The performance of a turboshaft engine derives essentially from the performance of the turbine, which in turn is closely correlated with rotor/stator clearance at the blade tips. In this article we propose to define criteria for qualifying turbine architectures based on a geometric model which integrates variability due to the processes of obtaining parts, the assembly processes and the thermomechanical behaviour of the turbine. The geometric model proposed here integrates thermomechanical strains in 3D dimension-chains formalised by operations on polytopes (Minkowski sum and intersection).