In recent years, pile-plate foundations have been widely used in civil and industrial construction all over the world. When the grillage is turned on, the bearing capacity of the foundation increases, and the growth of sediment slows down. The article provides a study of the nature of pile-slab foundations and the development of an engineering method for calculating a slab grillage, taking into account the actual operation of the foundation and an analysis of the stress-strain state of combined pile-slab foundations from the general design scheme of interaction of the pile grillage of the soil. A finite element model of the calculation scheme was used to conduct numerical experiments, calculations were carried out to study the operation of slab grillages in pile-slab foundations, and an analysis of numerical experiments was performed. The experimental data show the role of a low grillage in the bearing capacity of pile foundations, and the results obtained serve as proof of the qualitative nature of joint work with the soil of pile foundations when resting the grillage on the base.