The determination of the total resistance to penetration of the annular drill into the soil is based on the concept of changing the elastic state of the soil during its compaction, which is defined by the compression modulus of soil deformation. This parameter comprises all the physical and mechanical properties of each type of soil and makes it possible to specify the laws of the normal pressure of penetration resistance acting on the surface of the conical and cylindrical parts of the working body.The proposed theoretical models of processes occurring during penetration of the annular drill into the soil gives an opportunity to determine the influence of the parameters on the resistance force for each working procedure, depending on the physical and mechanical properties of the soil. It has been found that the maximum length of the annular drill is determined for the conditions of soil movement (unplugged condition), which, for example, with a cylinder diameter of 28 mm, is 0.87 m, 1.04 m and 1.16 m respectively for sandy clay, semi-solid loam and tough clay. It is now clear that a 2-fold increase in the internal diameter leads to an increase in the core length of 1.75 times.It has been determined that the two-cone drill does not facilitate passage of soil through itself and it causes soil plugging as well as formation of soil plugs on the frontal planes, which leads to an increase in drag force. Therefore, to provide unplugged conditions during pipe jacking, the drill with a single external cone should be used.The obtained results of the work can be used to substantiate the rational parameters of the working equipment for creating a horizontal borehole in different types of soils.
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