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PN: 50663GE <br />November 20, 2006 <br />Retaining wall zone <br />of influence <br />Retaining <br />Structure Impervious soil <br />backfill for <br />upper 2 feet <br />55 Degrees <br />Retaining Structure Zone of <br />Influence Concept, No Scale <br />If a granulaz backfill is chosen it should not extend to the ground surface. Some granulaz soils <br />allow ready water migration which may result in increased water access to the foundation soils. <br />The upper few feet of the backfill should be constructed using an impervious soil such as silty- <br />clay and clay soils from the project site, if these soils aze available. <br />Backfill should not be placed and compacted behind the retaining structure unless approved by <br />the project structural engineer. Backfill placed prior to construction of all appropriate structural <br />members such as floors, or prior to appropriate curing of the retaining wall concrete (if used) may <br />result in severe damage and/or failure of the retaining structure. <br />6.1 Mechanically Stabilized Earth (MSE) Structures <br />Mechanically stabilized earth (MSE) structures aze becoming more commonly used retaining <br />structures, particularly for exterior areas. MSE structures generally consist of compacted earth <br />which is interbedded with geotextile fabric and a wall face. There aze numerous proprietary <br />MSE systems currently available. Each MSE system typically has design criteria specific to their <br />product. A relatively common specification is the use of granular soil fill for the structure. <br />Granulaz soils, those that have a sandy matrix, perform better in MSE structure than do cohesive <br />soils, such a clays. Granular soils develop much high frictional forces when in contact with the <br />geotextile fabric. Higher frictional forces will help provide a more stable structure. <br />It is imperative that proper and thorough compaction of the fill material within the MSE <br />structure be achieved for proper performance of the system. Failure of MSE structures which do <br />not have properly compacted fill material may occur. <br />16 TRAUTNER ~ <br />A DIVISION OF TRIGONH~d <br />