Yield displacement factor for buried line

currently i performing buried line.
i like to know more about yield displacement factor ? is it we should modify the values based on the soil depth in calculation. or caesar will modify according to soil depth .
regards
remesh

C2 will use this value to calculate the elastic limit of the soil. Your value for the yield displacement factor will be multiplied by the buried depth to top of pipe to set the limit to elastic displacement. The soil ultimate load is divided by this elastic displacement to set the initial soil restraint stiffness K1.