A section of retaining wall on the boundary failed and posed
a safety risk. There could be a number of factors which could have contributed
to this event, namely:
a) Soil erosion behind the retaining blocks caused by fine dune sand seeping through the blocks. This erosion can be caused by storm water running over or behind blocks or by wind erosion. Gravity retaining walls relies heavily on the weight of the filling in the blocks to retain stability.
b) The section of earth behind the retaining wall that was filled above the natural ground level and the additional weight of the blocks, including blocks on the neighboring property to retain this fill, created a load in excess of what this most basic design could handle.
a) Soil erosion behind the retaining blocks caused by fine dune sand seeping through the blocks. This erosion can be caused by storm water running over or behind blocks or by wind erosion. Gravity retaining walls relies heavily on the weight of the filling in the blocks to retain stability.
b) The section of earth behind the retaining wall that was filled above the natural ground level and the additional weight of the blocks, including blocks on the neighboring property to retain this fill, created a load in excess of what this most basic design could handle.
The following steps were to taken to remedy the situation:
a) The blocks on the affected section of wall were removed and stacked aside. This included the section of blocks on the neighboring property. All excess soil was removed and stockpiled for refilling afterwards.
b) A concrete foundation have been cast, kicking unto the house foundation. Y12 steel reinforcing starter bars were inserted into foundation and spaced 400mm apart. This reinforcing extends through the blocks filled with concrete for the first 1.5m.
c) Additional blocks were filled with topsoil.
d) The sand replaced behind the retaining wall was stabilized with a 3% cement mixture.
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