SECTION 32 32 23
SPECIFICATION FOR STONEBRIDGE RETAINING WALL SYSTEM
PART 1: GENERAL
1.01
Scope
Work includes furnishing all materials, labor, equipment, and supervision to install a Stonebridge
segmental retaining wall system to the lines and grades designated on the construction
drawings and as specified herein.
1.02
Reference Standards
A. Segmental Retaining Wall Units
ASTM C 140 - Sampling and Testing Concrete Masonry Units
ASTM C 1372 – Standard Specification for Dry-Cast Segmental Retaining Wall Units
B. Geosynthetic Reinforcement
ASTM D 4595 – Standard Test Method for Tensile Properties of Geotextiles by the WideWidth Strip Method
ASTM D 5262 – Standard Test Method for Evaluating the Unconfined Tension Creep and
Creep Rupture Behavior of Geosynthetics
ASTM D 5321 – Standard Test Method For Determining the Coefficient of Soil and
Geosynthetic or Geosynthetic and Geosynthetic by Direct Shear Method
ASTM D 5818 - Standard Practice for Exposure and Retrieval of Samples to Evaluate
Installation Damage of Geosynthetics
ASTM D 6637 – Standard Test Method for Determining Tensile Properties of Geogrids by
the Single or Multi-Rip Tensile Method
ASTM D 6706 – Standard Test Method for Measuring Geosynthetic Pullout Resistance in
Soil
ASTM D 6992 – Standard Test Method for Accelerated Tensile Creep and Creep-Rupture
of Geosynthetic Materials Based on Time-Temperature Superposition Using Stepped
Isothermal Method
C. Soils
ASTM D 422 – Standard Test Method for Particle-Size Analysis of Soils
ASTM D 698 – Standard Test Method for Laboratory Compaction Characteristics of Soil
Using Standard Effort
ASTM D 2487 – Standard Practice for Classification of Soils for Engineering Purposes
ASTM D 4318 – Standard Test Method for Liquid Limit, Plastic Limit and Plasticity Index of
Soils
ASTM D 6913 – Standard Test Methods for Patricle-Size Distribution (Gradation) of Soils
Using Seive Analysis
STONEBRIDGE RETAINING WALL SYSTEM
JUNE 2011
ASTM D 6938 – Standard Test Method for In-Place Density and Water Content of Soil and
Soil-Aggregate by Nuclear Methods (Shallow Depth)
ASTM G 51 – Standard Test Method for Measuring pH of Soil for Use in Corrosion Testing
D. Drainage Pipe
ASTM F 405 – Standard Specification for Corrugated Polyethylene (PE) Pipe and Fittings
ASTM F 758– Standard Specification for Smooth-Wall Polyvinyl Chloride (PVC) Plastic
Underdrain Systems for Highway, Airport or Similar Drainage
E. Engineering Design
NCMA Design Manual for Segmental Retaining Walls, Third Edition
ASTM D 6638 – Standard Test Method for Determining the Connection Strength Between
Geosynthetics Reinforcement and Segmental Concrete Units
ASTM D 6916 – Standard Test Method for Determining the Shear Strength Between
Segmental Concrete Units
F. Where specifications and reference documents conflict, the Wall Design Engineer shall make
the final determination of applicable document.
1.03
Submittals
A.
The Contractor shall submit manufacturer's certifications stating that the Stonebridge
units, geosynthetic reinforcement, reinforced backfill, and stone fill meet the requirements of
Part 2.0 of this specification. The certifications shall be provided 30 days prior to the start of the
work.
B.
The Wall Installer shall provide a list of successful projects with references showing that
they are qualified and have a record of successful performance installing segmental block walls.
C.
The Professional Engineer responsible for the wall design shall submit a set of stamped
construction drawings and design calculations for the Stonebridge retaining wall system. The
Professional Engineer must be experienced in segmental retaining wall design and registered in
the State where the wall is to be built. The design shall clearly state the material properties,
design methodology, and factors of safety or load and resistance factors used. The design shall
consider wall stability, including bearing capacity, global or slope stability, and settlement. The
design shall address both internal and external drainage of the wall.
1.04
Delivery, Storage, and Handling
A.
The Contractor shall inspect the materials upon delivery to assure that proper type and
grade of material and color of Stonebridge units has been received.
B.
The Contractor shall store and handle materials in accordance with manufacturer's
recommendations and in a manner to prevent deterioration or damage due to moisture,
temperature changes, contaminants, corrosion, breaking, chipping or other causes.
C.
The Contractor shall prevent excessive mud, wet cement and like materials from coming
in contact with the Stonebridge units.
D.
The Contractor shall protect geosynthetic material from direct sunlight or UV exposure.
Any protective covering on geosynthetic material shall remain until immediately before
installation.
E.
The Contractor shall protect the materials from damage. Damaged material shall not be
incorporated into the Stonebridge retaining wall.
SECTION 323223 - 2
STONEBRIDGE RETAINING WALL SYSTEM
JUNE 2011
PART 2: MATERIALS
2.01
Wall Units
A.
Wall units shall be Stonebridge as produced by a licensed manufacturer.
B.
Wall units shall meet the requirements of ASTM C1372, except that the minimum required
net average compressive strength shall be 4000 psi (27.6 MPa).
C.
Exterior block dimensions shall be uniform and consistent. Maximum dimensional
deviations shall be 1/8 inch (3 mm) excluding the architectural surface.
2.02
Geosynthetic Reinforcements
Geosynthetic reinforcement shall consist of high-tenacity PET geogrids or geotextiles
manufactured for soil reinforcement applications. The type, strength and placement of the
geosynthetic reinforcement shall be as specified by Wall Design Engineer in the construction
drawings and specifications. Only geosynthetic reinforcements which have been tested with
Stonebridge units according to ASTM D6638 and ASTM D 6916 shall be considered for use.
2.03
Drainage Pipe
A.
The drainage collection pipe shall be a perforated or slotted PVC or corrugated HDPE
pipe. The pipe may be wrapped with a geotextile that will function as a filter.
B.
Drainage pipe shall be manufactured in accordance with ASTM F 405 or ASTM F 758.
2.04
Leveling Pad
Leveling Pad material shall consist of a compacted, open-graded or dense-graded crushed
stone or non-reinforced concrete as shown on the construction drawings.
2.05
Stone Fill
A.
Stone fill shall be angular, clean stone meeting the gradation requirements of ASTM No.
57 Stone, as defined in ASTM C33 and determined in accordance with ASTM D422:
Sieve Size
Percent Passing
1 ½ inch
1 inch
½ inch
No. 4
No. 8
100
95-100
25-60
0-10
0-5
B.
Stone fill shall be used in the cores, between, and at least 12 inches (300 mm) behind
Stonebridge units.
2.06
Reinforced Backfill
A.
Material used as backfill in the reinforced soil zone shall meet the requirements detailed
in the construction drawings and specifications prepared by the Professional Engineer
responsible for the wall design.
B.
The Plasticity Index of the backfill material shall be less than 6. Organic soils and frost
susceptible soils shall not be used.
C.
The pH of the backfill material shall be between 3 and 9 when tested in accordance with
ASTM G 51.
D.
The Contractor shall submit a sample of any imported backfill to the Owner’s
Geotechnical Engineer for pre-approval.
SECTION 323223 - 3
STONEBRIDGE RETAINING WALL SYSTEM
2.07
JUNE 2011
Geotextile Filter Fabric
Geotextile filter fabric shall nonwoven, needle-punched, polypropylene material with a
minimum normal weight of 4 oz/sq. yd.
PART 3: CONSTRUCTION OF WALL SYSTEM
3.01
Construction Observation
A.
The Owner or Owner's Engineer should verify the materials supplied by the Contractor
meet all the requirements of the specification. This includes all submittals and proper installation
of the system.
B.
The Contractor's field construction supervisor shall have demonstrated experience and
be qualified to direct all work at the site.
3.02
Excavation
A.
The Contractor shall verify location of existing structures and utilities prior to excavation,
and shall take appropriate measures to insure they are adequately protected before starting
any wall excavation.
B.
The Contractor shall excavate to the lines and grades shown on the construction
documents. The Contractor shall take precautions to minimize over-excavation. Excavation
support, if required, shall be designed by the Contractor.
3.03
Foundation Soil Preparation
A.
Native foundation soil shall be compacted to 95% of Standard Proctor as determined by
ASTM D-698 prior to placement of the Leveling Pad material.
B.
In-situ foundation soil shall be examined by the Owner’s Geotechnical Engineer to ensure
that the actual foundation soil strength meets or exceeds assumed design strength. Soil not
meeting the required strength shall be removed and replaced with acceptable, compacted
material.
C.
Over-excavation and replacement of unsuitable foundation soils shall be at the direction
of the Owner’s Geotechnical Engineer. Any additional compensation for over-excavation,
which falls outside of the contract limits, must be pre-approved in a written change order signed
by the Contractor, Engineer, and Owner or Owner’s Representative.
3.04
Leveling Pad Preparation
A.
Leveling pad shall be placed as shown on the construction drawings. The leveling pad
shall be constructed to the proper elevation shown on the plans. The leveling pad shall have
minimum depth of at least 6 inches (150 mm), and should extend laterally at least 6 inches (150
mm) in front and 12 inches (300 mm) behind the bottom Stonebridge unit.
B.
If the construction drawings require a crushed stone leveling pad, the stone shall be
placed in uniform loose lifts a maximum of 6 inches (150 mm) thick and consolidated with a
minimum of three passes with a 24 inch (600 mm) wide, walk-behind, vibrating plate compactor.
The compactor shall be capable of delivering a minimum of 2000 lb (9 kN) centrifugal force.
C.
If the construction drawings require a concrete leveling pad, the pad shall be allowed to
cure to the minimum strength specified in the construction documents prior to placement of the
bottom course of Stonebridge units.
D.
Leveling pad shall provide a firm, smooth, and level surface on which to place the
Stonebridge units. There shall be full contact of the Stonebridge units on the leveling pad.
SECTION 323223 - 4
STONEBRIDGE RETAINING WALL SYSTEM
3.05
JUNE 2011
Stonebridge Unit Placement
A.
Properly mark the location of the retaining wall. Use a string line or offset stakes to
establish horizontal and vertical alignment.
B.
For the bottom course of Stonebridge units, remove the bottom lip from the back edge
of the blocks with a hammer and chisel so the blocks will lie flat on the leveling pad.
C.
Place a complete row of blocks on the prepared leveling pad. Blocks should be placed
tight together. Check all blocks for level from front to back and side to side as they are placed.
D.
Place and compact stone fill in the cores of the units, between the units, and at least 12”
(300 mm) behind the wall.
E.
Place reinforced or retained soil between the stone and the back of the excavation.
F.
Following backfill, re-check all units for level and alignment and sweep the top of each
course of blocks clean before starting construction of the next course.
G.
Place the next course of Stonebridge units on top of the previous course. Stonebridge
units should be placed to establish a running bond, where the block straddles and is centered
on the two blocks below it. Cut blocks as needed to maintain a running bond. Partial units shall
be at least 6" (150 mm) long and shall not be placed directly on top of each other. Partial units
shall be adhered in place with a concrete adhesive specifically formulated for segmental
concrete block wall construction.
H.
Push the Stonebridge blocks forward until the lip on the back of the block comes in full
contact with the blocks below.
I.
Broken, chipped, stained or otherwise damaged units shall not be placed in the wall.
3.06
Geosynthetic Reinforcement Placement
A.
All materials shall be installed at the proper elevation and orientation as shown in the wall
details on the construction drawings. The geosynthetic reinforcement shall be installed in
general accordance with the manufacturer's recommendations.
B.
Install geosynthetic material with the strong direction (roll direction) into the reinforced
soil zone. The geosynthetic must be placed in a continuous sheet throughout its length from the
connection at the Stonebridge units to the back of the reinforced zone. Overlap or splice
connections of the geosynthetic material are not permitted. Adjacent sections of geosynthetic
material shall be placed in a manner to assure that the horizontal coverage shown on the plans
is provided.
C.
Place geosynthetic material on top of a course of Stonebridge units at the elevations
shown on the construction drawings. Secure the front end of the geosynthetic material with the
next course of blocks. Make sure the geosynthetic material is as close as possible to the front
face of the wall without being visible. Pull the geosynthetic material taut to eliminate any folds.
Use pins, staples, or other methods recommended by the manufacturer to maintain tension on
the geosynthetic while placing the reinforced fill.
3.07
Backfill Placement
A.
The reinforced backfill shall be placed as shown in construction plans. The maximum
loose lift thickness shall not exceed 8 inches (200 mm). Wet or dry the backfill material as
needed to place the material within 2% of the optimum moisture content. Compact the backfill
material to a minimum 95% of Standard Proctor as determined by ASTM D-698. Backfill shall be
placed, spread and compacted in such a manner that minimizes the development of wrinkles
or movement of the geosynthetic reinforcement and the wall facing units.
SECTION 323223 - 5
STONEBRIDGE RETAINING WALL SYSTEM
JUNE 2011
B.
Only hand-operated compaction equipment shall be allowed within 3 feet (1 meter) of
the front of the wall face. All compaction equipment should be large enough to achieve
desired compaction, but not so large as to move the wall blocks. Monitor the wall blocks for
movement during compaction and reset them if required prior to proceeding.
C.
Construction equipment shall not be operated directly on the geosynthetic
reinforcement. A minimum backfill thickness of 6 inches (150 mm) is required prior to operation of
tracked vehicles over the geosynthetic reinforcement. Turning of tracked vehicles should be
kept to a minimum to prevent displacing the fill and damaging or moving the geosynthetic
reinforcement.
D.
Place retained soil immediately between the reinforced soil zone and the back of the
excavation. Material should be placed in loose lifts of 8 inches (200 mm) maximum and
compacted to 95% of Standard Proctor as determined by ASTM D-698. Bring the reinforced and
retained soil up to grade at the same time. At no time should the elevation of the reinforced soil
be more than 1 Stonebridge unit higher than the retained soil.
E.
At the end of each day's operation, the wall contractor shall slope the last level of
backfill away from the wall facing to direct runoff of rainwater away from the wall face. The
general contractor is responsible for ensuring surface runoff from adjacent areas is not allowed
to enter the wall construction area.
3.08
Stone fill and Drain Placement
A.
Stone fill shall be placed to the minimum finished thickness and widths shown on the
construction drawings.
B.
Place the stone in uniform loose lifts a maximum of 8 inches (200 mm) thick. Consolidate
the stone with a minimum of three passes with a 24 inch (600 mm) wide, walk-behind, vibrating
plate compactor capable of delivering a minimum of 2000 lb (9 kN) centrifugal force.
C.
Drainage collection pipes shall be installed to maintain gravity flow of water outside of
the reinforced soil zone. The pipe should daylight at the ends and/or through the face of the
wall to allow for drainage. Connection to a catch basin or active storm sewer should only be
made under the direction of the Professional Engineer responsible for the wall design.
D.
All drain pipes shall be placed as shown in the construction drawings.
E.
Secondary collection drain pipes should be sloped a minimum of two percent to provide
gravity flow into the main collection drain pipe. Drainage laterals shall be spaced at a maximum
of 50 feet (15 meters) along the wall face.
3.09
Cap Block Placement
The cap block and/or top Stonebridge unit shall be bonded to the Stonebridge units below
using concrete adhesive specifically formulated for segmental block wall construction. The
block shall be dry and swept clean prior to adhesive placement.
3.10
Construction Tolerances
A.
Vertical alignment shall be within ± 1.25 inches (32 mm) over any 10 feet (3 m).
B.
Horizontal alignment shall be within ± 1.25 inches (32 mm) over any 10 feet (3 m).
C.
Rotation alignment shall be within ± 2 degrees of design batter.
PART 4: MEASUREMENT AND PAYMENT
4.01
Measurement
SECTION 323223 - 6
STONEBRIDGE RETAINING WALL SYSTEM
JUNE 2011
The unit of measurement for furnishing the Stonebridge retaining wall system shall be the vertical
square foot of wall surface from the top of the leveling pad to the top of the wall, including
coping. The quantity to be paid shall include all costs to supply and install the Stonebridge
retaining wall system as shown in the construction drawings and specificaitons. Excavation of
unsuitable materials and replacement with select fill must be pre-approved in a written change
order and shall be paid for under separate pay item(s).
4.02
Payment
A.
Payment shall be made under:
Pay Item
Pay Unit
Stonebridge Reinforced SRW
Sq. Ft (Square Meter)
PART 5: AVAILABILITY
Rosetta Hardscapes, LLC
05481 South US-31,
Charlevoix, MI 49720
1-877-777-6558
www.discoverrosetta.com
Updated 06/06/11
SECTION 323223 - 7