The slip surfaces paralleled to each other

which are assumed to be inclined at an angle ? to the horizontal is taken to be the analytical element. Based on the theory of main stress axes rotation

the theoretical formulae of the vertical stress considering the inclination of the slip surface and soil arching

the earth pressure coefficient considering the inclination of the slip surface and the angle between soil and slip surface are obtained by considering equilibrium of the horizontal and vertical forces acting on the analytical element. The results show that the theoretical formulae are rational by comparing the computed results using the proposed method with the results obtained by the existing methods. A parametric study is undertaken to investigate the effect of various parameters involved in the proposed analytical expression; the results obtained reveal that for cohesionless soil

the vertical stress increases with the depth linearly for shallow depth

then increases with the depth slowly until reach some depth; the vertical stress remains constant. The vertical stress increases with the increases of inclined angle and the stope width due to the weakened of soil arching effect

decreases with the increase of the friction angle between slip surface and soil. The earth pressure coefficient increases with the increase of the friction angle between slip surface and soil

but decreases with the increase of internal friction angle of soil.