<p><p><figure id='attachment_2577' style='max-width:435px' class='caption aligncenter'><img class="wp-image-2577 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a soil mixer behind a tractor mixing fibers in a clay soil." width="435" height="285" /><figcaption class='caption-text'> Mixing of fibers with soil in field (Photograph courtesy of U.S. Army Corps of Engineers).</figcaption></figure><h2>Basic Function:</h2>Discrete Fibers are mixed with soil to increase soil shear strength, CBR, ductility, and rut resistance.<br><h2>Advantages:<em> </em></h2><ul> <li>Reduce the rutting deformation of the pavement.</li> <li>Increase the life of unpaved and paved roads and reduce the required base thickness.</li></ul><h2>General Description:</h2>Fiber reinforcement consists of synthetic or natural fibers reinforcing a fiber soil matrix. Synthetic fibers are generally polypropylene while natural fibers can consist of coir, sisal, or other available fibers. Fibers have been mixed with sand, cement-modified silty sand, and lime modified high plasticity clays. Fibers soil matrix can be mixed in a mill and placed, or the fibers can be mixed into the soil with a traveling rotary mixer. The improved soil matrix is dependent on the existing soil, fiber type, fiber length, fiber content. Fiber reinforcement enhances the system performance and life expectancy of the pavement by increase soil shear strength, CBR, ductility, and rut resistance.<br><h2>Geologic Applicability<strong>:</strong></h2><ul> <li>Fiber reinforcement is generally used with cohesionless soils.</li> <li>Fiber reinforcement when used with cohesive soils, are included with cement or lime stabilization.</li></ul><h2>Construction Methods:</h2>During construction, the fibers are mixed in place to a specified depth with a rotary mixer, or the soil is excavated, the fibers are mixed in a mill, and the matrix is filled in place. In some soil conditions cement or lime may be mixed also. Then the mixed material has to be compacted to the desired density.<br><h2>Additional Information:</h2>Mixing fibers is time consuming and it is difficult to achieve uniformity. This technology is not suitable for rapid renewal The key obstacles preventing more wide-spread use of this technology are: (1) lack of design method; (2) lack of QC/QA methods, (3) limited documented case histories. Fiber reinforcement has shown the ability to reduce shrinkage, swelling and liquefaction.<br><h2>SHRP2 Applications:</h2><ul> <li>Embankment Widening</li> <li>Stabilization of Working Platforms</li></ul><h2>Example Successful Applications<strong>:</strong></h2><ul> <li>Contingency Airfield and Road Construction Using Geosynthetic Fiber Stabilization of Sands, Army Engineer Waterways Experiment Station Vicksburg</li> <li>Strength and Life of Stabilized Pavement Layers Containing Fibrillated Polypropylene, Texas Transportation Institute</li> <li>Rapid Assessment of Cement and Fiber-Stabilized Soil using Roller-Integrated Compaction Monitoring</li></ul><h2>Complementary Technologies:</h2><ul> <li>Mechanical or chemical stabilization.</li></ul><h2>Alternate Technologies:</h2>Geogrid reinforcement, Geocell reinforcement, thicker unreinforced base/subbase, lime or cement-stabilized subgrade, over-excavation and replacement of subgrade.<br><h2>Potential Disadvantages:</h2><ul> <li>Limited test data for long-term performance.</li> <li>Lack of simple, comprehensive analysis and design procedures.</li> <li>Limited demonstration of life-cycle cost benefits.</li> <li>Limited QC/QA methods.</li> <li>Limited documented case histories.</li> <li>Difficulty in evenly mixing fibers in soil.</li> <li>Technology not suitable for rapid renewal.</li></ul><h2>Key References for this technology:</h2>Crockford, W. W., Grogan, W. P., and Chill, D. S. (1993). "Strength and life of stabilized pavement layers containing fibrillated polypropylene." <em>Transportation Research Record </em>1418, Transportation Research Board, Washington, DC, 60–66</p><p>Grogan, W. P., Johnson, W. G., and Army Engineer Waterways Experiment Station Vicksburg Ms Geotechnical, L. A. B. (1994). "Stabilization of High Plasticity Clay and Silty Sand by Inclusion of Discrete Fibrillated Polypropylene Fibers (Fibergrids) (trade name) for Use in Pavement Subgrades". City: Defense Technical Information Center: Ft. Belvoir.</p><p>Tingle, J. S., Santoni, R. L., and Webster, S. L. (2002). "Full-Scale Field Tests of Discrete Fiber-Reinforced Sand." <em>Journal of Transportation Engineering</em>, 128(1), 9-16.</p><p>&nbsp;</p><p>&nbsp;</p></p>