Problemy teorii mechanicznego urabiania gruntów

Discussed are the problems resulting if an attempt is undertaken to build the mathematical theory of the mechanics of earthmoving processes with the use of heavy construction machinery. Discussed are problems of the choice of the most suitable limit state criterion for stresses and of the respective relations between the stress and strain-rate tensors. It is pointed out that, at present, the inertia forces and strain rate effeets cannot be accounted for in solutions of practical problems. Another difficulty arises from the fact that if the stress-strain curve for a given soil is unstable, the deformation during earthmoving process proceeds in a non-continuous manner. Presented are several quasi-static solutions for some practical processes. The rigid-plastic model of the material without instability in the stress-strain curve has been assumed. A non-associated flow rule assuming incompressibility and isotropy of the soil has been introduced.