<p>The article presents the theoretical research of the authors, into the impacts of directions of seismic waves on the stability of the soil base structures. The study into the interaction of wave directions and critical acceleration of the soil, at an account of physical and mechanical properties and levels of moisture of the soil, has proposed a formula that is believed to be good for designers and builders. It can be used to determine the stable state of a soil particle against <br /> shear located at any point of the soil mass. At the same time, the proposed formula also allows us to generally assess the conditions of the limit state of the fluctuating soil layer. The formula helps to trace the dependence of the critical acceleration of the soil, in addition to the friction forces between the particles, and on the adhesion forces and pressure from the load acting on the soil. In this case, the seismic stability of the thickness, in general, rises with increasing soil strength and falls with increasing soil thickness. To prove this, the paper shows an example of solving a specific problem.</p>