241 ALASKA 2020 SECTION 511 MECHANICALLY STABILI ZED EARTH (MSE) WALL
511-1.01 DESCRIPTION . Furnish and install mechanically stabi lized earth wall.
511-2.01 MATERIALS. Meet the following:
Class A Concrete Section 501 Precast and Cast -in-Place Concrete Panels Section 501 Reinforcing Steel Section 503 Structural Steel AASHTO M 270 Pipe and Perforated Pipe Section 706 Geotextile for Drainage Subsection 729- 2.02 Geogrid Subsection 729- 2.05 Geocomposite Drainage System As Specified Porous Backfill Material Subsection 703- 2.10
1.Structure Backfill and Foundation Fill . Meet Subsection 703- 2.07, Selected Material, Type A. Use materials wi th a sodium sulfate soundness loss less than 30 percent after four cycles as determined by AASHTO T 104 and free of shale or other particles of low durability. When using backfill material with 80 percent passing the 3/4 inch sieve, the minimum angle of in ternal friction on the portion of the material finer than the No. 10 sieve must be 34 degrees, as tested by AASHTO T 236. When using steel soil reinforcement, use backfill material meeting the following electrochemical requirements:
a.pH of 5 to 10 (AASHTO T 289)
b.Resistivity not less than 30 ohmmeters (AASHTO T 288)
c.Chlorides not greater than 100 ppm (AASHTO T 291)
d.Sulfates not greater than 200 ppm (AASHTO T 290)
2.Wall Members . Provide facing consisting of precast concrete panels, modular units, cast -in- place concrete, or welded wire fabric, as specified. Manufacture concrete panels with a minimum concrete compressive strength of 4,000 psi. Finish the exposed face with ordinary finish. For the face not exposed to view, provide a uniform surface finish free of open pockets of aggregate or surface distortions in excess of 1/4 inch. Locate soil reinforcement connection hardware during concrete placement to avoid contact with the panel reinforcing steel. Shop- fabricate welded wire fabric reinforcement from cold-drawn wire meeting AASHTO M 32, and the finished fabric meeting AASHTO M 55.
3.Soil Reinforcement . Use approved geogrid reinforcement. Galvanize all steel soil reinforcement and any steel connection hardware to meet AASHTO M 111. Manufacture steel strip reinfor cement by hot rolling to meet ASTM A572, Grade 450, or approved alternate.
4.Working Drawings . Submit all working drawings and design calculations, including:
a.Earthwork requirements including specifications for material and compaction of backfill.
b.Details of revisions or additions to drainage systems or other facilities required to accommodate the system. 242 ALASKA 2020 c. Existing ground elevations verified by the Contractor for each location involving construction wholly or partially in original ground.
d.Complete design calculations substantiating that all proposed designs satisfy the design parameters in the Contract documents.
e.Complete details of all elements required for the proper construction of the system, including complete material specifications. Prohibit work on eart h retaining systems for which working drawings are required until such drawings have been approved.
511-3.01 Constructio N.
2.Drainage. Provide outlet works at sags in the profile and at the low ends of the gutter.
a.Weep Holes . Place a minimum of 2 cubic feet of porous backfill mat erial encapsulated with geotextile at each weep hole. Cover joints between retaining wall panels, which function as weep holes, with geotextile. Dry and thoroughly clean the face panels that are to receive the geotextile.
b.Drainage Blankets . Construct drainage blankets consisting of porous backfill material encapsulated in geotextile, collector pipes, outlet pipes, and cleanout pipes. Construct and compact the subgrade to receive the geotextile so it is free of loose or extraneous material and sharp objects that may damage the geotextile. Stretch, align, and place the fabric in a wrinkle -free manner. Overlap adjacent borders of the fabric from 12 to 18 inches. Repair torn or punctured fabric by covering the damaged area with a piece of fabric large enough to cover the damaged area and meet the overlap requirement. Place the porous backfill material in horizontal layers and thoroughly consolidate by the same methods specified for structure backfill. Prohibit ponding or jetting of porous backfill material or str ucture backfill material. Maintain a minimum of 6 inches of porous backfill material , structure backfill, or embankment material between the fabric and the equipment during spreading and compaction of the porous backfill material . Place perforated collector pipe, when required, within the porous backfill material to the flow line elevations shown. Place outlet pipes at sags in the flow line and at the low end of the collector pipe. Construct rock slope protection, when required, at the end of outlet pipes, as shown on the Plans. Place cleanout pipes at the high ends of collector pipes.
c.Geocomposite Drainage Systems . Place and secure the geocomposite drainage material tightly against the excavated face, lagging or back of wall. Protect the drainage material against physical damage and grout leakage when concrete is to be placed against geocomposite drainage material.
3.Retaining Wall Construction. Construct mechanically stabilized earth walls consisting of a facing system to which steel or polymeric soil reinfor cement is connected. Provide facing of precast concrete panels, cast -in-place concrete or welded wire fabric. Install polymeric soil reinforcement under Section 634. When constructing cast -in-place concrete facing, embed soil reinforcement which extends beyond the temporary facing into the facing concrete. 243 ALASKA 2020 Form welded wire facing by bending the horizontal soil reinforcement 90 degrees upward to form the wire face. Connect the vertical portion of the welded fabric forming the face to the next upper level of soil reinforcement. Place a separate backing mat and hardware cloth immediately behind the vertical portion of soil reinforcement. Provide a precast reinforced or cast -in-place concrete leveling pad at each panel foundation level. Place panels or wire fabr ic and support to achieve the final position. Place and compact structure backfill material at the same time as placement of facing and soil reinforcement, without distortion, damage, or displacement of the facing or soil reinforcement. Backfill to an elev ation approximately 1- 1/4 inch above the facing connection level before placing the next level of soil reinforcement. Roughly level the backfill material before placing the soil reinforcement. Uniformly tension all soil reinforcement to remove any slack in the connection or material. Install joint filler, bearing pads, and joint -covering material concurrently with face panel placement. Furnish and install instrumentation for monitoring corrosion, where specified.
511-4.01 MEASUREMENT . See Section 109, by t he square foot of wall face. The vertical height
of each section is measured on the outer face from the bottom of the lowermost face element to the top of the wall.
511-5.01 Payment.
Excavation and backfill are paid for under Section 205. Payment will be made under: PAY ITEM Item Number Item Description Unit 511.0001.____ Mechanically Stabilized Earth Wall SF 244 ALASKA 2020 SECTION 512 FORMS AND FALSEWORK
512-1.01 DESCRIPTION . Design, construct, maintain and remove forms and falsework used to
form or temporarily support structural concrete until the structure is self supporting.
512-1.02 Definitions .
COMPRESSIVE STRENGTH . See definitions in Subsection 501- 1.02. FALSEWORK. A temporary structure erected to support the permanent structure, in the process of construc tion, until the permanent structure attains adequate strength to become self -supporting and capable of supporting other imposed loads. FORMS. Also known as formwork, are a temporary structure or mold used to retain the plastic concrete in its designated shape while the concrete is curing and gaining sufficient strength to maintain its designated shape. HAUNCH. A thickened portion of a concrete deck filling the space between the top of the girder and the bottom of the roadway slab. INFORMATIONAL FIELD TEST. See definitions in Section 501- 1.02.
512-2.01 MATERIALS. As specified or approved.
DESIGN AND CONSTRUCTION REQUIREMENTS
512-3.01 Submittals.
1.Falsework Plan . When complete details for falsework are not shown on the Plans, prepare and submit a falsework pla n, prepared and sealed by a Professional Engineer registered in the State of Alaska. When the structure is not open to traffic and is not over or adjacent to railroads or roadways, a falsework plan and independent design check are not required. Include detailed working drawings, material specifications, and supporting calculations to allow for complete review of the falsework plan. For manufactured or proprietary falsework components, include the manufacturer's information, technical bulletins, design data, and other necessary information used in the calculations. Include an independent design check to verify that the design satisfies the Contract requirements. Perform the independent design check by a Professional Engineer registered in the State of Alaska. Independent means the Professional Engineer performing the independent design check is not associated as a subordinate, subsidiary, employee, or member of the business employing the Professional Engineer sealing the falsework design. Submit an independent design check letter, sealed by the Professional Engineer performing the independent design check, certifying the falsework plan meets the Contract requirements of this Section. Include the independent design check letter with the falsework plan submittal .
2.Falsework Inspection Verification . Prior to placing reinforcing steel or other loads, perform a falsework inspection by the Professional Engineer sealing the falsework design. Do not place reinforcing steel until a written verification, signed by the Pr ofessional Engineer sealing the falsework design, stating that the falsework meets the design and construction requirements is provided to the Engineer.
3.Concrete Deck Haunch Dimensions . Prior to placing falsework, submit the girder elevations, required haunch dimensions, and supporting calculations for review. Ensure the haunch dimensions meet the requirements of Subsection 512- 3.05.
Get an email when 511 changes
Alaska revises spec sections through supplementals and new editions. We check this one every week and email you the day it changes. Free, no account.
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 269–271 of 584. View official source ↗