In active state of plastic equilibrium in a non cohesive soil with horizontal ground surface

ANS:C - major principal stress is vertical

Major principal stress is vertical. In the active state of plastic equilibrium, the soil mass is undergoing failure due to external loading or other destabilizing factors. For a non-cohesive soil with a horizontal ground surface, the major principal stress will generally be vertical, acting perpendicular to the ground surface. This vertical stress contributes to the shear stress along potential failure surfaces within the soil mass. The minor principal stress, in this case, would be horizontal and acting parallel to the ground surface. This stress configuration is typical in soil mechanics for soil slopes and embankments subjected to gravitational loading.