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A Geosynthetic Modular Block Connection Creep Test Apparatus, Methodology, and Interpretation
A test protocol for the quantification of creep between modular block (segmental) facing units and geosynthetic reinforcement can be found in a Federal Highway Administration guidance document first published in 2001. However, to date the utility of the proposed method has not been examined in a systematic manner nor have test results been reported in the research literature. The paper describes a test apparatus and reports the results of a series of connection creep tests that demonstrate details of the proposed methodology and lessons learned. Important recommendations for data interpretation are presented for the first time. An additional practical result of this study is a consistent method to calculate the connection creep reduction factor required for design using the results of conventional short-term connection test results and connection creep-rupture curves.
ID: 3899
Publication: Geotechnical Testing Journal - March 2010
Vol: 33
Issue: 2
Publisher: ASTM International
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Author: Richard J. Bathurst and Bingquan Huang
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Implementation of a Critical State Two-Surface Model to Evaluate the Response of Geosynthetic Reinforced Pavements
A finite element model was developed using ABAQUS software package to investigate the effect of placing geosynthetic reinforcement within the base course layer on the response of a flexible pavement structure. A critical state two-surface constitutive model was first modified to represent the behavior of base course materials under the unsaturated field conditions. The modified model was then implemented into ABAQUS through a user defined subroutine, UMAT. The implemented model was validated using the results of laboratory triaxial tests. Finite element analyses were then conducted on different unreinforced and geosynthetic reinforced flexible pavement sections. The results of this study demonstrated the ability of the modified critical state two-surface constitutive model to predict, with good accuracy, the response of the considered base course material at its optimum field conditions when subjected to cyclic as well as static loads. The results of the finite element analyses showed that the geosynthetic reinforcement reduced the lateral strains within the base course and subgrade layers. Furthermore, the inclusion of the geosynthetic layer resulted in a significant reduction in the vertical and shear strains at the top of the subgrade layer. The improvement of the geosynthetic layer was found to be more pronounced in the development of the plastic strains rather than the resilient strains. The reinforcement benefits were enhanced as its elastic modulus increased.
ID: 3898
Publication: International Journal of Geomechanics - 2010
Publisher: ASCE
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Author: Munir D. Nazzal, Murad Y. Abu-Farsakh, and Louay N. Mohammad
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New procedure for measuring adherence between a geosynthetic material and a bituminous mixture
The aim of this investigation was to analyze the adherence between two layers of bituminous mixture when a geosynthetic material is placed between them. A new monotonic test procedure was developed that enables the evaluation of the influence of the binder type and content, and the typology of the geosynthetic material used. The validity of the procedure was demonstrated using dynamic tests. The results confirmed that highest adherence between layers is obtained through geogrids, with optimal residual binder content of 0.30 kg/m2. In contrast, the tests with geotextiles were found to be less sensitive to binder content, with lower shear resistance for higher contents of binder.
ID: 3894
Publication: Geotextiles and Geomembranes - In Press, 2010
Publisher: Elsevier
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Author: D. Zamora-Barraza, M. Calzada-Peréz, D. Castro-Fresno, and A. Vega-Zamanillo
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Textile Minister Launches Project for Increased Use of Jute Geotextiles
From the India-based Business Coordination House (BCH) January-March 2010 Newsletter: "The mantra for survival of jute industry is product diversification and the Jute Geotextiles (JGT) provide an opportunity to the Jute Industry to diversify and capture new market, said Thiru. Dayanidhi Maran, Union Minister of Textiles while launching the International Project for the Development and Application of Potentially Important Jute Geotextiles, on 12th November 2009."
ID: 3896
Publication: BCH Newsletter - January-March 2010
Pages: 15
- 15
Publisher: Business Coordination House (BCH)
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Author: TechTex India Staff
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Jute Fibres in Geosynthetics
The India-based Business Coordination House (BCH), which is involved in, among other things, the creation and promotion of geotextile and other geosynthetic seminars and companies in India, has released its January-March 2010 quarterly newsletter. This issue includes an article on "Jute Fibres in Geosynthetics" from Dr. G.V. Rao (page 42). Read the issue in PDF. He cites transportation and erosion control issues. Drawings are included, as is basic information about geosynthetics.
ID: 3897
Publication: BCH Newsletter - January-March 2010
Pages: 42
- 45
Publisher: Business Coordination House (BCH)
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Author: G.V. Rao
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Performance of Geosynthetic-Encased Stone Columns in Embankment Construction - A Numerical Investigation
This paper presents the results of a numerical investigation into the performance of geosynthetic-encased stone columns installed in soft ground for embankment construction. A three-dimensional finite element model was employed to carry out a parametric study on a number of governing factors such as the consistency of soft ground, the geosynthetic encasement length and stiffness, the embankment fill height, and the area replacement ratio. The results indicate among other things that additional confinement provided by the geosynthetic encasement increases the stiffness of the stone column and reduces the degree of embankment load transferred to the soft ground, thereby decreasing the overall settlement. It is also shown that the geosynthetic encasement has a greater impact for cases with larger stone column spacing and/or weaker soil. Also revealed is that unlike isolated column loading conditions, full encasement may be necessary to ensure maximum settlement reduction when implementing GESCs under an embankment loading condition. Practical implications of the findings are discussed in detail.
ID: 3883
Publication: Journal of Geotechnical and Geoenvironmental Engineering - January 2010
Publisher: ASCE
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Author: Chungsik Yoo
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Required Unfactored Strength of Geosynthetic in Reinforced Earth Structures
Current reinforced earth structure designs arbitrarily distinguish between reinforced walls and slopes, that is, the batter of walls is 20° or less while in slopes it is larger than 20°. This has led to disjointed design methodologies where walls employ a lateral earth pressure approach and slopes utilize limit equilibrium analyses. The earth pressure approach used is either simplified (e.g., ignoring facing effects), approximated (e.g., considering facing effects only partially), or purely empirical. It results in selection of a geosynthetic with a long-term strength that is potentially overly conservative or, by virtue of ignoring statics, potentially unconservative. The limit equilibrium approach used in slopes deals explicitly with global equilibrium only; it is ambiguous about the load in individual layers. Presented is a simple limit equilibrium methodology to determine the unfactored global geosynthetic strength required to ensure sufficient internal stability in reinforced earth structures. This approach allows for seamless integration of the design methodologies for reinforced earth walls and slopes. The methodology that is developed accounts for the sliding resistance of the facing. The results are displayed in the form of dimensionless stability charts. Given the slope angle, the design frictional strength of the soil, and the toe resistance, the required global unfactored strength of the reinforcement can be determined using these charts. The global strength is then distributed among individual layers using three different assumed distribution functions. It is observed that, generally, the assumed distribution functions have secondary effects on the trace of the critical slip surface. The impact of the distribution function on the required global strength of reinforcement is minor and exists only when there is no toe resistance, when the slope tends to be vertical, or when the soil has low strength. Conversely, the impact of the distribution function on the maximum unfactored load in individual layers, a value which is typically used to select the geosynthetics, can result in doubling its required long-term strength
ID: 3884
Publication: Journal of Geotechnical and Geoenvironmental Engineering - February 2010
Vol: 136
Issue: 2
Pages: 281
- 290
Publisher: ASCE
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Author: Dov Leshchinsky, Fan Zhu, and Christopher L. Meehan
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Revegetation Recipe
Planting for erosion control isn’t like tending a garden. The scale of such projects—often covering acres or miles—makes it impossible to give each site the “tender loving care” one might lavish on a favorite flowerbed. Yet the required tasks are somewhat the same; one chooses the right seeds for the site and climate, uses mulch to keep the soil moist and combat weeds, and enriches the soil to make sure it provides the best growing medium. INCLUDES hydraulically-applied erosion control (HECP) products information, such as from Profile Products.
ID: 3863
Publication: Erosion Control - January/February 2010
Publisher: Forester Communications
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Author: Janice Keating
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EPA's Effluent Guidelines: The Final Rule
The editor looks at the effect of new EPA regulations.
ID: 3864
Publication: Erosion Control - January/February 2010
Publisher: Forester Communications
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Author: Janice Kaspersen
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Playing Catch With Mother Nature
Regular contributor Tara Beecham examines inlet and storm-drain protection options that can keep waterways on your site clean and help you meet National Pollutant Discharge Elimination System (NPDES) Phase II requirements.
ID: 3865
Publication: Erosion Control - January/February 2010
Publisher: Forester Communications
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Author: Tara Beecham
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IECA News: IECA Embraces Creative Ideas
In the regular International Erosion Control Association (IECA) column, the writer outlines opportunities at EC10, global activities of IECA, partnerships and more.
ID: 3866
Publication: Erosion Control - January/February 2010
Publisher: Forester Communications
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Author: Julie Etra
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Analysis of Flexible Pavements Reinforced with Geogrids
Effectiveness of glass fiber grids as a reinforcement of the asphalt layer in a flexible pavement system was investigated. The study involved both laboratory experimental work and computer analysis of pavement sections. Twenty flexible pavement sections (with and without glass fiber grids) were constructed and tested in the laboratory as a part of the experimental study. The laboratory-scale pavement sections were instrumented with pressure cells, displacement gages, and strain gages. Test sections were subjected to 1,000,000 load applications at a frequency of 1.2 Hz. Static loading tests were conducted at intervals of 100,000 load applications. In thirteen experiments, glass fiber grids were used as reinforcement in the asphalt layer. Several computer analyses of flexible pavement sections were performed by using the finite element method (FEM). The laboratory data were compared with results obtained from the computer analyses. Results from this study show that glass fiber grids can be used to improve the performance of flexible pavement systems. It was also observed that the inclusion of glass fiber grid in the asphalt layer provided resistance to crack propagation. Overall, the flexible pavement sections reinforced with glass fiber grids showed better performance under laboratory test conditions.
ID: 3855
Publication: Geotechnical and Geological Engineering - Online
Vol: 28
Publisher: Springer Netherlands
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Author: Hema Siriwardane, Raj Gondle, and Bora Kutuk
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