2-120 SECTION 225 – CONCRETE RETAINING WALL
225.01 DESCRIPTION . This work shall consist of designing, detailing, fabricating, furnishing, and
erecting a precast or cast -in-place concrete retaining wall at the locations specified and in conformance with the lines and grades shown on the Plans or as directed by the Eng ineer.
225.02 MATERIALS . Materials shall meet the requirements of the following subsections:
Granular Backfill for Structures ................................ ................................ ................. 704.08 Drainage Aggregate ................................ ................................ ................................ ...704.16 Bar Reinforcement ................................ ................................ ................................ .....713.01 Mechanical Splices for Bar Reinforcement ................................ ............................... 713.02 Welded Wire Reinforcement ................................ ................................ ..................... 713.0 3 Precast Concrete Retaining Wall Systems ................................ ................................ .760.0 5 Concrete shall meet the requirements of Section 501 for Performance -Based Concrete, Class PCS, unless otherwise specified in the Contract. Reinforcing steel shall meet the requirements for Level I I corrosion resistance unless otherwise specified in the Plans.
225.03 DESIGN REQUIREMENTS . The wall shall be designed and constructed in accordance with the
AASHTO LRFD Bridge Design Specifications , the Plans, the design criteria, and the geotec hnical information specified in the Contract. Precast and cast -in-place concrete retaining walls shall employ concrete facing. All wall components shall have a minimum design life of 100 years.
225.04 GENERAL REQUIREMENTS . Unless noted otherwise herein, cast-in-place concrete retaining
walls shall meet the requirements of Section 501 and Section 507 as applicable. Precast concrete retaining walls shall meet the requirements of Section 540 and Section 649 as applicable. When the pay item Retaining Wall , Concrete is included in the Contract, the Contractor may choose to use either a precast or cast -in-place concrete retaining wall at their discretion. The wall shall meet the requirements for the applicable type as noted above. 2-121 225.05 SUBMITTALS . Working drawings shall be submitted in accordance with Subsection 105 .06. Submittals for precast concrete shall also meet the requirements of Subsection 540.04 . The submittal shall include, but not be limited to, all of the following that apply to the particular wall system or type being constructed:
a.Complete design drawings and design calculations substantiating that the proposed design satisfies the design parameters in the Contract. The wall design drawings and design calculations shall be signed , stamped, and dated by a professional engineer.
b.A plan view of the wall showing the details within the limit of the retaining wall system and the centerline of any drainage pipe which is behind or passes under or through the wall.
c.An elevation view of the wall which shall include the elevations at the top of the wall, at all horizontal and vertical break points and at least every 50 feet along the face of the wall, and at all steps in the leveling pads. The elevation view shall also in clude the designation as to the type of panel or block, the length of soil reinforcing elements, the distance along the face of the wall to where changes in length of the soil reinforcing elements occur, and an indication of the final ground line.
d.A typical cross section or cross sections showing the existing ground conditions and proposed grades.
e.All details for foundations and leveling pads, including details for steps in the footings or leveling pads, as well as design maximum and minimum bearing pressures.
f.All details for the wall system including all dimensions necessary to construct the wall.
g.Details of the drainage systems or other facilities required to accommodate the system.
h.The details for connection between the wall and the so il reinforcements.
i.The details for diverting soil reinforcements around obstructions such as guard rail posts, piles, catch basins, and utilities.
j.All reinforcing details, including type, strength, locations, and lengths of reinforcement used.
k.Any general notes required for the construction of the wall. 2-122 (l) A listing of the summary of quantities for each wall.
m.Working drawings shall demonstrate compatibility in how the retaining wall will adjoin adjacent structures designed by others.
n.Working drawings shall include call -outs indicating the applicable AASHTO or ASTM material grades.
225.06 Inspection .
a.Cast-In-Place Concrete . Cast -in-place concrete will be inspected in accordance with Section 501 .
b.Precast Concrete . Precast concrete will be inspected in accordance with Section 540 .
c.Concrete Finish . No surface voids or bug holes greater than 5/8 inch in diameter and more than 1/4 inch deep will be allowed in the finished exposed surface. Surface voids or bug holes th at are less than described shall not exceed 1% of the finished exposed surface with no 6 inch by 6 inch area containing more than 3 surface voids or bug holes. The concrete surface for the front face shall meet the requirements noted in the Plans. Any repa irs to the front face shall match the color and finish of the surface and be approved by the Engineer.
225.07 CONSTRUCTION REQUIREMENTS . Foundation soil, leveling pad, and backfill material shall
be compacted to not less than 95% of the material’s maximum dry density as determined by AASHTO T 99, Method C . Field density quality control shall be conducted by the Contractor in accordance with AASHTO T 310 at a frequency of no less than once per 500 cubic yards.
225.08 METHOD OF MEASUREMENT . The quantity of Retaining Wall, Cast-In-Place Concrete ;
Retaining Wall , Precast Concrete ; and Retaining Wall , Concrete to be measured for payment will be on a lump sum basis in the complete and accepted work .
225.09 BASIS OF PAYMENT . The accepted quantity of Retaining Wall, Cast -In-Place Concrete;
Retaining Wall, Precast Concrete; and Retaining Wall, Concrete will be paid for at the Contract lump sum price . Payment will be full compensation for designing, deta iling, fabricating, transporting, handling, erecting, and installing the materials specified, including but not limited to the tieback system, geotextile fabric, backfill material, concrete, bar reinforcement and welded steel wire fabric, drainage pipe, dr ainage aggregate, precast concrete facing panels, precast concrete blocks, soil reinforcements, attachment devices, fasteners, bearing blocks, shims, geomembrane, and expansion material; any excavation, sheeting, bracing, dewatering, and siltation control; preparing and submitting working drawings; and for furnishing all labor, tools, equipment, and incidentals necessary to complete the work. 2-123 Any grouting work, such as fairing out unevenness between adjacent concrete pieces and filling leveling screw hole s, shear keys, transverse anchor recesses, and dowel holes, will be considered incidental to the Contract lump sum price for the applicable Section 225 pay item. Payment will be made under: Pay Item Pay Unit 225.0300 Retaining Wall , Cast -In-Place Concrete ................................ ................... Lump Sum 225.0400 Retaining Wall , Precast Concrete ................................ ............................. Lump Sum 225.0500 Retaining Wall , Concrete ................................ ................................ .......... Lump Sum 2-124 SECTION 227 – MECHANICALLY STABILIZED EARTH RETAINING WALL
227.01 DESCRIPTION . This work shall consist of designing, detailing, fabricating, furnishing, and
erecting mechanically stabilized earth (MSE) retaining walls constructed in accordance with these specifications and in conformance with the lines, grades, d etails, and dimensions shown on the Plans or as directed by the Engineer. Construction of the MSE retaining wall system shall consist of placement and compaction of select granular backfill, a non -structural leveling pad, precast concrete face panels, an d membrane and soil reinforcement elements mechanically connected to each facing panel.
227.02 MATERIALS . Materials shall meet the requirements of the following subsections:
Drainage Aggregate ................................ ................................ ................................ ...704.16 Select Backfill for MSE Structures ................................ ................................ ............ 704.18 Polyvinyl Ch loride (PVC) Plastic Pipe ................................ ................................ ......710.0 5 Bar Reinforcement ................................ ................................ ................................ .....713.01 Mechanical Splices for Bar Reinforcement ................................ ............................... 713.02 Geotextile for Roadbed Separator ................................ ................................ .............. 720.02 Mechanically Stabilized Earth (MSE) Wall Systems ................................ ................ 760.0 6 Geomembrane Liner ................................ ................................ ................................ ..760.07 Precast concrete shall meet t he requirements of Section 540 . Reinforcing steel shall meet the requirements for Level II corrosion resistance unless otherwise specified in the Plans.
227.03 DESIGN REQUIREMENTS . The MSE retaining wall system shall be designed and constructed
in accordance with the AASHTO LRFD Bridge Design Specifications, the Plans, the design criteria, and the geotechnical information specified in the Contract. The system shall be designed for a design life of 100 years, and any wall reinforcing located above the geomembrane shall have a design li fe of 125 years, both using the corrosion rates given in the AASHTO LRFD Bridge Design Specifications for non -aggressive soil.
Source: Vermont Standard Specifications for Construction, 2024 Edition. Pages 260–263 of 1,380.