Granular material subjected to cyclic loading is characterized by the change of shear modulus, pore water pressure and volume. The change occurs when the amplitude of the cyclic shear strain exceeds a certain value, i.e. the cyclic threshold shear strain. The consequences of exceeding the threshold are reflected as cyclic phenomena: settlement, pore water pressure build-up, stiffening and degradation of stiffness. In order to investigate cyclic phenomena, it is necessary to model the force transmission in the system of grains and voids (sand), depending on the strain amplitude. The basic research tool is the numerical discrete element method. Using a three-dimensional numerical model, the laboratory simple shear test was simulated. The numerical model consists of a large number of grains (574,507 grains), and is calibrated on the basis of three curves (reduction curve, pore water pressure accumulation, hysteresis loop). Extraction and analysis of data from the numerical model takes place on several levels. At the micro level, an example of determining the stability of a single force chain is given, the underpinning mechanisms (compression, extension and flexion) are defined, and the dominant control mechanism (gradual grain translation) is also defined. At the meso level, the criteria for defining force chains were verified (mean force, angle between contact forces, length of force chain, branching of force chain). Force chains play the key role as a force transfer mechanism in granular material and they determine the mechanical properties of the material: stability, elasticity and flow. Several force chains form a strong network, the stability of which, and thus the stability of the system, is determined based on changes in: the number of force chains, the mechanical coordinate number and the distribution of contact force sizes. The propagation mode of disturbances in the system is determined by graphical analysis of the configuration of force chains depending on the strain amplitude. Two thresholds are proposed to describe the cyclic behaviour of granular material at the macro level. Accumulation threshold γt = 4∙10-5 and stability threshold γt = 3∙10-4.