Laserfiche WebLink
18TH STREET PEDESTRIAN IMPROVEMENTS 3741 RMT July 03, 2024 75 The geogrid shall be laid horizontally on compacted reinforced backfill and attached 1 to the CMB wall units. Place the next course of CMB units over the geogrid. The 2 geogrid shall be pulled taut and anchored prior to backfill placement on the geogrid. 3 4 Geogrid soil reinforcement shall be continuous throughout their embedment lengths 5 and placed side-by-side to provide 100% coverage at each level. Spliced connections 6 between shorter pieces of geogrid or gaps between adjacent pieces of geogrid are 7 not permitted. 8 9 8-26.3(6) Reinforced Backfill Installation 10 Place and compact reinforced backfill behind CMB units and unit drainage fill. Follow 11 wall erection closely with reinforced backfill. Reinforced backfill shall be placed, 12 spread, and compacted in such a manner that minimizes the development of slack in 13 the geogrid and installation damage. 14 15 Reinforced backfill shall be placed and compacted in lifts not to exceed 6 inches 16 where hand operated compaction is used, or 8 – 10 inches where heavy self-propelled 17 compaction equipment is used. Lift thickness shall be decreased to achieve the 18 required density, as needed. 19 20 Reinforced backfill shall be compacted to a minimum of 95% Standard Proctor density 21 per ASTM D698 or 92% Modified Proctor Density per ASTM D1557. The moisture 22 content of the backfill material prior to and during compaction shall be uniformly 23 distributed throughout each layer. 24 25 Only lightweight hand operated equipment shall be allowed within 3 feet (1 m) from 26 the tail of the CMB unit retaining wall. 27 28 Tracked construction equipment shall not be operated directly upon the geogrid 29 reinforcement. A minimum reinforces backfill thickness of 6 inches is required prior to 30 operation of tracked vehicles over the geogrid. Tracked vehicle turning should be kept 31 to a minimum to prevent tracks from displacing the reinforced backfill and damaging 32 the geogrid. 33 34 At the end of each day's operation, the Contractor shall slope the last lift of reinforced 35 backfill away from the CMB units to direct runoff away from wall face. The Contractor 36 shall not allow surface runoff from adjacent areas to enter the wall construction site. 37 38 8-26.3(7) Bond Breaker Geotextile 39 Before placing bond breaker geotextile, remove foreign and loose materials from 40 base. Place bond breaker geotextile less than 72 hours before covering it with 41 pavement. Except when pavement is placed against previously placed pavement, 42 extend the bond breaker at least 6 inches beyond the limits of the planned concrete 43 placement. 44 45 Place bond breaker geotextile in a wrinkle free manner. Overlap adjacent sheets a 46 minimum of 8 inches in the same direction as the concrete pour. Overlap no more 47 than three layers at any location. Secure the bond breaker sufficiently that it remains 48 in place during concrete placement. Ensure that no concrete will get under the bond 49 breaker. Fastener spacing of 6 feet in the field and 3 feet along edges is recommended 50 in order to prevent fabric displacement. 51 52