Theoretical determination of the expansion forces of the technological cavity in the soil by wedge-prismatic and conical-cylindrical working bodies

Abstract


 Problem. The article deals with the problem of expansion of the technological cavity in the soil (TPG), previously obtained by the method of controlled static piercing, for the laying of underground linear extension objects (LPO) of urban communication networks. Group laying of communications in one cavity requires large holes, which in turn leads to a significant increase in the workforce and dimensions of work equipment. The only way out of such a situation is the use of working bodies (RO) of wedge-prismatic form, gradual expansion of the hole in several stages and change of soil moisture in the walls of the hole cavity. Goal. The main goal is to create a methodology for engineering calculation of the parameters of the wedge-prismatic working bodies and to determine the static expansion efforts of the TPG based on the known initial data on the soil and the shape of the RO. Methodology. The study is based on the theory of the invariance of soil mass before and after piercing. In the process of expanding the TPG to the required size, the density of the soil medium changes from its natural value to a solid state, after which the soil simply moves to a certain distance from the axis of the cavity, compacting the neighboring massifs. Results. The hypothesis of the interaction of wedge-prismatic tips with the soil during static puncture is substantiated based on the determined law of soil density change along the thickness of the wedge-prismatic tip. Originality. The theoretical dependences for determining the rational parameters of the RO of wedge-prismatic form, the resistance of the sequential expansion of the TPG for the LPO after the starting passage of the leading hole, or the cavities of the primary expansion were obtained. Practical value. A method of determining the penetration force of the TPG for LPO after the leading pass is proposed, taking into account the elastic (reverse) deformations of the soil, its moisture, the shape of the RO, and the characteristics of the power equipment, as the difference between the full and pilot resistance of the soil puncture, as well as recommendations on the possibility of reduction o these forces by changing the shape of work equipment or soil moisture.