1208 50TH ST SW 2017-01-27 - Laserfiche WebLink

' SF�ECIFICATIONS FOR REINFORCED WALL General ' 1. The contractor shall have an approved set of plans and specifications on site at all times during the construction of the wall. The wall layout is the responsibility of the contractor. 2. Nelson Geotechnical Associates (NGA) shall observe and monitor the construction of the wall on a full-time basis. 3. Stratagrid geogrid or equivalent shall be used for this project. All geogrid and facing materials shall be approved by NGA ' prior to installation. 4. The contractor may use longer geogrid lengths than the design sections for ease of construction. The geogrid lengths may not be shorter unless approved by NGA. ' Subqrade Preparation 1. The ground shall be prepared by removing surficial organics, loose soil and undocumented fill to expose competent soils as approved by NGA. 2. Exisitng utilities shall be located and their depths varified in the field. If utility trenches or undocumented fill are encountered ' within the wall or reinforced fill subgrade, the subgrade shall be prepared as recommended and approved by NGA. 3. A generally level bench with a minimum width equal to the design length of the geogrid is required for placement of the reinforced fill. The surface of the level benches should be compacted to an unyielding conditions approved by NGA. 4. The excavation shall be cleaned of all excess material and protected, as necessary, from construction traffic to maintain the ' intergrity of the subgrade. 5. The base of the excavation should be deep enough to satisfy a minimum embedment of 1.5 feet. If the wall foundation subgrade exposes undocumented fill soils, these soils should be overexcavated by a minimum 1.0 feet and replaced with 1-1/4 inch crushed rock. ' 6. The excavation walls shall be sloped back at 2H:1V for safety. If this is not feasible, specific recommendations for maintaining excavation stability shall be provided by NGA. All WISHA/OSHA safety requirements shall be observed at all times during construction. Geoqrid Placement ' 1. The reinforcement shall be rolled out, cut to length, and laid at the proper elevation, location, and orientation. Orientation of the reinforcement is of extreme importance since geogrids vary in strength with roll direction. The contractor shall be responsible for the correct orientation. 2. Geogrid shall be placed at the location and elevations shown on the plans. The geogrid length is measured from the back of ' the blocks. 3. Prior to placing the fill, the geogrid shall be pulled to remove the slack and stretched by hand until taut and free of wrinkles. Fill Placement ' 1. Structural fill, consisting of granular import soils or granular on-site material no greater than 3 inches in size, shall then be placed upon the subgrade and geogrid. If larger rock is used in the fill, additional layers of geogrid may need to be used in the reinforcement. The contractor shall prevent damage to the geogrid by placing the first lift of structural fill with at least a 1-foot thickness. NGA shall approve materiai placed in the reinforced zone, before placement. ' 2. Structural fill shall have parameters equal to or better than those stated for the reinforced wall fill befow with less then 20 percent passing the number 200 sieve. NGA may allow a higher silt content based on review of the wall design and proposed fill parameters. 3. Soil density tests shall be performed as designated by NGA. ' 4. Fill soils in the wall area shall be compacted to at least 95 percent of the Maximum Dry Density (MDD) as determined by ASTM D-1557. 5. The soil shall be placed in relatively uniform horizontal lifts not exceeding 10 or 12 inches in thickness. The lift thickness shall not exceed the manufacturer's recommended depth for the compactive device used on the project. ' 1 ' Drainage 1. A specific drainage system is shown on the plans. Alternative drains can be used based on conditions found in the field and the material used within the reinforced zone. Changes to the drainage system should be approved by NGA prior to placement. 2. A drainage blanket 12 inches in width shall be installed directly behind the block facing and shall consist of 2-inch clean crushed rock. All of the drainage materials shall have a fines content no greater than 5 percent passing the number 200 sieve. A 4-inch rigid perforated pipe embedded in a minimum of one foot of pea gravel or washed rock and wrapped with filter fabric shall be installed at the bottom of the drainage layer 3. Surface water shall not be allowed to pond in or near the reinforced fill zone during or after construction. 4. Suitable clean-outs shall be installed every 50 feet for future maintenance. 5. Surface water shall not be allowed to reach the drainage layer. Desiqn Parameters , Reinforced Wall Fill: 32 degrees, 0 PSF, 120 PCF Retained Backfill: 32 degrees, 0 PSF, 120 PCF Foundation Soil: 32 degrees, 0 PSF, 120 PCF Internal Stability of Wall Minimum Factor of Safety o� Geogrid Strength: 1.5 Minimum Factor of Safety on Geogrid Puilout: 1.5 Soil-Geogrid Interaction Coefficient: 1.0 Percent Coverage of Geogrid: 100 Percent ' External Stability of Wall Minimum Factor of Safety against Base Sliding: 1.5 Inspection Minimum Factor of Safety against Overturning: 2.0 Wall construction shall be completed under the Minimum Factor of Safety against Bearing Capacity: 2.0 direction of NGA. ' C� Retained Soil Approximate Limits of Excavation Level Benches 8" Min. Low Permeable Soil �� Stratagrid Geogrid o/quilvalent � Reinforced Soil Approximate Limits of Excavation Retained Soil IMinimum Horizontal Separation of 20 teet I I Keystone Cap Unit Keystone 21.5 -inch Standard Unit o at 14V:1 H batter � Unit Drainage Fill (3/4" � Crushed Rock or Stone) �° � � L m � x 8" Min. Low Permeable Soil - � � m Max. Siope �6.H � I Crushed Rock _ Reinforced Soil Grid Depth (See Table Below) Firm Foundation Soil (to be approved by NGA pnor to installation) *Nate: Minimum wall embedment shall be a minimum of 1.5 feet. Wall foundation subgrades should be overexcavated by a minimum 1.0 feet, compacted to an unyielding condition and 1-1/4-inch crushed rock should be compacted in the overexcavation. Keystone Cap Unit Keystone 21.5 -inch Standard Unit at 14V:1 H batter Unit Drainage Fill (3/4" Crushed Rock or Stone) Minimum embedment '(see note below) Finished Grade Unreinforced Concrete or Crushed Stone Leveling Pad Wall subgrade to be verified in the field and prepared in accordance with NGA recommendations. 4" Perforated PVC Pipe Tightlined to Discharge at toe of slope **SG200: Stratagrid 200 Geogrid, or equivalent details\ Ke storn Y � U Y �, m m � C f!J m •; c � rn � O d � r tv M � � J 'a Z _ W '" � ,Wn V Z � J W Z � WL r U � � � d Z 4 � Z N � N (9 � J O 'Wn V a�S � � W W Z � z W J a U Z _ U W N 0 W � Y U O m a� � U � U � O � C - � � � � � 0 .� � � � .� � � � � t Q � O .� � � N Y N � � N � � z co U CO � � O � �� � N M � U �, �, _ � � o � � �, �� OL N UU� N � c a� 3 E o 3 o � 3 L C O � ��