question about "Extended Dracker Prager plasticity model"

Hi my friends,

i am using Dracker Prager Plasticity model in abaqus 6.6, i am working on rock sample, this rock sample shows strain softening behavior not strain hardening, but you know that Drucker Prager can simulate both hardening and softening.

i have the stress-srain diagram from the laboratory test. 

 my shear criterion is linear, i choosed from Suboption   Drucker Prager Hardening.

my problem and my question is:- how can i convert the stress-strain diagram to the hardening table, this hardening table contains Yield stress and Abs. Plastic strain.

i think this Yield stress in case of rock is like cohesion, is it right?? how can i fill out the table which composed of YIeld stress and Abs. Plastic strain???.

any body work with Drucker Prager can help me please.

Best regards, Gamal