Shallow brick arch near failure

If you see this cracked and or without any steel lintel in place look out
(2.8m clear span attempted!)

The brick arch arrangement here is close to failure.  The single isolated pier on the LHS of view is rotating outward and cracking 10mm wide or more is well developed near midspan at the centre of the arch soffit.  This now requires propping until its removal and reconstruction is complete.  

Footing suitability to control seasonal movement within a restricted range that a masonry arch could handle would be akin to the volume of an iceberg below the water level (with reactive Brisbane clay soils)