There are a lot of papers about dilatancy, it is typical for the majority of highly concentrated dispersed systems. A three-dimensional deformation in the active zone of such systems is contraction and deformation by dilatancy. An increase is called dilatancy, a decrease is called negative dilatancy or contraction. The violation of soil strength due to a shift in one of the ground on the other is the most common fracture in the construction of excavation slopes. In this paper, we use a model similar to the model of a perfectly plastic body. The construction of a computational algorithm is based on sampling the computational domain in the finite element method. The modeling of soil is based on specific strength properties which determine its bearing capacity. They include the cohesion coefficient, the angle of internal friction coefficient and dilatancy coefficient, which characterizes soil loosening or compaction under deviatoric loads. The paper considered a number of model problems of elastic-plastic deformation of a dirt mound, studied the convergence of the solutions. It may be noted that the inclusion of the dilatancy decelerates the mound transition to the limiting state, and thereby a second band slip is forming. The implemented methodology allows the calculation of elastic-plastic deformation of soil masses, complying with the law of dry friction with and without dilatancy.