Abstract: Because of the change of water ratio, the mechanical properties of swelling rock, such as the elastic modulus, Poisson’s ratio and yield limit etc., will be changed. As of the result of water ratio effect, the swelling stress, plastic flow and yielding criteria which varied with the water ratio, etc., all of these will be coupled together. This paper proposed the elastoplastic constitutive model of swelling rock based on the humidity stress field theory and by using parametric variation principle to establish the numerical variation principle and its corresponding finite element form to solve this kind of problems.

Key words: elastoplasticity, swelling rock, constitutive relation, humidity stress field, parametric variation principle