TRANSPORTATION RESEARCH RECORD No. 1474 Soils, Geology, and Foundations Mechanically Stabilized Backfill and Properties of Geosynthetics and Geocomposites A peer-reviewed publication of the Transportation Research Board TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL NATIONAL ACADEMY PRESS WASHINGTON, D.C. 1995 Sponsorship of Transportation Research Record 1474 Transportation Research Record 1474 ISSN 0361-1981 GROUP 2-DESIGN AND CONSTRUCTION OF ISBN 0-309-06110-5 TRANSPORTATION FACILITIES Price: $27 .00 Chairman: Michael G. Katona, U.S. Air Force Armstrong Laboratory Subscriber Category Soil Mechanics Section IIIA soils, geology, and foundations Chairman: Verne C. McGuffey Printed in the United States of America Committee on Geosynthetics Chairman: Robert K. Barrett, Colorado Department of Transportation Tony M. Allen, Richard J. Bathurst, Ryan R. Berg, Dave Ta-Teh Chang, Barry R. Christopher, James G. Collin, Jerry A. DiMaggio, Victor Elias, David J. Elton, Stephan M. Gale, Deborah J. Goodings, Karen S. Henry, Dov Leshchinsky, James H. Long, Victor A. Modeer, Jr., Bernard Myles, John E. Steward, Fumio Tatsuoka, Steve L. Webster, Jonathan T. H. Wu Geology and Properties of Earth Materials Section Chairman: Robert D. Holtz, University of Washington Committee on Soil and Rock Properties Chairman: Mehmet T. Tumay, Louisiana Transportation Research Center Roy H. Borden, Dario Cardoso de Lima, Umakant Dash, Andrew R. Dawson, Don J. DeGroot, Eric C. Drumm, David J. Elton, Kenneth L. Fishman, An-Bin Huang, Mary E. Hynes, Hilary I. lnyang, Steven L. Kramer, Rodney W. Lentz, Emir Jose Macari, Paul W. Mayne, Kenneth L. McManis, Victor A. Modeer, Jr., Priscilla P. Nelson, Peter G. Nicholson, Norman I. Norrish, John W. Oglesby, Samuel G. Paikowsky, Sibel Pamukcu, Nader S. Rad, Kaare Senneset, Sunil Sharma, Timothy D. Stark, Ramzi Taha Transportation, Research Board Staff Robert E. Spicher, Director, Technical Activities G.P. Jayaprakash, Engineer of Soils, Geology, and Foundations Nancy A. Ackerman, Director, Reports and Editorial Services Sponsorship is indicated by a footnote at the end of each paper. The organizational units, officers, and members are as of December 31, 1994. Transportation Research Record 1474 Contents Foreword v Part 1-Mechanically Stabilized Backfill Texsol: Material Properties and Engineering Performance 3 Phillip Liausu and Ilan Juran Independent Facing Panels for Mechanically Stabilized Earth Walls 13 George Hearn, Scott Myers, and Robert K. Barrett Biotechnical Stabilization of Steepened Slopes 23 Donald H. Gray and Robbin B. Sotir Experiences with Mechanically Stabilized Structures and 30 Native Soil Backfill Gordon R. Keller Retaining Structure Selection at Project Level 39 Timothy G. Hess and Teresa M. Adams Contracting for Mechanically Stabilized Backfill Walls 46 George A. Munfakh Part 2-Properties of Geosynthetics and Geocomposites Survivability and Durability of Geotextiles Buried in Glenwood Canyon Wall 55 f. R. Bell and Robert K. Barrett Pullout Mechanism of Geogrids Under Confinement by Sandy and 64 Clayey Soils Dave Ta-Teh Chang, Tsung-Sheng Sun, and Fan-Yi Hung One-Dimensional Compression Characteristics of Artificial Soils Composed 73 of Multioriented Geosynthetic Elements Evert C. Lawton, James R. Schubach, Richard T. Seelos, and Nathaniel S. Fox Stress-Strain and Strength Behavior of Staple Fiber and 82 Continuous Filament-Reinforced Sand S. D. Stauffer and R. D. Holtz Influence of Geosynthetic Reinforcement on Granular Soils 96 I. Ismail and G. P. Raymond Limit Condition for Fiber-Reinforced Granular Soils 102 Radoslaw L. Michalowski and Aigen Zhao Reinforcement of Fissured Clays by Short Steel Fibers 108 Luis E. Vallejo and Hankyu Yoo Foreword The 13 papers included in this volume are arranged into two general groups. The first group consists of papers that are related to mechanically stabilized backfill (MSB) materials. These papers focus on ad­ vanced technologies related to MSB and on ownership roles in providing support during the design and construction phases. These papers also discuss performance of MSB applications using case histories. The second group of papers is on properties of geosynthetics and geocomposites. These papers include information on the long-term durability of geosynthetics used as soil reinforcements; the frictional mechanism of geogrid-soil systems on the basis of results from tests on different types of geogrid-soil combinations; and the properties of granular and clayey soils that are reinforced using multioriented geosynthetic elements, staple fiber, continuous filament, and synthetic and steel fibers. v PARTl Mechanically Stabilized Backfill TRANSPORTA.TION RESEARCH RECORD 1474 3 Texsol: Material Properties and Engineering Performance PHILLIP LIAUSU AND !LAN JURAN Texsol is a composite material made of sand and continuous polyester earth retaining walls, particularly on soft compressible soils, with fibers mixed together in situ to form a homogeneous construction mate­ facing slope angles of 65 to 75 degrees; stabilization of earth slopes rial. The fiber content varies between 0.1 and 0.2 percent of the weight in cuts and embankments; steepening of existing slopes for widen­ of sand. The fibers provide for the high cohesion of Texsol and its abil­ ing of motorways; surface protection of man-made and natural ity to sustain large strains without degradation of its mechanical slopes against rock falls and surface erosion due to climate condi­ properties. The sand is well-graded medium course material and pro­ vides for the internal friction resistance of Texsol and its self-draining tions (e.g., freezing temperature); and explosion-resistant facilities characteristics. Substantial testing programs have been conducted by in civil and military installations for storage of explosives and state agencies, universities, and research institutions in France and liquefied gas, offering a remarkable market potential for civil engi­ subsequently in Japan to assess the engineering performance of this neering construction in earthquake zones. composite material and develop relevant design methods for its various This paper presents the main results of the research conducted to fields of application. assess the material properties and engineering performance of Texsol' s structural applications. Texsol is a composite material made of sand and continuous polyester fibers mixed together in situ to form a homogeneous con­ struction material. The fiber content varies between 0.1 and 0.2 per­ MATERIAL PROPERTIES cent of the weight of sand. The fibers provide for the high cohesion of Texsol and its ability to sustain large strains without degradation Sheer Strength Characteristics of its mechanical properties. The sand is well-graded medium course material and provides for the internal friction resistance of The mechanical properties of Texsol depend on the characteristics Texsol and its self-draining characteristics. of the granular material used, thread type, fiber content, production Substantial testing programs have been conducted by state agen­ equipment, and compaction parameters (density and water content). cies, universities, and research institutioµs in France and subse=­ Figure 2 shows the results of triaxial compression tests performed quently Japan to assess the engineering performance of this com­ on samples of Texsol and unreinforced sand under different confin­ posite material and develop relevant design methods for its various ing pressures and the related characteristic failure curves of these fields of application. The research and development programs, as materials. Test results illustrate that the shear modulus of Texsol well as field observations on more than 100 Texsol structures con­ and its hydraulic conductivity are similar to that of the natural sand. structed since 1984, demonstrated that the engineering properties of The main mechanical properties of Texsol are Texsol include high shear resistance with anisotropic mechanically built-in internal cohesion and internal friction angle that are depen­ • Unconfined compressive strength: 500 kPa/0.1 percent of fill dent on the fiber content (1,2), self-draining properties of the sand content ratio by weight; used, low creep potential under normal operating conditions, dura­ • Apparent cohesion of 100 kPa/0.1 percent of fill content ratio bility and sustainable resistance to chemical and biological attacks, by weight; high ductibility and large energy absorption capacity with high • Internal friction angle that is equal or greater than that of the resistance to impact, explosions, and seismic effects (3,4); deforma­ natural sand, with bility and large tolerance to differential settlements; high resistance 0 Texsol = 0 soil + Ll0, to runoff surface erosion (5), and high thermal resistance under (Ll 0 varies from 0 to 10); fire-generated heat up to 600°F (6). In addition, Texsol provides a • Yield strain that is greater than that of the natural sand, indi­ suitable support for plant roots to penetrate and seeds to germinate. cating the ductile behavior of Texsol with Mixed in organic soil, fertilizer, and seeds, the Texsol green method £Texsol = £soil + LlEr enables the hydroseeding of steep natural slopes, excavated slopes, (LlE varies from 0 to 10 percent); embankments, retaining walls, soundproof walls, and so forth, where conventional hydroseeding techniques are impractical. Because of the production process of Texsol, the shear strength Because of its remarkable features, Texsol has been increasingly