ELASTIC AND KINEMATIC HARDENING PLASTIC BLAST INDUCED DEFORMATIONS OF UNDERGROUND TUNNELS B)I THE FINITE ELEMENT METHOD
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Abstract
This research deals with the stress analysis of typical underground tunnels using isoparametric finite elements. Enhanced soflware is used for predicting and analyzing this behavior by using a single phase formulation. This software was developed from an original Computer code namea MXOYN The finite element method is used to solve the dynamic equiiibrium equation with step-by-step tirre
integration schemes. A selected type of dynamic load was chosen which is blast loading. Frictional and paniculate materials, i.e., concrete and soil, are considered. The soil and concrele structures arc analyzed where a dynamic elastic model for concrete and a linear elastic one for soil are used. The soil is further analyzed by a bounding surface plasticity model. Tlie stress wavcs havel and the reflection effects especially in the no tension materials, i.e., soil are investigated. The effects of blast loading are then analyzed hypothetically placing the explosion at the grourd surface. The stresses and displacements are computed at different sections.
The nonlinear analysis utilizing the bounding surface plasticity characterization gave better predictions over the linear elastic model. The linear elastic model is proposed to be used as a first prediction of the problems encountered, but it is incapable of realizing the actual behavior under dynamic loads.
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References
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