Geotextiles, Geogrids and Geosynthetics

Discrete fiber reinforcement of sands for expedient road construction

Jeb S. Tingle, Steve L. Webster, and Rosa L. Santoni
U.S. Army Corps of Engineers
Technical Report GL-99-3
March 1999

The experiment evaluating the fibre stabilization of sands presented in this report was composed of an extensive laboratory study and two field experiment sections. The entire experiment was conducted during the period May through November 1997 by the U.S. Army Engineer Waterways Experiment Station (WES), Vicksburg, MS. The laboratory experiment was designed to identify the effect of different variables on fibre-stabilized specimens. The field experiment sections were constructed and trafficked to verify the performance of each experiment item when subjected to wheeled military vehicle traffic. A summary of each material investigated and its performance is presented in this report. An analysis of the field data was conducted to determine the potential of these expedient construction materials under actual load conditions. Detailed material information is provided in Chapters 2 and 3 of this report. Chapter 2 describes the laboratory investigation. Chapter 3 presents the field experiments and their results. Conclusions and recommendations are shown in Chapter 4. Tables are incorporated within the individual chapters. Figures and photos follow the report text.

Engineering Use of Geotextiles

UFC 3-220-08FA
16 January 2004

TM 5-818-8, 20 July 1995 (still available)

This manual covers physical properties, functions, design methods, design details and construction procedures for geotextiles as used in pavements, railroad beds, retaining wall earth embankment, rip-rap, concrete revetment, and drain construction. Geotextile functions described include pavements, filtration and drainage, reinforced embankments, railroads, erosion and sediment control, and earth retaining walls. This manual does not cover the use of other geosynthetics such as geogrids, geonets, geomembranes, plastic strip drains, composite products and products made from natural cellulose fibres.

Geosynthetic Design and Construction Guidelines

Robert D. Holtz, Ph.D., P.E.;Barry R. Christopher, Ph.D., P.E.; and Ryan R. Berg, P.E.
FHWA HI-95-038
April 1998

This manual is an updated version of the Geotextile Design & Construction Guidelines, used for the FHWA training course Geosynthetic Engineering Workshop. The update was performed to reflect current practices and codes for geotextile design, and has been expanded to address geogrid and geomembrane materials. The manual was prepared to enable the Highway Engineer to correctly identify and evaluate potential applications of geosynthetics as an alternative to other construction methods and as a means to solve construction problems. With the aid of this text, the Highway Engineer should be able to properly design, select, test, specify, and construct with geotextiles, geocomposite drains, geogrids and related materials in drainage, sediment control, erosion control, roadway, and embankment on soft soils applications. Steepened slope and retaining wall applications also are addressed, but designers are referred to the FHWA Demonstration Project No. 82 references on mechanically stabilized earth structures for details on design. Application of geomembranes and other barrier materials to highway works are summarized within. This manual is directed toward geotechnical, hydraulic, roadway, bridge and structures, and route layout highway engineers.

Geosynthetic Reinforced Soil Integrated Bridge System, Synthesis Report

January 2011

This report is the second in a two-part series to provide engineers with the necessary background knowledge of Geosynthetic Reinforced Soil (GRS) technology and its fundamental characteristics as an alternative to other construction methods. It supplements the interim implementation manual (FHWA-HRT-11-026), which outlines the design and construction of the GRS Integrated Bridge System (IBS). The research behind the proposed design method is presented along with case histories to show the performance of in-service GRS-IBS and GRS walls

Geotextile Reinforcement of Low-Bearing-Capacity Soils: Comparison of Two Design Methods Applicable to Thawing Soils

Karen S. Henry
USACE CRREL Special Report 99-7
June 1997

Thawing fine-grained soils are often saturated and have extremely low bearing capacity. Geosynthetics are used to reinforce unsurfaced roads on weak, saturated soils and therefore are good candidates for use in stabilization of thawing soils. To stabilize the soil, a geotextile is placed on it, then the geotextile is covered with aggregate. Design involves selection of aggregate thickness and geotextile. There are two commonly used design techniques for geotextile reinforcement of low volume roads, and the Army uses one of them. The theory and use of the two design methods for static loading (i.e., up to 100 vehicle passes) are presented and compared in this report. The design method not used by the Army offers the potential to reduce aggregate thickness over the geotextile because it accounts for the fact that the geotextile helps support the traffic load (when in tension) and confines the soil between the wheels and the subgrade. However, this alternative method appears to be unconservative with respect to stresses estimated at the subgrade surface. Thus, the current Army design technique should be used until more research is conducted. In the meantime, straightforward design curves for Army 10- and 20-ton trucks as well as vehicle loading and tire pressure information for a number of other vehicles are included in this report to help make the current design method easy to use. Future work should consider adopting a hybrid design method that provides realistic estimates of stresses at the subgrade and accounts for the tensile properties of geotextiles. In addition, aggregates other than the high quality crushed rock that is inherently assumed by each design method should be accounted for in new design development.

Long-Term Durability of Geosynthetics Based on Exhumed Samples From Construction Projects

V. Elias
FHWA RD-00-157
April 2001

This report presents the results of mechanical and chemical tests on 24 retrieved geosynthetics from 12 sites across the United States and provides a baseline databank of mechanical and chemical properties of many commonly used geosynthetics in transportation applications as tested by industry. It also provides a summary and synthesis of results and methods from site retrievals and comments on the significance of laboratory index testing in developing durability design protocols. This report is the last report of a comprehensive study on the “Durability of Geosynthetic Materials for Highway Applications.”

Performance Test for Geosynthetic-Reinforced Soil Including Effects of Preloading

Kanop Ketchart and Jonathan T.H. Wu
June 2001

A study was undertaken to investigate the behaviour of Geosynthetic Reinforced Soil (GRS) masses under various loading conditions and to develop a simplified analytical model for predicting deformation characteristics of a generic GRS mass. Significant emphasis was placed on the effect of preloading. To conduct the study, a revised laboratory test, known as the Soil-Geosynthetic Performance (SGP) test, was first developed. The test is capable of investigating the behaviour of a generic GRS mass in a manner mimicking the field placement condition, and the soil and geosynthetic reinforcement are allowed to deform in an interactive manner. A series of SGP tests was performed. Different soils and reinforcements were employed, and the soil-geosynthetic composites were subject to various loading sequences. The tests showed that preloading typically reduces vertical and lateral deformations of a generic soil mass by a factor 2 to 7, and that prestressing (preloading followed by reloading from a non-zero stress level) can further increase the vertical stiffness by a factor of 2 to 2.5. Correlations between the results of SGP tests and full-scale GRS structures were evaluated. It was found that the degree of reduction in settlement due to preloading could be assessed by the SGP test with very good accuracy. Finite element analyses were performed to examine the stress distribution in the SGP test. The importance of using small reinforcement spacing was evidenced by the stress distribution. A Simplified Preloading-Reloading (SPR) analytical model was developed to predict the deformation characteristics of a GRS mass subject to monotonic loading and preloading/reloading. The SPR model was shown to be able to accurately predict the results obtained from the SPG tests and numerical analysis of automated plane strain reinforcement (APSR) tests.

Use of Geogrids in Pavement Construction

We also have an older version of this document, ETL 1110-1-188, available for download.

U.S. Army ETL 1110-1-189
14 February 2003

Engineers are continually faced with maintaining and developing pavement infrastructure with limited financial resources. Traditional pavement design and construction practices require high-quality materials for fulfilment of construction standards. In many areas of the world, quality materials are unavailable or in short supply. Due to these constraints, engineers are often forced to seek alternative designs using substandard materials, commercial construction aids, and innovative design practices. One category of commercial construction aids is geosynthetics. Geosynthetics include a large variety of products composed of polymers and are designed to enhance geotechnical and transportation projects. Geosynthetics perform at least one of five functions: separation, reinforcement, filtration, drainage, and containment. One category of geosynthetics in particular, geogrids, has gained increasing acceptance in road construction. Extensive research programs have been conducted by the U.S. Army Engineer Research and Development Centre (ERDC) and non-military agencies to develop design and construction guidance for the inclusion of geogrids in pavement systems. This document describes the use of geogrids in flexible pavement systems including design charts, product specifications, and construction guidance.

Use of Geotextiles Under Riprap

U.S. Army Corps of Engineers
ETL 1110-2-286
25 July 1984

Geotextiles have been used extensively throughout the 234- mile Tennessee-Tombigbee Waterway, primarily to replace multi-layered graded filter systems under the riprap. During the past ten years, the Mobile and Nashville Districts have had considerable experience in placing geotextiles under riprap. Over 4,000,000 square yards of geotextile will have been placed by the conclusion of the Tennessee-Tombigbee Project. Problems were encountered with clogging, tearing, or puncturing of the geotextile and erosion undermining the geotextile. Proper control of both surface and groundwater and close inspection during construction proved to be essential.

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