6-203 submitted to the Resident for review by the Department. The fu lly detailed plans shall be prepared in conformance with Subsection 105.7 of the Standard S pecifications and shall include, but not be limited to the following items:
A.A plan and elevation sheet or sheets for each wall, contain ing the following: elevations at the top of leveling pads, the distance along the face of the wall to all steps in the leveling pads, the designa tion as to the type of prefabr icated module, the distance along the face of the wall to whe re changes in length of the un its occur, the location of the original and final ground line. B. All details, including reinforcing bar bending details, sha ll be provided. Bar bending details shall be in accordance with Department standard s.
C.All details for foundations and leveling pads, including de tails for steps in the leveling pads shall be provided. The maximum calculated factor ed bearing pressure under the Prefabricated Concrete Modular Gravity wall shall be indicated on the wall plans. D. All prefabricated modules shall be detailed. The details s hall show all dimensions necessary to construct the element, and all reinforc ing steel in the element.
E.The wall plans shall be prepared and stamped by a Professio nal Engineer.
F.Four weeks prior to the beginning of construction, the cont ractor shall supply the Resident with two copies of the design-supplier’s Installation Manual. In addition, the Contractor shall have two copi es of the Installation Manual on the project site.
674.05 Construction Requirements Excavation The excavation and use as fill or disposal of all excavated material shall
meet the requirements of Section 203 -- Excavation and Embankme nt, except as modified herein. Foundation The area upon which the modular gravity wall struc ture is to rest, and within the limits shown on the submitted plans, shall be graded for a width equal to, or exceeding, the length of the module. Prior to wall and levelin g pad construction, this foundation material shall be compacted to at least 95 percent o f maximum laboratory dry density, determined using AASHTO T180, Method C or D. Frozen s oils and soils unsuitable or incapable of sustaining the required compaction, shall be removed and replaced. A concrete leveling pad shall Leveling pad shall have a minimu m thickness of 4 inches and shall be constructed as indicated on the plans. The leveling pad shall be cast to the design elevations as shown on the plans, or as required by the wall supplier upon written approval of the Resident. Allowable elevation tolerances are + 0.01 ft and -0.02 ft from the design elevations. Leveling pads which do not meet this requir ement shall be repaired or 6-204 replaced as directed by the Resident at no additional cost to t he Department. Placement of wall units may begin after 24 hours curing time of the concrete leveling pad. Method and Equipment Prior to er ection of the Prefabricated C oncrete Modular Gravity Wall, the Contractor shall furnish the Resident with de tailed information concerning the proposed construction method and equipment to be used. The erection procedure shall be in accordance with the manufacturer’s instructions. Any pre -cast units that are damaged due to handling will be replaced at the Contractor’s expense. Installation of Wall Units A field representative from the wa ll system being used shall be available, as needed, during the erection of the wall. The services of the representative shall be at no additional cost to the Department . Vertical and horizontal joint fillers shall be installed as shown on the plans. The maximum offset in any unit joint shall be 3/4 in. The ove rall vertical tolerance of the wall, plumb from top to bottom, shall not exceed 1/2 in per 10 ft of wall height. The prefabricated wall units shall be installed to a tolerance of p lus or minus ¾-in in 10 ft in vertical alignment and horizontal alignment. Select Backfill Placement Backfill placement in the interior of the wall units and behind the wall shall progress simultaneously following the ere ction of each row of prefabricated wall units. The maximum lift thickness shall be 8 in., loose measure, and be thoroughly compacted by mechanical or vibratory compactors. The Contractor shall decrease the lift thickness if necessary to obtain the specifie d density. Gravel borrow backfill shall be compacted in accordance with Subsection 203.1 2 except that the minimum required compaction shall be 92 percent of maximum density as d etermined by AASHTO T180 Method C or D. Backfill compaction shall be accomplished without disturbance or displacement of the wall units. Sheepsfoot rollers will not be allowed. Puddling for compaction will not be allowed. Whenever a compaction test fai ls, no additional backfill shall be placed over the area until the lift is recompacted and a passing test achieved. The moisture content of the backfill material prior to and dur ing compaction shall be uniform throughout each layer. Backfill material shall have a placement moisture content less than or equal to the optimum moisture content. Backfill m aterial with a placement moisture content in excess of the optimum moisture content shal l be removed and reworked until the moisture content is uniform and acceptable throughout the entire lift. The optimum moisture content shall be determined in accordance with AASHTO T180, Method C or D. At the end of the day’s operations, the Contractor shall shape the last level of backfill so as to direct runoff of rain water away from the wall face.
674.06 Method of Measurement Prefabricated Concrete Modular G ravity Wall will
be measured by the square foot of front surface not to exceed t he dimensions shown on the contract plans or authorize d by the Resident. Vertical and hor izontal dimensions will be from the edges of the facing units. No field measurements for computations will be made unless the Resident specifies, in writing, a change in the limi ts indicated on the plans. 6-205
674.07 Basis of Payment The accepted quantity of Prefabricate d Concrete Modular
Gravity Retaining Wall will be paid for at the contract unit pr ice per square foot complete in place. Payment shall be full compensation for furnishing all l abor, equipment, materials, professional services, and incidentals necessary for designing, fabricating, furnishing and installing the prefabricated concrete modular gravity wall and accessories. Cast-in-place concrete leveling pad, pre-cast concrete units, backfill, beddi ng material, hardware, joint fillers, woven drainage geotextile, cast-in-place coping, traff ic barrier, and technical field representative will not be measured and paid for separately, bu t will be incidental to the square foot pay item. There will be no allowance for excavating and backfilling for the Prefabricated Concrete Modular Gravity Wall beyond the limits shown on the ap proved submitted plans, except for excavation required to remove unsuitable subsoil in preparation for the foundation, Payment for excavating unsuitable material shall b e full compensation for all costs of pumping, drainage, sheeting, bracing and incidentals f or proper execution of the work, and will be paid as common excavation in accordance with Section 203. Payment will be made under: Pay Item P a y U n i t
674.10 Prefabricated Concrete Modular Gravity Wall Square Fo ot
SECTION 675 – SOIL NAIL WALL Reserved SECTION 676 - SOLDIER PILE AND LAGGING WALL Reserved SECTION 677 - MECHANICALLY STABILIZED EARTH RETAINING WALL
677.01 Description The work under this item shall consist of design, fabrication,
furnishing, transportation, and erection of Mechanically Stabil ized Earth (MSE) retaining wall system of the required type, including miscellaneous items necessary for a complete installation. The MSE retaining walls shall consist of reinforcing strips or reinforcing mesh earth wall systems utilizing architectural precast concrete facing pa nels supported on cast-in-place concrete leveling pads. All reinforcing strips or mesh materia l shall consist of galvanized steel. The wall structures shall be dimensioned to achieve the design criteria shown on the plans and specified herein. The MSE retaining walls shall be constructed in accordance wit h these specifications and in conformity with the lines, grades, design criteria, and dimensions shown on the plans or established by the Geotechnical Engineer.
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 673–675 of 817.