ITEM 610 CELLULAR RETAINING WALLS
610.01
Description
610.02 Approval
by Director
610.03
Materials
610.04
Manufactured Units
610.05
Excavation
610.06 Backfill
610.07 Wall
Construction
610.08 Method of
Measurement
610.09 Basis of
Payment
610.01 Description. This work consists of
constructing retaining walls composed of a series of cells formed by assembling
precast reinforced concrete or galvanized metal units to form stable walls.
Concrete
cellular walls consist of a series of rectangular or triangular cells formed by
building up tiers of precast reinforced concrete units.
Metal
cellular retaining walls consists of pairs of columns,
one column in the plane of the front of the wall and the other column in the
plane of the rear of the wall. The column pairs are spaced longitudinally
with overlapping S-shaped facing and rear members, and transversely with
overlapping U-shaped members.
610.02 Approval by Director. Submit to
the Director for acceptance, 30 days before the work is to begin, drawings of
the units to be furnished. Only submit information for walls produced by
manufacturers whose type of wall, and design of units comprising same, has been
in successful commercial use for a period of at least 3 years.
610.03 Materials. Furnish manufactured units
conforming to:
A. Concrete Cellular Wall. Use concrete conforming to Item 499, Class QC 1. Use reinforcing steel conforming
to 509.02.
B. Metal Cellular Wall. Provide units made from galvanized metal
sheets. Use base metal conforming to AASHTO M 218. Ensure that both sides of the
sheets are galvanized by the hot-dip process. Provide an average spelter coating of not less than 2 ounces per square foot
(610 g/m2) on each side of the sheet and a spelter
coating of at least 1.8 ounces per square foot (550 g/m2) on any 2
1/4 x 2 1/2-inch (57 x 64 mm) area on each side of double exposed
surfaces. Provide finished sheets that are free from injurious defects,
such as blisters, flux, and uncoated spots.
Use metal sheets with
a minimum thickness of 0.057 inch (1.45 mm), unless otherwise shown on the
plans.
Furnish
three copies of the manufacturer’s “Analysis and Coating Test Certificate”
containing the following information covering each project or order on which
galvanized metal walls are furnished.
A.
Heat or heats used for units.
B.
Analysis of each heat.
C.
Amount of spelter coating for each heat.
D.
Total units of each size and thickness.
E.
Name of Contractor.
F.
Name of County, Interstate, U.S., or State route number, and section.
G.
Project number or state purchase order number.
Send
one copy of the certificate to the Laboratory and two copies to the
Engineer. With each copy of the certificate, include a written statement,
signed by a person having legal authority to bind the manufacturer, that the
information and test results are correct and that the material complies with
all contract requirements.
Furnish
5/8-inch (16 mm) diameter bolts, galvanized according to 711.02 and at least 1 1/4 inches (32 mm)
long, measured from the underside of the bolt head.
A. Concrete Cellular Wall. Cast concrete cellular wall units in
substantial, unyielding steel forms. Properly assemble, clean, and oil the
forms before placing concrete in the forms. During the placing and
setting of the concrete, hold the forms rigidly in place on a smooth and level
platform.
Secure the
reinforcement to ensure that it remains in the required position while placing
concrete.
Vibrate the fresh
concrete to fill all space in the form with concrete, to densify
the concrete, and to surround the reinforcement. Reject units with
segregated areas.
Cure the units by
covering with burlap, that is kept wet at least 7 days
or by applying steam for at least 24 hours.
The Engineer will reject reinforced concrete units for any of the
following reasons:
1. Exposure of the reinforcing.
2. Defects that indicate imperfect
mixing, placing, or curing.
3.
Fractures and cracks.
B. Metal Cellular Wall. Fabricate galvanized metal cellular wall units
so that units of the same nominal size are fully interchangeable. Do not drill, punch, or drift holes to correct manufacturing
defects. Replace all units with improperly punched holes.
If possible, maintain
a minimum forming radius of 1 inch (25 mm). Hot-dip galvanize
all units formed with less than 1-inch (25 mm) radius after forming.
610.05 Excavation. Excavate according to Item 203. Obtain the Engineer’s approval that the
bearing for the foundation of the walls is firm and to the proper elevation
before erecting the wall.
610.06 Backfill. Below the elevation of the
proposed ground line at the face of the wall, fill the cells formed by the units
with soil as defined in 203.02.R.
Above the elevation of the proposed ground line at the face of the wall, fill
the cells with material conforming to 203 Granular
Material Type B, except that the percent passing the No. 200 (75 µm) sieve shall not exceed 5 percent.
Place the
material in layers that compact to a depth not to exceed 6 inches (150
mm). Compact the material to the density established by the Engineer
using approved tampers or compactors. Add water as directed by the
Engineer.
Fill the space
behind the wall according to 503.08,
except as noted below.
Backfill around
the wall and in the interior cells, concurrent with wall erection and as close
to the wall elevation as allowed by the type of construction.
Do not use
rolling equipment directly over a portion of the wall until placing at least 12
inches (0.3 m) of compacted fill.
610.07 Wall Construction. Construct
the wall types as follows:
A. Concrete Cellular Wall. Place sills to the required grade and
alignment, and support the entire sill length on the foundation material.
Do not shim the sill.
Place and interlock
the headers perpendicular to the sills and stretches. Use templates to
ensure that members are placed in the proper position and with the proper face
batter.
Before placing sills,
spread two layers of asphalt impregnated paper on all points of contact between
the sills and the foundation material to ensure a uniform
bedding.
After constructing
two tiers of the wall, check and, if necessary, adjust the alignment, grade,
and batter of the units, and backfill to this height before adding subsequent
units. Complete the remainder of the wall.
B. Metal Cellular Wall. Use templates to ensure that members are placed
in the proper position and with the proper face batter.
After placing the
columns and constructing two tiers of the wall, check and, if necessary, adjust
the alignment, grade, and batter of the units, and backfill to this height
before adding subsequent units. Complete the remainder of the wall.
Carefully handle
members, and remove and replace damaged members.
610.08 Method of Measurement. The
Department will measure Cellular Retaining Wall by the number of square feet
(square meters) of facial area complete in place.
610.09 Basis of Payment. Payment
is full compensation for furnishing all materials, backfilling, including the
interior filling, watering, and disposing of surplus materials.
The
Department will not pay for replacing any unit with improperly punched holes.
The
Department will not pay for removing or replacing members damaged during
handling.
The
Department will pay for Excavation Not Including Embankment Construction under
Item 203.
The
Department will pay for accepted quantities at the contract price as follows:
Item
Unit
Description
610
Square
Foot
Cellular Retaining Wall
(Square Meter)