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Koerner R.M.,Drexel University | Koerner G.R.,Geosynthetic Institute
Journal of GeoEngineering | Year: 2011

Mechanically stabilized earth (MSE) walls reinforced by geogrids and geotextiles have seen a tremendous growth over the past thirty years. However, along with this growth has come numerous failures consisting of excessive deformation and, in some cases, actual collapse. Of the 82-cases in the authors data base, improper drainage control was the cause in 68% of them. As a result, this paper is focused on both internal drainage issues within the reinforced soil mass within the reinforced soil mass (46%) and external drainage issues around the soil mass (22%). After a brief introduction of the technology some elements of traditional design will be presented. The issue of proper versus improper methods of drainage control will then form the core of the paper. A summary and recommendations section aimed at preventing drainage problems in the future will conclude the paper. Source


Wong W.-K.,Geosynthetic Institute | Hsuan Y.,Drexel University
Transportation Research Record | Year: 2012

This paper presents the interaction between carbon black and antioxidants in high-density polyethylene. The 11 formulations prepared for this study were composed of furnace black with particle sizes of 27 and 75 nm at 2% to 5% by weight and different concentrations of antioxidants Irganox 1010 and Irgafos 168. The chemical interactions between the carbon black and the antioxidants were accelerated by elevated temperatures of 85 C in a forced-air oven. The relative amount of antioxidants retained in the samples throughout the incubation was measured using the oxidative induction time (OIT) test. The results showed that the initial OIT value increased with the weight percentage of the carbon black in the sample. A higher initial OIT value was found in the samples that had been blended with the 27-nm carbon black than in those blended with the 75-nm carbon black at the same concentration. Also, faster OIT depletion was detected in the samples that had been blended with the 27-nm carbon black than in those blended with the 75-nm carbon black at greater than 2% by weight. The carbon black-antioxidant interaction was found to be influenced by the carbon black-specific surface area and physical structure. Overall, the OIT decreased substantially faster in the samples with carbon black than in those without it. The reactions between the carbon black and the antioxidants were so strong that only a minor difference in the depletion rate was observed between the two antioxidant formulations. Source


Koerner R.M.,Drexel University | Koerner G.R.,Geosynthetic Institute
Geotechnical Testing Journal | Year: 2010

There are two performance tests available for the selection of fabrics and additives when contemplating a geotextile bag, container, or tube application. They are the "hanging bag test" and the "pillow test." Both tests are described in this paper along with data generated by their use. While both can be used for selection purposes, the advantages of the pillow test over the hanging bag test are quite compelling. Items favoring the pillow test are much smaller size, need for less dredged or slurried infill material, better field simulated orientation, and the capability of monitoring hydraulic head versus time behavior. This last item is most important since dredging pressures are always involved and the simulated behavior of the pillow test gives good insight into the anticipated behavior of the full-scale application. Copyright © 2010 by ASTM International. Source


Koerner G.R.,Geosynthetic Institute | Koerner R.M.,Drexel University
Geotextiles and Geomembranes | Year: 2011

It is common practice to use needle-punched nonwoven geotextiles as puncture protection for geomembranes against sharp objects like gravel or stones in either the soil above or the underlying soil/rock below. There are several design and experimental methods available for geotextile selection in this regard. None, however, directly address the type of resin or fiber from which the geotextile is made. This paper does exactly that insofar as a direct comparison of similar mass per unit area polyester (PET) versus polypropylene (PP) geotextiles are concerned. Furthermore, two types of PP geotextiles are evaluated; one made from continuous filaments and the other from staple fibers. Three different size and shaped puncture probes are used in the testing program. All three are ASTM Standards, i.e., D4833, D5495 and D6241. The test results clearly indicate that geotextiles made from PP fibers outperform those made from PET fibers at all masses evaluated. Clearly, the present trend of using PP resin for heavy nonwoven protection geotextiles seems justified on the basis of these test results. In addition, the continuous filament PP and staple fiber PP geotextiles performed equivalently over all mass ranges for the three different types of puncture tests. © 2010 Elsevier Ltd. Source


Koerner R.M.,Drexel University | Hsuan Y.G.,Drexel University | Koerner G.R.,Geosynthetic Institute | Gryger D.,Gannett Fleming Inc.
Geotextiles and Geomembranes | Year: 2010

The need for a geotextile to be used for protection against geomembrane puncture by stones and gravel has been recognized for many years. There are presently several methods available for selecting such geotextiles. This paper, however, focuses on the " GRI-Method" , which was originally based on short-term tests and was extended empirically for long-term performance. The reduction factor for creep behavior (RFCR) is of particular interest since its impact on the resulting geotextile design is the greatest.The paper presents results of a 10-year long creep puncture study which is configured exactly the same as was the original short-term testing program. The results indicate that the six ≈38. mm high puncturing cones result in yield of the geomembrane at pressures of 34 and 52. kPa and one even had a small break. The six 12. mm high cones at pressures of 430 and 580 kPa also resulted in geomembrane yield but only by a nominal amount and there were no breaks.As a consequence of these creep test results, the original table for creep reduction factors (RFCR) has been revised into more conservative values. In this regard, the originally published RFCR table should be replaced accordingly. © 2010 Elsevier Ltd. Source

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