8101
RETAINING WALLS
1.
GENERAL
This section relates to the supply and erection of proprietary, fabricated, retaining wall
systems.
1.1
DOCUMENTS
Documents referred to in this section are:
NZBC E1/AS1
Surface water, 3.0 Drainage system materials and construction
AS 2439.1
Perforated Plastics Drainage and Effluent Pipes and Fittings
AS/NZS 1254
PVC Pipes and fittings for Stormwater and Surface Water applications
AS/NZS 4671
Steel reinforcing materials
NZS 3104
Specification for concrete production
NZS 3602
Timber and wood-based products for use in building
NZS 3605
Timber piles and poles for use in buildings
1.2
MANUFACTURER’S DOCUMENTS
Manufacturer’s and supplier’s documents relating to work in this section are:
~
Copies of the above literature are available from ~
Web:
~
Email:
~
Telephone:
~
Facsimile:
~
1.3
QUALIFICATIONS
Carry out retaining wall work using competent, experienced people, familiar with the
materials and techniques specified.
2.
PRODUCTS
2.1
CONCRETE
Prescribed mix to NZS 3104, minimum 17.5 MPa. Maximum aggregate size 10 mm.
Timber retaining walls
2.2
TIMBER ELEMENTS
Radiata pine, to NZS 3602, table 1A, Requirements for wood-based building components
to achieve a 50-year durability performance.
2.3
TIMBER POLES
Radiata pine, selected in accordance with NZS 3605, treated H5 to NZS 3602 table 1A,
Requirements for wood-based building components to achieve a 50-year durability
performance and to NZS 3605 for cross-section, length, straightness and strength
branding. Do not put cut ends into ground. Treat all cut ends or notches with a liberal
brush coat of copper napthenate or equivalent wood preservative before sealing with a
bituminous sealer.
Precast concrete retaining walls
2.4
PRECAST CONCRETE UNITS
Reinforcing steel: grade 300 to AS/NZS 4671. Cover: minimum 40 mm. Concrete
strength: a minimum 28 day strength of 20MPa.
2.5
INTERLOCKING CONCRETE BLOCK WALLS
Precast concrete blocks with connecting pins. Pins: 12 mm diameter. Construction
adhesives as required by the precast concrete unit manufacturer.
2.6
BASE LEVELLING PADS
Well graded compacted crushed stone, or concrete, to the retaining wall manufacturer's
requirements.
© CIL Masterspec Basic Educational 2008
8101 RETAINING WALLS Page 1
General
2.7
FIELD RELIEF DRAINS
Perforated plastic piping with filter fabric over.
2.8
FIXINGS AND BOLTS
Hot dipped galvanized steel.
2.9
FILTER FABRIC
High density polyethylene or polypropylene mesh.
2.10
DRAINAGE MATERIAL
Free draining crushed stone, 7 mm to 20 mm in size.
2.11
BACKFILLING MATERIAL
To NZBC E1/AS1: 3.9.5.
3.
EXECUTION
3.1
STORAGE
Take delivery of retaining wall elements in protected pallets, undamaged and dry. Store
on level hard standings, protect from damage and keep dry until laid.
Timber retaining walls
3.2
ERECT TIMBER CRIB WALLS
Excavate, form base for and erect in accordance with the crib wall manufacturer's
requirements and standard details.
3.3
ERECT DRIVEN TIMBER POLE WALLS
Excavate, drive poles, and erect planks; all in accordance with the pole wall
manufacturer's requirements and standard details. Drive poles small end down. Install
timber rails with staggered joints. All rail joints close butted at poles.
Set-out tolerances
From pole centre line:
Misalignment:
Minimum back slope:
3.4
Maximum 20 mm from centre line
Maximum 25 mm at ground level and/or top
3 degrees back slope from vertical
ERECT DRILLED TIMBER POLE WALLS
Excavate, drill to required depth, and set in concrete in pre-drilled holes, and erect planks;
all in accordance with the pole wall manufacturer's requirements and standard details.
Place poles butt end down. Install timber rails with staggered joints. All rail joints close
butted at poles.
Set-out tolerances
From pole centre line:
Misalignment:
Minimum back slope:
Drill diameter:
Min concrete encasement:
Maximum 60 mm from centre line
Maximum 20 mm at retaining face
3 degrees back slope from vertical
Pole butt end diameter + 100 mm
25 mm over the timber pole
Concrete retaining walls
3.5
ERECT CONCRETE CRIB WALLS
Excavate, form base for and erect in accordance with the crib wall manufacturer's
requirements and standard details.
3.6
ERECT INTERLOCKING CONCRETE BLOCK WALLS
Excavate, form base for and erect in accordance with the block wall manufacturer's
requirements and standard details.
© CIL Masterspec Basic Educational 2008
8101 RETAINING WALLS Page 2
Accessories
3.7
SUBSOIL RELIEF DRAINS
Lay perforated DN 100 PVC pipe (made from DN 100 PVC Stormwater pipe to AS/
NZS 1254 class SN 4) or DN 110 corrugated coil HDPE subsoil drainage pipe to stiffness
requirements of AS 2439.1 class 200 or equivalent, firmly in a granular bed in straight
runs to correct gradients, discharging into a cesspit. Carry a free draining granular bed
up and over the pipes without disturbing them, to a total depth of 300 mm. Cover with
filter fabric, to the pipe manufacturer's requirements. Carry the high end of all lines up to
the surface in capped, solid PVC to provide for flushing out.
3.8
BACKFILLING
Compact backfilling in 150 mm loose layers, using a suitable vibrating roller, until no
further compaction is discernible. Top with 150 mm of clean topsoil.
3.9
TAKE AWAY
Take away from the site plant and material not used.
4.
SELECTIONS
Timber retaining walls
4.1
TIMBER ELEMENTS
Timber:
~
Treatment:
~
4.2
TIMBER POLES
Timber:
~
Treatment:
~
Minimum pole butt diameter:
Pole finish:
~
4.3
TIMBER RAILS
Timber:
Treatment:
Size:
~ mm
~
~
~ mm x ~ mm
Precast concrete retaining walls
4.4
PRECAST CONCRETE UNITS
Brand:
~
Type:
~
4.5
INTERLOCKING CONCRETE BLOCK WALLS
Brand:
~
Type:
~
Colour:
~
General
4.6
FIELD RELIEF DRAINS
Pipe brand/type: ~
Fabric brand/type: ~
4.7
FIXINGS AND BOLTS
Minimum coating thickness:
4.8
FILTER FABRIC
Brand:
Type:
~
~
~
© CIL Masterspec Basic Educational 2008
8101 RETAINING WALLS Page 3