Use of a non-associated flow rule for determining the stability of a vertical circular excavation

An axisymmetric lower bound limit analysis technique in combination with the finite elements has been used to investigate the effect of considering a non-associated flow rule on the stability number (γH/c) for a vertical circular unsupported excavation in a general cohesive–frictional soil medium, where (1) H is the excavation height, (2) γ defines the unit weight of the soil mass, and (3) c indicates the cohesion of the soil mass. The results are derived for different magnitudes of dilative coefficient (η), friction angle (?), and normalized excavation height (H/b), where b = the radius of the excavation. The results clearly indicate the increase in γH/c with an increase in η value. It is expected that the charts provided in this note will be quite helpful for the practicing engineers.