Specification Guidelines: Allan
Block Retaining Wall Systems
SECTION 1 PART 1: GENERAL
1.1 Scope
Work includes furnishing and installing modular concrete block retaining
wall units to the lines and grades designated on the construction drawings
and as specified herein.
1.2 Applicable Sections of Related Work
Geogrid Wall Reinforcement (see section 2)
1.3 Reference Standards
ASTM C 1372-97 Standard Specifications for Segmental Retaining Wall Units
1.4
Delivery, Storage and Handling
A. Contractor shall check the
materials upon delivery to assure proper material has been received.
B. Contractor shall prevent excessive mud, wet cement and like materials
from coming in contact with the materials.
C. Contractor shall protect the materials from damage. Damaged material
shall not be incorporated in the project.
PART 2: MATERIALS
2.1 Modular Wall Units
A. Wall units shall be ALLAN BLOCK Retaining Wall
units as produced by a licensed Manufacturer.
B. Wall units shall have minimum 28 day compressive strength of 3000
psi (20.7 MP) in accordance with ASTM C-1372-97. The concrete units shall
have
adequate freeze-thaw protection with an average absorption rate of 7.5
lb/ft3 (120 kg/m3) for northern climates and 10 lb/ft3 (160kg/m3) for southern
climates.
C. Exterior dimensions shall be uniform and consistent. Maximum dimensional
deviations shall be .125 inch, (3 mm) not including textured face.
D. Wall units shall provide a minimum of 110 pounds total weight per square
foot of wall face area (1,761 kg/m3). Fill contained within the units may
be considered 80% effective weight.
E. Exterior face shall be textured. Color as specified by owner.
2.2 Wall
Rack
A. Base material shall be well graded compactable aggregate, 0.25
inch to 1.5 inch, (6.4 mm – 38 mm) with no more than 10% passing
the #200 sieve.
B. Drainage material shall be the same as base material.
C. Backfill material shall be site excavated soils when approved by the
engineer unless otherwise specified in the drawings. Unsuitable soils
for backfill (heavy clays or organic soils) shall not be used in the
reinforced
soil mass.
D. Where additional fill is required, contractor shall submit sample
and specifications to the Engineer for approval.
PART 3: WALL CONSTRUCTION
3.1 Excavation
Contractor shall excavate to the lines and grades shown on the construction
drawings. Contractor shall use caution not to over-excavate beyond the
lines shown, or to disturb the base elevations beyond those shown.
3.2 Foundation
Soil Preparation
A. Foundation soil shall be excavated as dimensioned
on the plans and compacted to a min. 90% compaction prior to placement
of the base material.
B. Foundation soil shall be examined by the Engineer to insure 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 material.
3.3 Base
A. Base material shall be placed as shown on construction drawing.
Top of base shall be located to allow bottom wall units to be buried
to proper
depths as per wall heights and specifications.
B. Base material shall be installed on undisturbed native soils or suitable
replacement fills compacted at 90% standard proctor.
C. Base shall be compacted at 90% standard proctor to provide a level
hard surface on which to place the first course of blocks. The base shall
be
constructed to insure proper wall embedment and the final elevation shown
on the plans. Well-graded sand can be used to smooth the top–inch
(12.5 mm) on the level pad.
D. Base material shall be a 3–inch (76 mm) minimum depth for walls
under 4 feet (1.2 m) and a 6 inch (150 mm) minimum depth for walls over
4 feet (1.2 m).
3.4 Unit Installation
A. The first course of wall units shall be placed
on the prepared base with the raised lip facing out and the front edges
tight together. The
units shall be checked for level and alignment as they are placed.
B. Insure that units are in full contact with base. Proper care shall be
taken to develop straight lines and smooth curves on base course as per
wall layout.
C. All cavities in and around the base row shall be filled with base materials
and compacted. Backfill front and back of entire base row to firmly lock
in place. Check again for level and alignment. All excess material shall
be swept from top of units.
D. Install next course of wall units on top of base row. Position blocks
to be offset from seams of blocks below. Perfect "running bond" is
not essential, but a 3-inch (75 mm) minimum offset is recommended. Check
each block for proper alignment and level. Fill all cavities in and around
wall units and to a 12 inch (305 mm) depth behind block with drainage
material. Spread backfill in uniform lifts not exceeding 8 inches (200
mm). Employ methods using lightweight compaction equipment that will
not disrupt the stability or batter of the wall. Hand-operated plate
compaction
equipment shall be used on the block and within 3 feet (.9 m) of wall
to achieve consolidation. Compact to 90% S.P. in backfill beyond consolidation
zone.
E. Install each subsequent course in like manner. Repeat procedure to
the extent of wall height.
F. Allowable construction tolerance at the wall face is 2 degrees vertically
and 1 inch (25 mm) in 10 feet (3 m) horizontally. Specification Guidelines:
Geogrid Reinforcement Systems
SECTION 2 PART 1: GENERAL
1.1 Scope
Work includes furnishings and installing geogrid reinforcement, wall
fill and backfill to the lines and grades designated on the construction
drawings
and as specified herein.
1.2 Applicable Section of Related Work
Section 1: ALLAN BLOCK Modular Retaining Wall Systems.
1.3 Reference Standards
See specific geogrid manufacturer’s reference standards.
1.4 Delivery,
Storage and Handling
A. Contractor shall check the geogrid upon
delivery to assure that the proper material has been received.
B. Geogrid shall be stored above -20º F (-29º C).
C. Contractor shall prevent excessive mud, wet cement or other foreign
materials from coming in contact with the geogrid material.
PART 2: GRID
MATERIALS
2.1 Definitions
A. Geogrid products shall be of high density polyethylene
or polyester yarns encapsulated in a protective coating specifically
fabricated for
use as a soil reinforcement material.
B. Concrete retaining wall units are as detailed on the drawings and
shall be ALLAN BLOCK Retaining Wall Units.
C. Drainage material is free draining granular material as defined
in section: Modular Concrete Retaining Wall systems as "Drainage
Material."
D. Backfill is the soil used as fill for the reinforced soil mass.
E. Foundation soil is the in-situ soil.
2.2 Products
Geogrid shall be the type as shown on the drawings having the property
requirements as described within the manufacturer’s specifications.
2.3
Acceptable Manufacturers
A manufacturer’s product shall be approved by the Engineer.
PART
3: WALL CONSTRUCTION
3.1 Foundation Soil Preparation
A. Foundation soil shall be excavated
to the lines and grades as shown on the construction drawings, or as
directed by the Engineer.
B. Foundation soil shall be examined by the Engineer to assure that
the actual foundation soil strength meets or exceeds assumed design
strength.
C. Over-excavated areas shall be filled with approved compacted backfill
material.
D. Foundation soil shall be proof rolled prior to fill and geogrid
placement.
3.2
Wall Construction
Wall construction shall be as specified under Section 1, Part 3, Wall
Construction.
3.3 Geogrid Installation
A. Install ALLAN BLOCK wall to designated height
of first geogrid layer, backfill and compact behind wall to depth equal
to designated grid length.
B. Cut geogrid to designed embedment length and place on top of ALLAN
BLOCK to back edge of lip. Extend horizontally on compacted backfill.
C. Place next course of ALLAN BLOCK on top of grid and fill block cores
with drainage fill to lock in place. Remove slack in grid and stake to
maintain tension.
D. Lay geogrid at the proper elevation and orientations shown on the
construction drawings or as directed by the Engineer.
E. Correct orientation (strength direction) of the geogrid shall be verified
by the contractor.
F. Follow manufacturer’s guidelines for overlap requirements.
3.4 Fill Placement and Backfill Placement
A. Backfill material shall
be placed in lifts and compacted as specified under Section 1, Part
3.4, Unit Installation.
B. Backfill shall be placed, spread and compacted in such a manner
that minimizes the development of wrinkles in and/or movement of
the geogrid.
C. Only hand-operated compaction equipment shall be allowed within
3 feet, (.9 m) of the wall face.
D. Tracked construction equipment shall not be operated directly
on the geogrid. A minimum backfill thickness of 6 inches (150 mm)
is required
prior to operation of tracked vehicles over the geogrid. Turning
of tracked
vehicles should be kept to a minimum to prevent tracks from displacing
the fill and damaging the geogrid.
E. Rubber-tired equipment may pass over the geogrid reinforcement
at slow speeds, less than 10 MPH (16 Km/H). Sudden braking and sharp
turning
shall
be avoided.
F. The backfill shall be compacted to achieve 90% standard proctor.
Soil tests of the backfill material shall be submitted to the Engineer
for
review and approval prior to the placement of any backfill. The contractor
is
fully responsible for achieving the specified compaction requirements.
The Engineer may direct the contractor to remove, correct or amend
any soil found not in compliance with these specifications.
SPECIAL
CONSIDERATIONS
A. Geogrid can be interrupted by periodic penetration
of a column, pier or footing structure.
B. ALLAN BLOCK walls will accept vertical and horizontal reinforcing
with rebar and grout.
C. If site conditions will not allow geogrid embedment length,
consider the following alternatives: Masonry Reinforced
Walls
Soil Nailing
Earth Anchors
Rock Bolts
Increased Wall Batter
D. ALLAN BLOCK can be used in a wide variety of water applications.
TECHNICAL
SUPPORT
For engineering and technical assistance on projects that fall beyond
the scope of these guidelines, contact your Authorized
Cambridge Distributor for advice.
