Soil stress state at the roadhead

Choosing the optimum tool shape for soil cutting is an urgent task for shaftsinking and tunnelling as well as in soil treatment for agriculture. The roadhead shape at the available load determines the stress-strain state of soil and development depth in the bottomhole area. By changing the roadhead contour, the penetration efficiency can be increased, while the feed force and tool wear can be reduced.Purpose: The aim of the work is to create the roadhead calculation algorithm and determine the stress-strain state of soil near it with a minimum number of boundary conditions, no discretization of the entire region into elements and approximation between nodes.Design/methodology: Test tasks for the proposed methodology for the roadhead and the bottom-hole area. The numerical model of the boundary conditions is based on the integral formulation of the Kelvin elasticity theory problem and uses the potential method as fictitious loads and discontinuous displacements, that makes it possible to minimize the problem with regard to symmetry, obtain a more compact system of equations and give accurate solutions at any domain point.Research findings: The assessment of the stress state of the roadhead of various shape and the bottom-hole zone of soil; loss of soil strength calculated according to the Mohr–Coulomb theory.Originality/value: The proposed method for solving the boundary value problem is recommended as an express method for estimating the roadhead stress state of an arbitrary shape in infinite regions with regard to the symmetry and implementation in Excel.