In this equation, (q) is the overhead pressure in the soil part (see Fig. 6b), (h ) is the depth of soil at the desired point and View the MathML source, which is known by Parandtl equilibrium coefficient. ka can be obtained from Eqs. (1), (2), (3) and (4). If the soil is cohesive, two forces act on the rock column: a friction force with angle (δ) and the normal vector to rock column with the amount (E), which is defined by Eq. (6). The other force is the result of cohesion between soil and rock (α) [32]: