Earthwork is performed by some digging machines: excavators, scrapers, graders, dragline excavators, ditching machines, boring installations, etc. Some researchers were engaged in the cutting of soil, and in general, the theory of cutting of soil is rather developed. However, its provisions are correct to the determination of machines of the soil performing almost rectilinear cutting close to a surface, in a dehydrated medium. As practice shows, the known provisions of the theory of cutting do not allow to calculate accuracy the mode and loading of these machines. This article is devoted to the establishment of the regularities determining soil resistance to destruction for construction boring and milling machines. The determined dependencesdetermining the law of change of a corner of a chip when cutting soil as a function from the coupling, pressure in soil, hydrostatic and hydrodynamic pressure upon a surface, the angle of cutting, the angles of internal and external friction are determined. Coefficients of working conditions which describe a high-quality picture of cutting of soil are received and give a ratio of forces in case of rectilinear destruction of soil to forces arising in case of its milling.