial data and lead to modified constitutive equations for flow stress.
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measuring flow stress in hot Plane Strain Compression tests
2002Co-Authors: A J Lacey, C M Sellars, Malcolm S Loveday, G J Mahon, B Roebuck, M R Van Der WindenAbstract:This document has been produced to complement the Measurement Good Practice Guide No 3 which describes current best UK practice for measuring hot flow stress in metallic materials using Hot Axisymmetric Compression (HAC). This Guide is applicable to hot (isothermal) Plane Strain Compression (PSC) tests at medium to high rates of Strain at deformation temperatures below the solidus. Technical input to the document has been provided by a steering group comprising academic researchers, representatives of industrial users and producers of a wide range of engineering materials. An experimental programme was conducted during the preparation of this document to underpin the procedures in this guide.
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modelling the hot Plane Strain Compression test part 1 effect of specimen geometry Strain rate and friction on deformation
Materials Science and Technology, 2001Co-Authors: M S Mirza, C M SellarsAbstract:AbstractThermomechanically coupled finite element analysis of the hot Plane Strain Compression test has been carried out to investigate the effect of various test parameters on the measured response and deformation of specimens. The results are presented in a series of papers. In this paper (Part 1), the results of two-dimensional simulations are discussed, evaluating the effects of material type, specimen geometry, Strain rate, and friction on the overall deformation behaviour. The effects of spread and friction are detailed in Part 2, and the effects of asymmetry during the test are detailed in Part 3. The present results show that the local deformation behaviour is independent of the type of material and Strain rate, at least up to 50 s-1. The behaviour, however, depends strongly on friction and initial specimen geometry, with deformation becoming more uniform with decreasing initial specimen thickness, i.e. with increasing tool width w to specimen thickness h ratio. The deformation is conStrained with...
Bin Tang - One of the best experts on this subject based on the ideXlab platform.
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serrated flow behavior and microstructure evolution of inconel 625 superalloy during Plane Strain Compression with different Strain rates
Journal of Alloys and Compounds, 2021Co-Authors: Xudong Liu, Bin Tang, Jiangkun Fan, Yuelin Song, Degui Liu, Ruihao Yuan, Jun Wang, Hongchao KouAbstract:Abstract Strain rate played an important role in the forming process of metal and alloy. In the present work, the effect of Strain rate on deformation behavior and microstructure evolution of thermal-rolled Inconel 625 superalloy were systematically investigated by Plane-Strain Compression (PSC) test at 1000 °C, and the Strain rate range changed from 1 × 10−3 s−1 to 5 s−1. Obvious serrations occurred in Strain rate range of 5 s−1 - 0.05 s−1 and transformed from type A to type A+B, and type B with decreasing of Strain rate. Microscopic observations from transmission electron microscopy (TEM) indicated that type A and type B serration were related to slip bands nucleation-propagation, and carbon atoms-dislocations interaction, respectively. Electron backscatter diffraction (EBSD) technique and TEM were used to study the dynamic recrystallization (DRX) behavior during PSC. As the Strain rates were greater than 5 s−1, DRX process was accelerated because of high deformed stored energy and adiabatic heating. This is undoubtedly a meaningful find to refine grain size and improve thermal processing efficiency. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) have been confirmed to occur simultaneously during the deformation process, but CDRX played a minor role in DRX nucleation. Texture evolution characteristics were also related to Strain rate. Nearly random texture distribution was obtained as the Strain rate above 0.5 s−1. Obvious Cu, E, S and Cube textures appeared in the Strain rate range of 0.1 s−1–10−2 s−1. Grain orientations showed random distribution at the Strain rate of 10−3 s−1. Moreover, direction should be considered as preferred crystallographic orientations to recrystallization nucleation.
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dynamic recrystallization and texture evolution of ti 22al 25nb alloy during Plane Strain Compression
Journal of Alloys and Compounds, 2018Co-Authors: Hongchao Kou, Bin TangAbstract:Abstract To investigate the dynamic recrystallization (DRX) mechanism and texture evolution of Ti-22Al-25Nb alloy during the thermal mechanical processing, Plane-Strain Compression tests were carried out on Gleeble-3500 thermo-mechanical simulator with various Strains of 0.36, 0.70 and 1.20, respectively. The results show that the microstructures are significantly sensitive to Strains. With the increasing Strain, the increased deformation storage energy provides larger driving force for the movement of dislocation and the migration of boundaries, leading to a distinct increase of DRX degree. The nucleation and growth of DRX grains will cause the rearrangement and annihilation of mobile dislocation, as well as the increase of fLAGBs. Particularly, the evolution of dislocation substructures can be identified as: high density dislocation→subgrain→DRX grain. DRX is the dominant softening mechanism for this studied alloy, including the continuous dynamic recrystallization (CDRX) characterized by the transformation of the low angle grain boundaries (LAGBs) to the high angle grain boundaries (HAGBs), and the discontinuous dynamic recrystallization (DDRX) characterized by the grain boundary bulging. Meanwhile, the DRX behavior exhibits an obvious weakening effect on the deformation textures due to the random orientations of DRX grains.
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deformation behavior of hot rolled in718 superalloy under Plane Strain Compression at elevated temperature
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Liang Cheng, Bin Tang, Jizhen Li, Jinshan LiAbstract:Abstract The hot deformation behavior of hot-rolled IN718 superalloy was studied by Plane Strain Compression in the temperature range of 900–1050 °C and Strain rate range of 10 −3 –10 s −1 . The results showed that the flow curves exhibit weak softening at most deformation conditions. However, intense softening caused by adiabatic heating was observed in the flow curves when the alloy was deformed at high Strain rate (10 s −1 ), and these curves are characterized by unique “double-peak” which cannot be observed in those under uniaxial Compression. Intensive Strain localization and dynamic recrystallization occurred in the deformed specimens. Constitutive model based on the hyperbolic-sine equation was established to characterize the dependence of flow stress on Strain, Strain rate and temperature, and the activation energy was estimated to be 429 kJ/mol. The processing maps were constructed to evaluate the power dissipation efficiency ( η ) and recognize the instability regimes. Optimum parameters were obtained in the temperature range of 1030–1050 °C at Strain rates of 0.02–0.1 s −1 for Plane Strain Compression.
Daiki Hirakawa - One of the best experts on this subject based on the ideXlab platform.
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residual deformation of geosynthetic reinforced sand in Plane Strain Compression affected by viscous properties of geosynthetic reinforcement
Soils and Foundations, 2008Co-Authors: Warat Kongkitkul, Daiki Hirakawa, Fumio TatsuokaAbstract:A series of Plane Strain Compression (PSC) tests were performed on large sand specimens unreinforced or reinforced with prototype geosynthetic reinforcements, either of two geogrid types and one geocomposite type. Local tensile Strains in the reinforcement were measured by using two types of Strain gauges. Sustained loading (SL) under fixed boundary stress conditions and cyclic loading (CL) tests were performed during otherwise monotonic loading at a constant Strain rate to evaluate the development of creep deformation by SL and residual deformation by CL of geosynthetic-reinforced sand and also residual Strains in the reinforcement by these loading histories. It is shown that the creep deformation of geosynthetic-reinforced sand develops due to the viscous properties of both sand and geosynthetic reinforcement, while the residual deformation of geosynthetic-reinforced sand during CL (defined at the peak stress state during CL) consists of two components: i) the one by the viscous properties of sand and reinforcement; and ii) the other by rate-independent cyclic loading effects with sand. The development of residual deformation of geosynthetic-reinforced sand by SL and CL histories had no negative effects on the subsequent stress-Strain behaviour and the compressive strength was maintained as the original value or even became larger by such SL and CL histories. The local tensile Strains in the geosynthetic reinforcement arranged in the sand specimen subjected to SL decreased noticeably with time, due mainly to lateral compressive creep Strains in sand during SL of geosynthetic-reinforced sand. This result indicates that, with geosynthetic-reinforced soil structures designed to have a sufficiently high safety factor under static loading conditions because of seismic design, it is overly conservative to assume that the tensile load in the geosynthetic reinforcement is maintained constant for long life time. Moreover, during CL of geosynthetic-reinforced sand, the residual tensile Strains in the geosynthetic reinforcement did not increase like global Strains in the geosynthetic-reinforced sand that increased significantly during CL. These different trends of behaviour were also due to the creep compressive Strains in the lateral direction of sand that developed during CL of geosynthetic-reinforced sand.
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effects of geosynthetic reinforcement type on the strength and stiffness of reinforced sand in Plane Strain Compression
Soils and Foundations, 2007Co-Authors: Warat Kongkitkul, Daiki Hirakawa, Fumio Tatsuoka, Taro KanemaruAbstract:The effects of geosynthetic reinforcement type on the strength and stiffness of reinforced sand were evaluated by performing a series of drained Plane Strain Compression tests on large sand specimens. The reinforcement type is described in terms of the degree of unification of the constituting components (for geocomposites) as well as the tensile strength and stiffness, the covering ratio and others (for geocomposites and geogrids). Sand specimens reinforced with different geosynthetic reinforcement types exhibited significantly different reinforcing effects. A geocomposite made of a woven geotextile sheet sandwiched firmly with two sheets of non-woven geotextile, having a 100% effective covering ratio, exhibited reinforcing effects higher than typical stiff and strong geogrids. With some geocomposite types, the reinforcing effects increase substantially by better unifying longitudinally arranged stiff and strong yarns and non-woven geotextile sheets. When fixed firm to the yarns, the non-woven geotextile sheets function like the transversal members of a geogrid by locally transmitting load activated by interaction with the backfill to the yarns. These geocomposites can exhibit reinforcing effects equivalent to those with stiff and strong geogrids. Local Strain fields of the specimens are presented to show that, for reinforced sand, the peak stress state reached is always associated with the development of shear band(s) in the sand and a higher peak strength is achieved when the Strain localisation starts at a larger global axial Strain due to better reinforcing effects.
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rate dependent load Strain behaviour of geogrid arranged in sand under Plane Strain Compression
Soils and Foundations, 2007Co-Authors: Warat Kongkitkul, Fumio Tatsuoka, Daiki HirakawaAbstract:A number of previous experimental studies showed that polymer geogrid reinforcement as well as sand exhibit significantly rate-dependent behaviour. The viscous properties of polymer geogrids and Toyoura sand were independently evaluated by changing stepwise the Strain rate as well as performing sustained loading and load/stress relaxation tests during otherwise monotonic loading in, respectively, tensile loading tests and drained Plane Strain Compression (PSC) tests. The viscous properties of the two types of material were separately formulated in the same framework of non-linear three-component rheology model. The viscous response of geogrid-reinforced sand in PSC is significant, controlled by viscous properties of geogrid and sand. Local Strain distributions in the reinforced sand specimen were evaluated by photogrametric analysis and used to determine the time history of the tensile Strain in the geogrid. The time history of tensile load activated in the geogrid during sustained loading of reinforced sand specimen was deduced by analysing the measured time history of geogrid Strain by the non-linear three-component model. It was found that the tensile load in the geogrid reinforcement arranged in a sand specimen subjected to fixed boundary loads could decrease with time. In that case, the possibility of creep rupture of geogrid is very low.
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Plane Strain Compression behaviour of geogrid reinforced sand and its numerical analysis
Soils and Foundations, 2000Co-Authors: Fangle Peng, Fumio Tatsuoka, Daiki Hirakawa, Nozomu Kotake, Tadatsugu TanakaAbstract:Plane Strain Compression tests were performed on large specimens that were either unreinforced or reinforced with 6 or 11 layers of geogrid, both 57.0 cm in height and 24.4 cm×21.4 cm in cross-section. It is shown that the effects of covering ratio for each grid layer is much more important than the total tensile stiffness of grid within the limits of the test conditions in this study. Numerical analysis of the test results by a Plane Strain non-linear elasto-plastic FEM was performed considering Strain localisation as well as anisotropic stress-Strain behaviour of sand and interface properties. The geogrid was modelled as a planar reinforcement. Not only the pre-peak stress-Strain behaviour of the unreinforced and reinforced specimens, but also the peak strength, post-peak behaviour and dilatancy characteristics from the FEM analysis all compared well with those from the physical tests. The effects of reinforcement rigidity and covering ratio were also well simulated. The relationship between the reinforcement covering ratio in the physical tests and the equivalent interface friction angle for the FEM analysis that provides the same reinforcing effects is presented. The mechanism of tensile-reinforcing is analysed based on local stress paths within the reinforced sand obtained from the FEM analysis.