Shape of Yield Curves on a Deviatoric Plane in Soil

Abstract

The failure criterion examined using fracture state says that Mohr-Coulomb criterion is more appropriate to soil than Mises criterion. The important aspect which must be confirmed in the examination of the criterion is that the stress state at fracture are situated on a critical straight line in primary yield relation showing the dependency between equivalent deviatoric stress and hydrostatic pressure. Moreover, the equivalent deviatoric stress must be representative of the magnitude and shape of the yield curve on a deviatoric plane. Therefore, the critical straight line is also affected by failure criterion itself. Such mutual dependency makes it complicated to find out the relevant yield criterion. For the discussion of the yield criterion, we used the data obtained in the compression tests performed by Reades & Green and by Lade & Duncan. First, on the assumption that fracture stress points are situated on the critical line in the primary yield relation, the shape of yield curve on the deviatoric plane is examined. Then, the curve shape is represented with the relation between J2 and J3 where J2 and J3 are the second and the third invariant of deviatoric stress respectively. Second, the equivalent stress is defined using the curve shape relation. Third, it is confirmed that fracture points in primary yield relation are located on the straight line when based on the equivalent stress defined