The SRW System is composed
of units whose size and weight makes it possible
to construct walls in the most difficult of
locations. curves and other unique layouts
can be easily accommodated. Segmental retaining
walls have the ability to function equally
well in large-scale applications (highway walls,
bridge abutments, erosion control, parking
area supports, etc.) as well as smaller residential
landscape projects.Unlike
rigid retraining wall structures, which may display
cracks when subjected to movement, the flexible
nature of segmental retaining walls allows the
units to move and adjust relative to one another
without visible signs of distress.Typical designs and specifications for
segmental retaining walls should be prepared
by a designer who has technical knowledge of
soil and structural mechanics. Each SRW unit
manufacturer can provide design information tailored
to that product, which will indicate the wall
heights and design conditions when an SRW should
be designed by a qualified engineer. In addition,
SRW systems should be designed by a qualified
engineer when:
- structures will be surcharged
- Walls will be subjected to live loads
- walls will be founded on poor foundations
- the nature of the design conditions requires
special consideration
For soil-reinforced segmental retaining walls,
geosynthetic reinforcement increases the mass of
the composite SRW structure, and therefore controlled
by external stability calculations. Increasing
the length of the geosynthetic layers increases
the SRW's resistance to overturning, base sliding,
and bearing failures. In some instances, the length
of the uppermost layer(s) is locally extended in
order to provide adequate anchorage (pullout capacity)
for the geosynthetic layers. The strength of the
geosynthetic and the frictional interaction with
the surrounding soil may also affect geosynthetic
length.
A sufficient number and strength of geosynthetic
layers must be used to satisfy horizontal equilibrium
with soil forces behind the wall and to maintain
internal stability. In addition, the tension forces
in the geosynthetic layers must be less than the
design strength of the geosynthetic and within
the allowable connection strength between the geosynthetic
and the SRW unit.
Drainage
is an essential part of a properly designed SRW.
Drainage materials are generally well-graded aggregates.
A properly designed drainage system relieves hydrestatic
pressure in the soil, prevents retained soils from
washing through the face of the wall, provides
a stiff leveling pad to support a column of stacked
facing units, and provides a working surface during
construction. Surface water drainage should be
designed to minimize erosion of the topsoil in
front of the walltoe and to direct surface water
away from the structure.
Segmental retaining
walls are generally installed with a small horizontal
setback between units, creating a wall batter into
the retained soil. The wall batter compensitates
for any slight lateral movement of the SRW face
due to earth pressure, ensuring that the finished
wall does not appear to rotate.
In
conventional (gravity) SRWs, where the stability
of the system depends primarily on the mass and
shear capacity of the SRW units, increasing the
SRW unit width or weight provides greater stability,
larger frictional resistance, and larger resisting
moments. in soil-reinforced SRWs, heavier and wider
units may permit a greater vertical spacing between
layers of geosynthetic.
All SRW units provide a means of transferring lateral
forces from one course to the next. Shear capacity
provides lateral stability for this mortarless
wall system. This is accomplished by shear keys,
leading lips, trailing lips, clips, pins, or compacted
columns of aggrigate in open cores.
The primary
benefit of wall embedment is to ensure the SRW
is not undermined by erosion of the soil in front
of the wall. Increasing the depth of embedment
also provides greater stabiliyt when site conditions
include weak bearing capacity of underlying soils,
steep slopes near the toe of the wall, potential
scour at the toe (particularly in waterfront or
submerged applications), seasonal soil volumn changes,
or seismic loads.
The basic elements
of each segmental retaining wall system are the
foundation soil, leveling pads, segmental retaining
wall units, retained soil, drainage fill, and,
for soil-reinforced SRWs, the soil reinforcement.
The success
of any segmental retaining wall installation depends
on complete and accurate field information, careful
planning and scheduling, the use of specified materials,
proper construction procedures and inspection.
It is good practice to have the retaining wall
location verified by the owner's representative.
Existing and proposed finish grades shown on the
drawings should be verified to ensure the planned
design heights are in agreement with the topographic
information from the project grading plan.
The contractor should coordinate the delivery and
storage of materials at the site to ensure unobstructed
access to the work area and availability of materials.
materials delivered to the site should be accompanied
by the manufacturer's certification that the materials
meet or exceed the specified minimum requirements.
Construction occurs in the following sequence:
- excavation and leveling pad construction
- setting, leveling, and backfilling base course
- placement and backfilling of units in succeeding
courses
- placement, tensioning, and backfilling of
soil reinforcement (when required)
- compaction of backfill to the specified density
- capping and finish grading
As with any structure used to retain soil, careful
attention should be paid to the compaction equipment
and procedures used during construction. When compacting
soil within 3 ft. (0.9 m) of the face of a wall,
compaction tools should be limited to hand operated
equipment, preferably a vibrating plate compactor.
Reinforced soil can be compacted with walk-behind
or self-propelled riding compaction equipment.
Where
form meets function.. A retaining wall should serve
a dual purpose of pleasing the eye and blending
the levels of earth into your outdoor living space.
Ideal Wall Systems makes this project easier by
offering a product that is superior to other interlocking
wall systems. towne Tree & Landscaping, Inc.
carefully chooses stones, pavers, and other elements
to enhance your landscape area.
This retaining wall was installed to create a safe
and attrative play area. This multifunctional wall
is a decorative addition to the play area and also
serves to hold in place the play mulch. |
