WHAT IS A STABILISED EARTH WALL STRUCTURE?
Composite structures which utilize wall units and
geogrid to create a stable mass that can be designed and constructed
to much greater heights than simple gravity walls. stabilised
earth
wall structures combine the mass of the composite structure with
the strength of the geo-grid to resist external earth pressures.
WHY DO SOME WALLS NEED REINFORCEMENT?
Geo-grid creates a stable mass that allows walls to
be designed and constructed to much greater heights than simple
gravity walls because it stabilizes the soil behind the wall face.
Geo-grid is used to impart tensile strength into soil structures,
allowing such structures to be built taller and steeper than the
soil alone would allow, or for building on soils with bearing capacities
insufficient for supporting a proposed structure. Geo-grid can be
thought of as performing in the soil in much the same way that reinforcing
steel bars perform in the concrete. The amount of geo-grid required
in a retaining wall structure, and the spacing of layers of geo-grid
in the retaining wall structure, must all be determined by the specific
design considerations (wall height, surcharge loadings, soil, etc.)
of the individual project (see
Reinforcement).
HOW HIGH CAN WALLS BE BUILT WITHOUT THE USE OF
GEO-GRID?
The various Keystone retaining wall systems can be
constructed between two-feet and six-feet high (in ideal conditions)
depending on the type of unit, soil conditions, amount of batter
used and surcharge on top of wall. Contact Integrated Brickworks to determine
if your project can be built without the need for geo-grid.
ARE CONCRETE FOOTINGS EVER NECESSARY OR REQUIRED?
In some cases, Keystone walls can be built directly
on six to eight inches of well-compacted granular base. However,
there may be instances to consider the use of a concrete leveling
pad. Examples of this are: applications near water, a taller wall
built on soft subsoils, or a wall that is very long (by using concrete
footing, the contractor can speed up the installation process).
WHAT IS THE BEST MATERIAL ON WHICH TO BUILD THE
WALL?
Angular crushed stone (3/4-inch
aggregate), crushed
gravel or limestone are best for the base pad.
WHAT MATERIALS SHOULD BE USED AS BACKFILL?
A clean, well-draining granular fill, like 3/4-inch aggregate,
is the most effective. Do not use pea gravel, rounded aggregates, excavated surface vegetation or other unsuitable soil types. Other suitable
materials are sand or quarry dust. Use of earth and soils in taller structures
should be verified by an Engineer or qualified persons.
HOW WILL THE DESIGN OF THE WALL AFFECT OR CORRECT
THE DRAINAGE FLOW PATTERNS OF MY SITE?
Since the effects of water and overall drainage flow
patterns represent the most common source of problems for retaining
walls, it is critical that the contractor evaluates the impact that
the property drainage flow patterns will have on the wall, and the
effect that the drainage flow pattern of the newly constructed wall
will, in turn, have on the site.
HOW DO SOIL PROPERTIES AFFECT THE DESIGN OF THE
WALL?
The soil’s shear strength (angle of internal
friction and cohesion and moist soil weight) determines the design
characteristics of the soils for use within the wall structure.
The more granular the soils (the higher the friction angle and drainage
capability) the more efficient the wall design and soils reinforcement
will be. Granular soils can be easily compacted, resulting in a
superior structure performance.
WILL MY LOCAL BUILDING OFFICIAL REQUIRE A DESIGN
PREPARED BY AN ENGINEER?
The Uniform Building Code Section 106.2 requires a
building permit for earth retaining structures over four feet high.
Many local building officials require a design prepared by an engineer.
However, there are many locations that have no provisions for engineered
design.
WHAT DO I NEED TO PREPARE BEFORE I EXCAVATE?
Check with your local utility companies or authorities to
make sure there are no underground pipes or cables running through the
site.
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