if you are not academically interested in finding ko, normal ka coeff. shall do for design purpose. You should be clear about the drainage conditions of soil to estimate accurately bulk unit wt., coeff. of friction and cohesion. I think this will be sufficient.
gr
For normal conditions and structures the very basic coeff. of Ka is sufficient for design purpose. You should clearly see the drainage conditions of soil so that realistic estimates of unit weight, cohesion and friction coefficients are made.