engleski

Numerical modelling of rock plastic yielding

The concentration of stress around the opening occurs in the excavation of an opening in the rock massif. The paper discusses the changes of stress and strains in close surrounding of the elliptical opening as well as the impact of the opening on the environment. The theoretical solution is used to define dimensions of the area where the opening causes changes in the stress condition related to the primary condition within acceptable boundaries. The comparison of the results from numerical estimates is presented according to the finite elements method with results according to the theory of elasticity. Numerical estimates were performed for the cases of assuming edge conditions: forces and displacements. The assumption of the boundary condition with displacements gives better approximation of the conditions of stresses and strains. The concentration of stress around the opening and the occurrence of the plastification zone is discussed on the case of the road tunnell excavation. The estimation is carried out according to the finite elements method using the Hoek-Brown failure criterion which is implemented into the program. The results from the stability analysis point to the area where we can expect the rock material failure, respectively the places in wich the safety measures should be provided. The zones of plastification extension are graphically presented. Especially important is the comparison of the numerical modelling results with observations on the site during excavation.

underground room; plastic yielding; finite element method

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