Shoring System Failure

Rushcutters Bay

During 2008, a large development for three ‘mixed use’ buildings in Rushcutters Bay was under construction which included a 6 to 8 m deep excavation in the sandy alluvial soils.  In order to make the excavation, an anchored sheet pile shoring system was installed.

Unfortunately, the sheet pile shoring system was inadequately designed & specified, and as a consequence of a failure involving large displacements and settlement of the retained alluvial soils occurred.  These movements resulted in:

·          a neighbouring mechanics workshop displacing or ‘walking over’ the property boundary so that it was now located on the construction site property;

·          differential settlement of the footing system of a historic building [constructed 1942], with consequent significant cracking to the buildings brickwork.

As a consequence of this failure, SCE were engaged by the developer to advise on:

a)   The cause of the shoring failure & movement.

b)   Whether the historic building could be repaired and retained, or whether demolition was required.

SCE’s assessment of the shoring failure was that the design was inadequate due to:

1.    The inadequate depth of the steel sheet pile shoring system.

2.    An inappropriate anchor specification that resulted in and overstressing of the anchors.

Finally, in relation to the historic building whilst discussions and possible designs were discussed with several specialist contractors, it was ultimately determined that the building could not be repaired, with the consequence that the developer was required to demolish the building, and then rebuild it in exactly the same form as the original construction.