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18TH STREET PEDESTRIAN IMPROVEMENTS 3741 RMT July 03, 2024 72 Sieve Size Percent Passing 1” (25 mm) 100 3/4" (19 mm) 100 – 75 No. 4 (4.75 mm) 0 - 10 No. 50 (300um) 0 – 5 1 8-26.2(5) Geogrid Soil Reinforcement 2 Geogrid Soil Reinforcement: a structural element formed of high tenacity woven/ 3 knitted polyester yarns or high-density polyethylene (HDPE) into a regular network of 4 integrally connected tensile elements with apertures of sufficient size to allow 5 interlocking with surrounding soil, rock, or earth and function primarily as 6 reinforcement. 7 8 Geogrid soil reinforcement shall consist of Geotextile for Retaining Walls and 9 Reinforced Slopes per WSDOT Standard Specification 9-33.2(2) Table 7. 10 11 8-26.2(6) Reinforced Backfill 12 13 Reinforced Backfill: compacted soil that is placed within the reinforced soil volume as 14 outlined on the plans. 15 16 Reinforced backfill shall be free of debris and organic material; meeting the following 17 gradation tested in accordance with ASTM D422: 18 Sieve Size Percent Passing 3/4" (19 mm) 100 – 75 No. 40 (425um) 0 - 60 No. 200 (75um) 0 – 35 19 Plasticity Index (PI) <15 and Liquid Limit (LL) <40 per ASTM D4318. 20 21 The maximum aggregate size shall be limited to 3/4" (19 mm) unless field tests have 22 been performed to evaluate potential strength reductions to the geogrid design due to 23 damage during construction. 24 25 Material can be site-excavated soils where the above requirements can be met. 26 Unsuitable soils for backfill (high plastic clays or organic soils) shall not be used in the 27 backfill or in the reinforced soil mass. 28 29 Contractor shall submit reinforced backfill sample and laboratory test results to the 30 Engineer for approval prior to the use of any proposed reinforced fill material. 31 32 33