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MECHANICALLY REINFORCED EARTH FILLS <br />Backfill soils for Slo~~e Retention <br />purposes shall be within the gradational and plasticity limits <br />shown in the ROAD FILL MATERIALS section of this report, Sandy <br />Gravel & Cobble Colluvium and Alluvium GM (Soil Type 11. For Road <br />Fills, the Clayey Gravel Colluvium CL (Soil Type 21 may be used. <br />Soft and deleterious materials shall not be used. Ph of the <br />backfill shall not be Less than 3 or greater than 12. <br />Biaxial Geogrid for mechanical rein- <br />forcement shall have a minimum tensile strength @ 5X strain of <br />650 lb/Pt., in the weakest directions (such as Tensar BX 1200 or <br />Miragrid 5T ). <br />The subgrade soils shall be cut, pre- <br />pared and compacted as described in the PLACING and COMPACTING <br />FILL section of this report. The base layer of fill shall be <br />placed at a compacted thickness of 8 to 12 inches. The Lowest <br />layer of the Geogrid shall be place on the compacted fill sur- <br />face, beginning at the 'face' of the fill and extending in the <br />full width of the fill. <br />The compacted fill thickness above each <br />Geogrid layer shall be a minimum of 4 inches. Equipment tires or <br />tracks shall not be allowed on any fills less than 4 inches thick <br />above the Geogrid. Turning of vehicles on the first fill lift <br />shall not be permitted.. Compaction equipment shall not have <br />protrusions greater than 1/2 the minimum fill thickness 14 inch <br />minimum fill; therefore 2" minimum roller protrusionl, to protect <br />the Geogrid. <br />11 <br />