Page 20 - Landscape SA 102

ALLIED TRADE FEATURE

Fuel Street Park in Westbury, Johannesburg, where a play area with seating was created. Remacon’s precast stadium seating system was
used, comprising two different precast concrete elements. When combined one above the other, they create a seating arrangement to any
slope angle required. Access stairs were also incorporated.

be prevented by increasing the foundation awkwardly, sometimes resulting in broken fills, and are largely based on BS 8006. The
depth below ground level. Subsoil water legs. Occupational Health and Safety Act must
in the soil behind the wall will cause an also be considered.
increase in weight as well as lubrication The earth embankment to be retained is
of the soil particles, and this can lead to at its most precarious just before the wall Are there areas that are
serious problems for the safety of the wall. is installed, when it is unsupported and considered unsafe for putting up a
exposed to the elements and vibrations retaining wall?
In the case of reinforced earth walls, of compaction equipment. Light rain will
these are designed to include geofabric saturate the soil, making it heavier, and any SF: Yes, retaining walls in or near water,
reinforcing behind the wall, which greatly machinery or equipment parked on top of such as dams or rivers, are high risk.
increases the stability of the retained soil. It the embankment will impose additional
also binds the wall blocks to this stabilised loading that it may not be able to support. SD: An engineer will design the wall
mass of soil so they both become part of to be safe by considering the entire
the design. For very high walls, the design Safety measures to be taken can include environment. For low walls that do not
is predominantly in the stabilised earth wearing hard hats, steel-capped shoes require an engineer’s certificate, it is best
and the blocks act as little more than and using transport carts and lifting tools to avoid the following conditions: a wet
covering to prevent erosion of the soil for carrying heavy loads. environment with excessive subsoil water,
structure. highly expansive clays and non-cohesive,
HR: When an area is deemed unsafe for sandy soils.
HR: Considerations such as basic loading, constructing a wall, the engineer will
slope stability, soil properties on the not go ahead with the project. Statutory HR: An experienced engineer will design
site, selection of backfill, effect of the regulations and public safety concerns a safe retaining wall, irrespective of its
surcharge loading and control of surface must be followed. In South Africa, height. If that is not possible due to site
and subsurface water all need to be taken SANS 208 of 2011 and 508 of 2008 are characteristics, he will seek alternatives
into account. applicable. These encompass the design that can work.
and construction of reinforced soils and
What safety aspects are taken
into account for constructing and
installing the wall? Terraforce round-face finish erosion control measures in Langebaan, Cape Town
SF: All standard safety requirements must
be adhered to, especially when cut faces
are constructed against, to check that there
are no cracks in the soil above that may
cause damage. Temporary stormwater
controls are also often necessary to
prevent stormwater from washing onto
the walls being constructed and causing
damage to them.

SD: For high retaining walls, lifting heavy
blocks from the bottom to the top or vice
versa, is difficult. Fatigue and mistakes
can result in a block being dropped from
a greater height, and perhaps landing on
a person’s head. Specific planning must
be done to prevent these accidents and
fall protection needs to be in place as
often, a wall builder can be so focused on
his work that his footing slips and he falls

18 Landscape SA • Issue 102 2021