LANDSCAPING
GARDEN MAINTENAINCE
POOL SERVICES

Articles of Interest

Retaining Walls


Retaining walls are structures built to increase the stability of a slope.
SLOPE STABILIZATION
Fill areas:

three forces act on filled areas
1          Activating force               - in the form of soil weight
2          Resisting force               - cohesion of existing soil and fill
3          Lateral force                   - horizontal movement

Increase stability of slope
Reduce gradient of slope
Plant regeneration Terracing Retaining walls Improve drainage
Slope reinforcement - pinning, Geo-textile, netting
Control surface water

FUNCTIONS OF RETAINING WALLS

define boundary             - security, privacy
stabilize slopes               - land degradation, erosion support structures          - buildings,
table and chairs containment                   - soil, water etc
separation                      - different areas, level changes increase usable land
aesthetics

Design considerations for retaining walls
Site factors                     - soil type, climate, slope stability, vegetation proximity,
access, drainage
Appearance                   - compatibility with surrounds; function of wall, workmanship, skill,
material availability, maintenance
Costs                             - available funds, material expensive, skilled labour, access,
design life of wall
Materials                        - range of materials, style of construction, aesthetics, cost
Construction methods    - type of construction, skilled labour, time limit on job, materials
available

IMPORTANT POINTS
water must be drained
strong and durable foundation
required correct fill behind wall angle of respose of soil
wall construction must be strong enough to oppose forces against it
approval may be required
seek engineering advice if in doubt surcharge angle
Angle of repose - is the gradient of the slope at which soil settles naturally
Surcharge angle - is the angle between the slope of soil behind the wall and the horizontal
TYPES OF RETAINING WALLS

Brick
Block
Rock - veneer (pitch) Dry stone
Boulder
Crib - concrete
Crib - wooden
Timber log - CCA, Bush log
Timber sleeper - CCA, old railway
Link wall systems - terrace block, diamond, inca, windsor
Formed concrete
Gabions
Mixed materials

FAILURE OF RETAINING WALLS

1          Breaks
2          Slides
3          Rotates
4          Weak construction - both wall and foundation
5          Water not drained behind wall
6          Poor materials

PROBLEM SOLVING

make wall construction stronger - increase material, type of material increase foundation size
slope reinforcement - shear keys, pins, geo-textile
tie backs