Retaining Wall Failure

Forster

In mid-2006, a local structural engineer prepared a report and specifications for a 3.5 m high segmental block, concrete retaining wall on a cut / fill industrial site near Foster NSW.  Subsequently, the retaining wall was constructed without engineering review.

Later, in late 2010 the local civil / structural engineer inspected the site, noted that the wall had not been constructed in accordance with its specifications;  as such, remedial works were recommended.  Later, in early 2011 the remedial works were undertaken and the local civil / structural engineer certified the adequacy of the remedial works, on the proviso that the owner of the retaining wall completed certain drainage works on the retaining wall backfill within a short time frame.

Subsequently, in mid 2011 a large rain event occurred which caused a small movements of the retaining wall and associated significant seepage from the wall’s subsoil system.  Later:

  1. Two further heavy rainfall events took place within the next 2 months.
  2. A third heavy rainfall event occurred as the drainage works were being completed.
  3. The retaining wall collapsed shortly after the third rainfall event in September 2011, with subsequent extensive damage to the factory building on the adjoining land.

In the ensuring litigation, allegations were made against the local civil / structural engineer, with the main allegation being one of faulty design by the local civil / structural engineer.  The allegation was also supported by expert evidence from another local engineer and local geotechnical engineer / geologist.

SCE were then engaged to investigate the matter on behalf of the local structural engineer.  These investigations ‘in essence’ determined that although there were a number of shortcomings in the local engineer’s design, that the true cause of the collapse was the failure to install effective surface drainage prior to the major rain events of June, July, August and September 2011.

Whilst the matter was subsequently strongly contested, during the ensuring mediation processes, the SCE view as to the true cause of the collapse was accepted and provided a pathway for commercial resolution of the matter.

Retaining Wall Failure | Shirley Consulting Engineers

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