aggregate filters (Dunham and Barrett, 1976], and permit the use of larger 

 stones adjacent to the filter, thereby possibly reducing the overall thick- 

 ness of the structure (Barrett, 1966; Dunham and Barrett 1976) . When armor 

 is removed or rearranged, the fabric's independent strength should also 

 retain the soil (Barrett, 1966; Fairley, et al., 1970) and prevent cavity 

 formation. 



2_ Elongation at Failure . This is part of the tensile test 

 described in Appendix C. Percent of elongation must be known because exces- 

 sive elongation will distort and enlarge the pores and change the soil 

 retention capabilities (piping resistance) (Steward, Williamson, and Mahoney, 

 1977). If excessive elongation is necessary to develop the fabric's ultimate 

 strength, the fabric will probably never develop its required strength in- 

 situ. 



_3_ Seam Strength . It is advantageous to use geotextile 

 filter sheets or panels in large lengths and widths in most applications. 

 The larger panels reduce the number of overlaps required which is the most 

 probable cause for error during construction. Fabrics are manufactured in 

 various widths 1.8 to 5.2 meters (6 to 17 feet), and then sewn together or 

 bonded by cementing or by heat to form large panels as much as 25.6 meters 

 (84 feet) wide. When sections are sewn together the yarn used must conform 

 to the chemical requirements in subparagraphs 2b and 4b. If the seam strengths 

 are too low the sheets may separate and permit piping to develop. 



4_ Puncture Resistance . Puncture resistance is required 

 to enable the geotextile filter to survive placement of other materials on 

 it during the construction process and to prevent rupture or penetration by 

 the overlying material when the structure is exposed to wave action. 



5 Burst Strength . Burst strength must be considered to 

 assure the engineer that the fabric will retain its integrity when subjected 

 to earth forces especially when the material above it contains relatively 

 large voids. 



6_ Abrasion Resistance . In all types of use, abrasion 

 resistance is important during construction. In one case, fabric was 

 damaged during construction of a French drain merely by placing small 

 filter aggregate into the trench it lined. In coastal structures such as 

 revetments, abrasion resistance is required not only during construction 

 but also throughout the life of the structure, for these structures are 

 subjected to continuous or intermittent wave attacks which result in 

 movement of the overlying material adjacent to the fabric. 



(b) Optional Requirements for Special Site Conditions . In 

 certain climatic conditions and geographic locations, it may be desirable to 

 test the geotextile for freeze-thaw resistance, high temperature surviv- 

 ability, and low temperature survivability. When soils in the project site 

 are contaminated, or are subject to infiltration, by high quantities of 

 acids, alkalies, or JP-4 fuel, it may be advisable to test the geotextile's 

 resistance to the specific contaminant. Test methods are described in 

 Appendix C. 



(c) Properties Required for Construction Conditions . The 

 physical properties of geotextiles required for specific sites and structures 



I 



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