In PLAXIS 2D 2010, in random cases there was a problem with the calculation of consolidation phases in models with 15-noded elements (in the classical and advanced mode). You will notice that the consolidation phase fails/stops directly at the start of calculation or does not start calculation at all. This behaviour is the result of a bug in the calculation kernel.
This has been fixed since PLAXIS 2D 2011.00
The following workarounds are available: