13 results on '"Bathurst, Richard J"'
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2. Numerical modelling of two full-scale reinforced soil wrapped-face walls.
- Author
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Yu, Yan, Bathurst, Richard J., and Allen, Tony M.
- Subjects
- *
WALLS , *REINFORCED soils , *STIFFNESS (Engineering) , *STRAINS & stresses (Mechanics) , *GEOSYNTHETICS , *MATHEMATICAL models - Abstract
The paper reports the details of numerical models used to predict the performance of two 3.6 m-high well-instrumented wrapped-face walls. The walls were nominally identical except that the reinforcement material in one wall was a steel welded wire mesh and in the other a biaxial polypropylene geogrid. The backfill soil was modelled using both linear and nonlinear elastic-plastic constitutive models. A general hyperbolic (nonlinear) axial load-strain-time model was used for the reinforcement. The numerical results show good agreement with measured performance features for the welded wire mesh wrapped-face wall. Agreement between numerical predictions of facing displacements and maximum reinforcement loads was less accurate for the very flexible geogrid wrapped-face wall. The discrepancies are believed to be related to the unusually flexible wrapped face used in the geogrid wall construction. Numerically predicted and measured maximum reinforcement loads are compared to loads using the AASHTO reinforcement strength-based design approach (Simplified Method) and the Simplified Stiffness Method which is an empirical reinforcement stiffness-based method. The paper provides physical test data that can be used to benchmark other numerical models, highlights lessons learned during the development of the models, and identifies reasonable expectations for numerical model accuracy for models of similar complexity used to simulate the performance of mechanically stabilized earth (MSE) wall structures under operational conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
3. Modified unit cell approach for modelling geosynthetic-reinforced column-supported embankments.
- Author
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Yu, Yan, Bathurst, Richard J., and Damians, Ivan P.
- Subjects
- *
GEOSYNTHETICS , *EMBANKMENTS , *COLUMNS , *UNIT cell , *STRAINS & stresses (Mechanics) - Abstract
Geosynthetic-reinforced and column-supported (GRCS) embankments have proven to be an effective construction technique for fills on soft foundations. The paper introduces a modified unit cell approach to model GRCS embankments supported by deep mixed column walls. The modified unit cells include linear elastic springs at one or both vertical boundaries to simulate lateral displacements of the embankment fill and foundation soil. The finite difference program FLAC is used to compare numerical outcomes using the modified unit cells with those using the typical unit cell arrangement with lateral rigid side boundaries. Numerical results demonstrate good agreement between simulations using small-strain and large-strain modes in some cases and large differences in other cases. Lateral displacements of the embankment fill and foundation soil using the modified unit cells are shown to have large influence on reinforcement loads. Finally the paper demonstrates that calculated reinforcement loads are sensitive to choice of small-strain or large-strain mode when using program FLAC. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
4. A new approach to evaluate soil-geosynthetic interaction using a novel pullout test apparatus and transparent granular soil.
- Author
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Ezzein, Fawzy M. and Bathurst, Richard J.
- Subjects
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GEOSYNTHETICS , *SOIL granularity , *PARTICLES , *DIGITAL image correlation , *STRAINS & stresses (Mechanics) - Abstract
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. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
5. Influence of toe restraint on reinforced soil segmental walls.
- Author
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Huang, Bingquan, Bathurst, Richard J., Hatami, Kianoosh, and Allen, Tony M.
- Subjects
REINFORCED soils ,STRAINS & stresses (Mechanics) ,SHEAR (Mechanics) ,CRUSHED stone ,COMPUTER simulation ,STIFFNESS (Mechanics) - Abstract
Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2010
- Full Text
- View/download PDF
6. Numerical Study of Reinforced Soil Segmental Walls Using Three Different Constitutive Soil Models.
- Author
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Bingquan Huang, Bathurst, Richard J., and Hatami, Kianoosh
- Subjects
- *
REINFORCED soils , *SOILS , *POLYMERIC composites , *GEOGRIDS , *STRAINS & stresses (Mechanics) - Abstract
A numerical finite-difference method (FLAC) model was used to investigate the influence of constitutive soil model on predicted response of two full-scale reinforced soil walls during construction and surcharge loading. One wall was reinforced with a relatively extensible polymeric geogrid and the other with a relatively stiff welded wire mesh. The backfill sand was modeled using three different constitutive soil models varying as follows with respect to increasing complexity: linear elastic-plastic Mohr-Coulomb, modified Duncan-Chang hyperbolic model, and Lade’s single hardening model. Calculated results were compared against toe footing loads, foundation pressures, facing displacements, connection loads, and reinforcement strains. In general, predictions were within measurement accuracy for the end-of-construction and surcharge load levels corresponding to working stress conditions. However, the modified Duncan-Chang model which explicitly considers plane strain boundary conditions is a good compromise between prediction accuracy and availability of parameters from conventional triaxial compression testing. The results of this investigation give confidence that numerical FLAC models using this simple soil constitutive model are adequate to predict the performance of reinforced soil walls under typical operational conditions provided that the soil reinforcement, interfaces, boundaries, construction sequence, and soil compaction are modeled correctly. Further improvement of predictions using more sophisticated soil models is not guaranteed. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
7. Influence of constitutive model on numerical simulation of EPS seismic buffer shaking table tests
- Author
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Zarnani, Saman and Bathurst, Richard J.
- Subjects
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POLYSTYRENE , *ENGINEERING models , *SEISMIC testing , *DAMPING (Mechanics) , *DYNAMIC testing of materials , *COMPUTER simulation , *STRAINS & stresses (Mechanics) , *NUMERICAL analysis - Abstract
Abstract: The paper describes two constitutive models for the simulation of expanded polystyrene (EPS) seismic buffer shaking table tests previously reported by the writers. The first model is linear elastic–plastic with Mohr–Coulomb criterion and Rayleigh damping. The second is called the equivalent-linear method (ELM) which incorporates hysteretic load–unload cycles using Masing-type functions and strain-dependent shear modulus and damping ratio functions. The constitutive models were applied to both the geofoam buffer and sand backfill in both approaches. Both models are shown to capture qualitative features of measured peak load-time response of the physical tests. The advanced ELM model gave predictions that were closer to the measured results for the seismic buffer test with the most compressible EPS when model accelerations and total wall forces were greatest. However, the simpler model is judged to be sufficiently accurate for practical purposes when the dynamic force increment is considered only. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
8. Predicted Loads in Steel Reinforced Soil Walls Using the AASHTO Simplified Method.
- Author
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Bathurst, Richard J., Nernheim, Axel, and Allen, Tony M.
- Subjects
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TECHNICAL specifications , *STRAINS & stresses (Mechanics) , *MECHANICAL loads , *DYNAMIC testing of materials , *SOIL stabilization , *PHYSICAL measurements , *PENETRATION resistance of concrete , *REQUIREMENTS engineering - Abstract
The paper investigates the accuracy of the AASHTO simplified method by using load measurements reported in a large database of full-scale instrumented walls for bar mat, welded wire, and steel strip soil reinforced walls. The accuracy of the AASHTO simplified method is quantified by computing the mean and coefficient of variation of the ratio (bias) of measured loads under operational conditions to predicted loads. The paper shows that for steel strip walls, the AASHTO simplified method is reasonably accurate for granular backfill soils with friction angles less than 45°. For bar mat walls, the method is demonstrated to be slightly conservative. The simplified method underpredicts reinforcement loads at shallow overburden depths for steel strip walls with backfill friction angles greater than 45° due to compaction-related effects. It is concluded that these compaction-induced loads near the wall top do not contribute to internal instability due to pullout. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
9. Development of the K- stiffness method for geosynthetic reinforced soil walls constructed with c-φ soils.
- Author
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Miyata, Yoshihisa and Bathurst, Richard J.
- Subjects
GEOSYNTHETICS ,MATERIAL plasticity ,COHESION ,RETAINING walls ,EARTH pressure ,STRAINS & stresses (Mechanics) ,COMPOSITE materials ,CONSTRUCTION materials - Abstract
Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2007
- Full Text
- View/download PDF
10. Reply to the discussions on “The influence of facing stiffness on the performance of two geosynthetic reinforced soil retaining walls”.
- Author
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Bathurst, Richard J., Vlachopoulos, Nicholas P., Walters, Dave L., Burgess, Peter G., and Allen, Tony M.
- Subjects
RETAINING walls ,EARTH pressure ,STRAINS & stresses (Mechanics) ,WALL design & construction ,REINFORCED concrete ,COMPOSITE materials ,CONSTRUCTION materials ,ENGINEERING geology - Abstract
The article presents a response to the discussions made by Robert K. Barrett and Dov Leshchinsky on the authors' paper "The influence of facing stiffness on the performance of two geosynthetic reinforced soil retaining walls." They appreciate the comments raised by Barrett and Leshchinsky. In doing so, they clarify and elucidate a number of points related to the details and contingents of the test program described in the referring paper. Moreover, they provide various implications to current practice.
- Published
- 2007
- Full Text
- View/download PDF
11. New Method for Prediction of Loads in Steel Reinforced Soil Walls.
- Author
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Allen, T. M., Bathurst, Richard J., Holtz, Robert D., Lee, Wei F., and Walters, D.
- Subjects
- *
STRAINS & stresses (Mechanics) , *WALLS , *STEEL , *GEOSYNTHETICS , *SOIL structure , *SOILS - Abstract
The paper describes a new working stress design methodology introduced by the writers for geosynthetic reinforced soil walls (K-Stiffness Method) that is now extended to steel reinforced soil walls. A large database of full-scale steel reinforced soil walls (a total of 20 fully instrumented wall sections) was used to develop the new design methodology. The effects of global wall stiffness, soil strength, reinforcement layer spacing, and wall height were investigated. Results of simple statistical analyses using the ratio of measured to predicted peak reinforcement loads (i.e., method bias) demonstrate the improved prediction accuracy. The AASHTO Simplified Method results in an average method bias of 1.1 with a coefficient of variation (COV) of 45%, whereas the proposed K-Stiffness Method results in an average bias of 0.95 and a COV of 32%. Soil strength was found to have limited influence on reinforcement loads for steel reinforced soil walls, especially for high shear strength soils, while global wall stiffness and wall height had a major influence on reinforcement loads. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
12. A new working stress method for prediction of reinforcement loads in geosynthetic walls.
- Author
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Allen, T M, Bathurst, Richard J, Holtz, Robert D, Walters, D, and Lee, Wei F
- Subjects
STRAINS & stresses (Mechanics) ,ELASTIC solids ,FLEXURE ,MECHANICS (Physics) ,GEOSYNTHETICS ,WALLS - Abstract
Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2003
- Full Text
- View/download PDF
13. Influence of choice of FLAC and PLAXIS interface models on reinforced soil–structure interactions.
- Author
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Yu, Yan, Damians, Ivan P., and Bathurst, Richard J.
- Subjects
- *
FINITE difference method , *REINFORCED concrete , *SOIL structure , *NUMERICAL analysis , *STRAINS & stresses (Mechanics) - Abstract
The choice of structure element to simulate soil reinforcement and soil–structure interaction details for numerical modelling of mechanically stabilized earth (MSE) walls can have a significant influence on numerical outcomes. Program FLAC (finite difference method) offers three different options (beam, cable and strip element) to model the reinforcement and program PLAXIS (finite element method) has two (beam and geogrid element). Both programs use different models and properties to simulate the mechanical behaviour of the interface between dissimilar materials. The paper describes the details of the linear elastic Mohr–Coulomb interface model available in the two software packages to model material interaction and how to select model parameters to give the same numerical outcomes. The numerical results quantitatively demonstrate the conditions that give good agreement between the two programs for the same steel strip reinforced soil–structure problem and the situations where they do not. For example, the paper demonstrates that results can be very different depending on the type of structure element used to model horizontal reinforcement layers that are discontinuous in the plane-strain direction. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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