The purpose of the paper is to develop a method for compressibility assessment of the soil base on its complete thickness strengthened with the soil-cement using the drilling-mixing technology via pressiometry testing in the boreholes. A stress-strain state (SSS) of the system “soil base – pressiometer probe – hard soil-cement elements” is considered in the process of calculation experiment for resolving the elastoplastic task of soil mechanics using PC PLAXIS 3D Foundation, and based on these data to define the optimum probe parameters ensuring maximum compressible mass versus the technical capabilities of the hydraulic pressiometers.The lateral soil deformation under the pressure, pressiometer probe sides and dimensions ratio, presence of soil-cement reinforcing elements in the foundation have been determined. Based on these data it was proved, that these dependencies, in general, correspond to the equivalent equations for stamps, and the quantitative difference between them can be adjusted by the scale factor which is established by the results of comparison of the stamp and pressiometry deformation modulus. As a result dependence was created to determine the deformation modulus of the reinforced bases relying on the pressiometry tests. The scientific originality stipulates development of the method allowing adequately assessing the compressibility of a base on the full depth strengthened with the reinforcing soil-cement elements prepared by the drilling-mixing technology.