HomeMy WebLinkAboutR-421236GENERAL
A. Work shall consist of furnishing and construction of a Keystone Compac Block
Retaining Wall System (or equivalent) in accordance with these specifications and in
reasonably close conformity with the lines, grades, and dimensions shown on the plans.
B. Work includes preparing foundation soil, furnishing and installing leveling pads, drainage
fill, and backfill to the lines and grades shown on the construction drawings.
C. Work includes furnishing and installing geogrid soil reinforcement of the type, size,
location, and lengths designated on the construction drawings.
D. Reference: Barghausen Consulting Engineers, Inc., Detailed Grading Plan & Site Cross
Sections, revised March 2022
SUBMITTALS
A. Contractor shall submit a stamped design with calculations prior to start of work for
approval by the engineer.
B. Contractor shall submit certifications with each delivery or shipment of block and geogrid
QUALITY ASSURANCE
A. Owner shall provide soil testing and quality assurance inspection during earthwork and
wall construction operations. Owner's quality assurance program does not relieve the
contractor of responsibility for wall performance.
DELIVERY, STORAGE AND HANDLING
A. Contractor shall check all materials upon delivery to ensure that the proper type, grade,
color, and certification has been received.
B. Contractor shall protect all materials from damage due to jobsite conditions and in
accordance with manufacturer's recommendations. Damaged materials shall not be
incorporated into the work.
PRODUCTS
DEFINITIONS
A. Modular Unit- a concrete retaining wall element, machine -made from Portland Cement,
water, and aggregates.
B. Structural Geogrid- a structural element formed by a regular network of integrally
connected tensile elements with apertures of sufficient size to allow for interlocking with
surrounding soil, rock, or earth, designed to function primarily as reinforcement.
C. Drainage Fill: drainage aggregate which is placed within and immediately behind
the modular concrete units.
D. Reinforced Backfill: compacted soil which is placed within the reinforced soil volume as
outlined on the plans.
MODULAR CONCRETE RETAINING WALL UNITS
A. Modular Concrete Units shall conform to the following architectural requirements:
Face Color: concrete gray
Face Finish- tri-plane face configuration
Bond Configuration- running with bonds nominally located at midpoint vertically adjacent
units, in both straight and curved alignments.
B. Modular concrete materials shall conform to the requirements of ASTM C1372
(Standard Specifications for Segmental Retaining Wall Units).
C. Modular concrete units shall conform to the following structural and geometric requirements:
Compressive Strength- 4000 psi minimum
Absorption- 8% maximum (6% in northwestern states) for standard weight aggregates
Dimensional Tolerances- ±1/8" from nominal unit dimensions not including rough split
face-, ±1/16" unit height for the top and bottom planes
Unit Size- 100 lb/unit minimum for standard weight aggregates
Inter -unit Shear Strength- 1500 plf minimum at 2 psi normal pressure
Geogrid/Unit Peak Connection Strength: 1000 plf minimum at 2 psi normal force
D. Modular concrete units shall conform to the following constructability requirements -
Alignment and Grid Positioning Mechanism- fiberglass pins, two per unit minimum
Horizontal Spacing between Erected Units: 1/2-inch maximum
SHEAR CONNECTORS
A. Shear connectors shall be 1/2-inch-diameter, thermoset isopthalic polyester,
resin-pultruded, fiberglass reinforcement rods or equivalent to provide connection
between vertically and horizontally adjacent units. Strength of shear connectors
between vertical adjacent units shall be applicable over a design temperature of 10
degrees F to ±100 degrees F.
B. Shear connectors shall be capable of holding the geogrid in the proper design position
during grid pre -tensioning and backfilling.
BASE LEVELING PAD MATERIAL
A. Material shall consist of a compacted crushed rock base or non -reinforced concrete
at the option of the contractor.
DRAINAGE FILL
A. Drainage Fill shall consist of 1-inch "clean" crushed rock meeting the following
gradation tested in accordance with ASTM D422:
Sieve Size Percent Passina
1 inch 100
3/4 inch 75 - 100
No.4 0-10
No. 50 0-5
B. Drainage Fill shall be placed within cores of, between, and behind units a minimum
distance of 12 inches as shown on the plans.
REINFORCED BACKFILL
A. Reinforced Backfill shall be free of debris and generally meet the following gradation
tested in accordance with ASTM D422. Use of backfill that does not conform to this
specification must be approved by the Geotechnical Engineer.
Sieve Size Percent Passina
1 1/4 inch 75 - 100
3/4 inch 75 - 100
No. 40 0 - 60
No. 200 0 - 10
B. The maximum aggregate size shall be limited to 1-1/2 inches, unless field tests have been
performed to evaluate potential strength reductions to the geogrid design due to damage
during construction.
C. Unsuitable soils for backfill (high plasticity clays or organic soils) shall not be used in the
backfill or in the reinforced soil mass.
D. Contractor shall submit reinforced fill sample and laboratory test results to the
Geotechnical Engineer for approval prior to the use of any reinforced fill material.
GEOGRID SOIL REINFORCEMENT
A. Geosynthetic reinforcement shall consist of geogrids manufactured specifically for soil
reinforcement applications and shall be manufactured from high -tenacity polyester yarn
or high -density polyethylene. Polyester geogrid shall be knitted from high -tenacity
polyester filament yarn with a molecular weight exceeding 25,000 meg/m and a carboxyl
end group value less than 30. Polyester geogrid shall be coated with an impregnated
PVC coating that resists peeling, cracking, and stripping.
B. The geogrid manufacturer shall have a manufacturing quality control program that
includes QC testing by an independent laboratory. The QC testing shall include:
-Tensile Strength Testing
-Melt Flow Index (HDPE)
-Molecular Weight (Polyester)
DRAINAGE PIPE
A. If required, the drainage pipe shall be perforated pipe manufactured in accordance
with ASTM D3034.
EXECUTION
EXCAVATION
A. Contractor shall excavate to the lines and grades shown on the construction drawings.
The Geotechnical Engineer shall observe the excavation and provide approval prior to
placement of either leveling material or fill soils. The foundation area shall be proofrolled
as recommended by the Geotechnical Engineer.
BASE LEVELING PAD
A. Leveling Pad material shall be placed to the lines and grades shown on the construction
drawings, to a minimum thickness of 4 inches and extended laterally a minimum of
6 inches in front of, and behind, the modular wall unit.
B. Soil leveling pad material shall be compacted until firm and unyielding, as confirmed by
the Geotechnical Engineer at the time of construction.
C. Leveling Pad shall be prepared to ensure full contact to the base surface of the concrete
units.
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A. First course of units shall be placed on the leveling pad at the appropriate line and
grade. Alignment and level shall be checked in all directions to ensure that all units are
in full contact with the base and properly seated.
B. Place the front units side -by -side. Layout of corners and curves shall be in accordance
with the recommendations of the manufacturer.
C. Install shear connectors to achieve wall batter per approved plans.
D. Maximum stacked vertical height of wall units, prior to unit drainage fill and backfill
placement and compaction, shall not exceed three courses.
E. Place and compact drainage fill behind the wall units concurrently with placement and
compaction of reinforced backfill.
STRUCTURAL GEOGRID INSTALLATION
A. Geogrid shall be oriented with the highest strength axis perpendicular to the wall
alignment.
B. Geogrid reinforcement shall be placed at the strengths, lengths, and elevations shown on
the plans and/or details.
C. The geogrid shall be laid horizontally on compacted backfill and attached to the modular
wall units, after which the next course of modular concrete units shall be placed over the
geogrid. The geogrid shall be pulled taut during backfill placement.
D. Geogrid reinforcements shall be continuous throughout their embedment lengths and
placed side -by -side to provide 100% coverage at each level. Spliced connections
between shorter pieces of geogrid, or gaps between adjacent pieces of geogrid, are not
permitted.
REINFORCED BACKFILL PLACEMENT
A. Reinforced backfill shall be placed, spread, and compacted in such a manner that
minimizes the development of slack in the geogrid and/or damage.
B. Reinforced backfill shall be placed and compacted in lifts not to exceed 12 inches.
Lift thickness shall be decreased, if necessary, to achieve the required density.
C. Reinforced backfill shall be compacted to a minimum of 95% of the maximum dry density
as determined by ASTM D1557. The moisture content of the backfill material prior to and
during compaction shall be at (or slightly above) the optimum moisture content.
D. Only lightweight, hand -operated equipment shall be allowed within 3 feet from the tail of
the modular concrete unit. Consolidation of this zone shall be accomplished with two
passes of a lightweight plate compactor. No density tests shall be taken in this zone.
E. Tracked construction equipment shall not be operated directly upon the geogrid
reinforcement. A minimum fill thickness of 6 inches is required prior to operation of
tracked vehicles over the geogrid. Tracked vehicle turning should be kept to a minimum
to prevent tracks from displacing the fill and damaging the geogrid.
F. Rubber -tired equipment may pass over geogrid reinforcement at speeds less than
5 mph. Sudden braking and sharp turning shall be avoided.
G. At the end of each day of operation, the contractor shall slope the last lift of reinforced
backfill away from the wall units to direct runoff away from the wall face. The contractor
shall not allow surface runoff from adjacent areas to enter the wall construction site.
CAP INSTALLATION
A. Cap units shall be glued to underlying units with polyurenthane adhesive.
AS -BUILT CONSTRUCTION TOLERANCES
A. Vertical Alignment: ±1.5 inches over any 10-foot distance
B. Wall Batter: within 2 degrees of design batter
C. Horizontal Alignment: ±1.5 inches over any 10-foot distance
Corners, Bends, Curves: ±1 foot to theoretical location
D. Horizontal Gap between Erected Units: 1/2-inch maximum
E. Installation Location: with 2 inches of staked base location
FIELD QUALITY CONTROL
A. The wall footings shall be observed by the Geotechnical Engineer on a full-time
basis. Testing of the compacted backfill shall be performed by the owner at least
once every two lifts of backfill placement and compaction.
B. At a minimum, quality assurance should include foundation soil inspection, soil and
backfill testing, verification of design parameters, and observation of construction for
general compliance with design drawings and specifications.
HT
Keystone Compac
Modular Unit (Typ.)
Level Toe Slope
NOTE: Wall Toe Backfill must be placed'
during or immediately after wall construction.
CONSTRUCTION NOTES:
1. Place geogrid on level backfill and
extend over fiberglass pins.
2. Place next Keystone block unit.
3. Pull geogrid taut and place backfill.
4. Stake as required.
GEOGRID & PIN
CONNECTION DETAIL
Not - To - Scale
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NOTE: Geotechnical Engineer shall
evaluate the need for Supplementary
Drainage behind the Reinforcement
Zone during Construction.
TWO-TIER FILL WALL CONDITION
(WALLS 2 & 3)
NOT - TO - SCALE
Not - To - Scale