Elastic-viscoplastic solution of a circular tunnel in Hoek-Brown rock mass

A closed-form analytical solution to rheological phenomena is obtained based on Hoek-Brown (HB) yield criterion and the generalized Bingham model. Once circular tunnel excavated, an initial plastic region formed. When total stresses fulfil condition, steps into viscoplastic region, in which displacement develops with time. The one-dimensional constitutive equation of model transformed a three-dimensional expression polar coordinates by combining plane strain condition. With help equilibrium differential equation, geometric boundary stress can be expressed. At moment t, displacements are described similar solutions elasto-plastic state. stresses, strains after transformation expressed region. proposed was verified tunnels elastic-brittle-plastic rock mass.