This paper focuses on the basal stress distribution and depression of stress of sand prism. The sand prism is divided into a stress known zone I and a stress unknown zone II based on the fixed principal axes (FPA) assumption. On several shear stress distribution assumptions

the stress state of zone II is available. The values of coefficient of earth pressure at rest on the sand centerline on different shear stress distribution assumptions are compared to the one proposed by Kulhawy. The following results are achieved; there is depression of normal stress on the base of sand prism

and the larger of the friction angle (the denser the sand prism) is

the more the depression of normal stress is; and the larger of the depression range is; the shape of the stress distribution and minimum value of normal stress and the location of the minimum normal stress are different on different assumptions; and the assumption of quadratic distribution and cubic distribution of shear stress are most reasonable.