Traditional procedure defines the required penetration depth for stability as the depth that satisfies
the static equilibrium at limit state condition as shown in fig.(1). In order to achieve safety factor of 1.5 to 2.0,
traditional procedure recommends increasing the calculated required depth by (20% to 40%)[1].
Since the soil unit weight (γ) is the same on both sides of the wall, hence, the required penetration depth (D) depends
on internal friction angle of soil (φ) and depth of excavation (H). The relation between those variables is summarized
graphically in the chart shown in fig.(2).[1]. Since this study is concerned in dry granular soil, hence, depth of ground
water table factor (α) is always considered zero.