An Improvement of the Commonly Used Yield Function for Rock Material

In this paper the convex condition of the yield function in π-plane is discussed. A new yield function which has no corner in π-plane, and can always keep convex is proposed. It is more approximate to Mohr-Coulomb yield function than Drucker -Prager yield function. Hence this yield function has some advantages of the above yield functions and can avoid their disadvantages.