In the framework of limit analysis, the assumption of an associated flow rule with the dilatancy angle in any point equal to the friction angle φ, is necessary for the derivation of the fundamental theorems of this theory and to provide rigorous bounds of the critical load. This associated flow hypothesis does not necessarily represent the real behaviour of geotechnical materials so that, in general, the dilatancy angle tends to be lower than the friction angle.
While it is not possible to get rid of this assumption in our analytical mechanism, it is possible to evaluate its influence on the results by dealing with two limit cases in our numerical simulations: an associated flow rule and a zero-dilatancy behaviour.
The key task is to evaluate the validity of this assumption for the problem studied.
Numerical results provided in Table 1 show that this assumption has actually a limited influence on the value of the critical collapse pressure, so that the theoretical background of limit analysis is therefore acceptable in this case.