6-185
672.05 Submittals The Contractor shall supply wall design com putations, wall
details, dimensions, quantities, and cross sections necessary t o construct the wall. A sample hand calculation including all equations, parameter values used , units, theory, free-body diagram, comparison to design requirements, etc. shall be provi ded. Spread sheet calculations alone are not acceptable. Forty-five days prior to beginning construction of the wall, f our (4) sets of the wall design computations and Shop Drawings shall be submitted to the Resident for review by the Geotechnical Engineer. Mix design information shall be sub mitted at the same time, including aggregate source, current gradation, aggregate qualit y information and concrete unit weight. The contractor shall also submit backfill material test result s as part of the wall submittal package. Backfill material test results shall includ e grain size distribution curve, moisture-density relationship curve, and pH test results requir ed for reinforced backfill only. If geotechnical design is required, the fully detailed plans s hall be prepared in conformance with Section 105 and shall include, but not be limi ted to the following items:
A.A plan and elevation sheet or sheets for each wall, containing 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 location of the original and fi nal ground line.
B.All details for foundations and leveling pads, including detail s for steps in the leveling pads, as well as allowable and actual maximum bearing pressures shall be provided.
C.Details for the barriers, posts, curbs and facing as required b y the project conditions.
D.Design computations prepared and sealed by a licensed Professio nal Engineer.
E.Prior to the beginning of construction, the contractor shall su pply the Resident with two copies of the design-supplier’s Installation Manual. In ad dition, the Contractor shall have two copies of the Installation Manual on the project site.
672.06 Construction Requirements The Precast Concrete Block Gr avity Wall shall have
the following construction requirements:
A.Excavation. The excavation and use as fill or disposal of a ll excavated material shall meet the requirements of Section 203 -- Excavation and Embankme nt, except as modified herein.
B.Foundation. The area upon whic h the prefabricated block gra vity wall structure is to rest, and within the limits shown on the submitted plans, shall be graded for a width equal to, or exceeding, the le ngth of the blocks. Prior to wal l and leveling pad construction, this foundation material shall be compacted to at least 95 percent of 6-186 maximum laboratory dry densit y (AASHTO T-180 Method C or D). F rozen and unsuitable soil shall be removed and replaced with gravel borro w compacted to 95 percent of AASHTO T-180. A concrete leveling pad shall have a minimum thickness of 4 inc hes and shall be constructed as indicated on the plans. Dimensions may be modif ied per the wall supplier’s recommendations, with written approval of the Geotec hnical Engineer. 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 Geotechnical Engineer. The allowable elevation tolerances from the design elevations are + 0.01 feet and -0.02 feet. Leveling pads which do not meet this requirement shall be repai red or replaced as directed by the Resident at no additional cost to the Departmen t. Placement of wall units may begin after the strength of the concrete leveling pad reaches 1000 psi or is adequate to support the proposed loads. Contractor may begin p lacement of concrete block units after 12 hours at his own risk.
C.Method and Equipment. Prior t o erection of the prefabricate d concrete block wall, the Contractor shall furnish the Resident with detailed informa tion concerning the proposed construction method and equipment to be used. The ere ction procedure shall be in accordance with the manufacturer’s instructions. Any uni ts that are damaged due to handling will be replaced at the Contractor’s expense.
D.Installation of Wall Units. A field representative from the wall 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 project. Horizontal joint fillers shall be installed as needed. The maximum offset in any unit hor izontal joint shall be 1/4 in ch. The prefabricated wall blocks shall be installed to a tolerance of plus or minus 3/4 inch in 10 feet in vertical alignment and horizontal alignment.
E.Backfill Placement. Backfill pl acement shall closely follow the erection of each row of prefabricated wall units. The Contractor shall decrease the lift thickness if necessary to obtain the specified density. The maximum lift th ickness shall be 8 inches loose. Gravel borrow backfill shall be compacted in acc ordance with Section
203.12 except that the minimum required compaction shall be at least 92 percent of
maximum density as determined by AASHTO T-180 Method C or D. B ackfill compaction shall be accomplished without disturbance or displac ement of the wall blocks. Sheepsfoot rollers will not be allowed. Whenever a co mpaction test fails, no additional backfill shall be placed over the area until the lif t is recompacted and a passing test achieved. The moisture content of the backfill material prior to and duri ng compaction shall be uniform throughout each layer. Backfill material shall have a placement moisture content less than or equal to the optimum moisture content. Ba ckfill material with a placement moisture content in excess of the optimum moisture co ntent shall be
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 655–656 of 817.