Application of Rigid-plastic Finite Element Method to Geotechnical Engineering

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The plastic finite element method is a numerical technique for the limit analysis of structures which requires very few The programming of the rigid-plastic finiete element method is, however, a little bit more complicated than the usual finite element method. Therefore this method is not being used popularly. The main object of this research is to show the great advantages and effectiveness of the rigid-plastic finite element method by re-establishing the theoretical background and improving the computational techniques. The findings from this research are as follows.1)Treatment of elastic regionIn the rigid-plastic finite element method, all the region is assumed to be in plastic state, which means no elastic region exists even if it is far from loading. This assumption results in some amount of numerical error and numerical instability. Therefore it is one of the problems in the rigid-plastic finite element method to solve the treatment of elastic region. In this research, we have e … More stablished the new technique for this problem by assuming the elastic region to be completely rigid without any deformation rate. This idea follows directly the theory of rigid-plasticity and can make the numerical process stable.2)Limit analysis of soil structure with groundwaterIt is general to assume that there exists the groundwater around the soil structures which affects the stability of ground severely. This is due to the fact that the groundwater changes the gravity force of the ground and decrease the effective stresses which makes the ground strength decreased. Therefore the treatment of the groundwater is essential to consider the limit state of the soil structures. Thus far no research cannot be found which combines the relationship between the critical state of soil structures and the effect of the groundwater in the limit state analysis. In this research, we have succeeded to combine the effect of pore water pressure as well as the change of gravity force with the equations of equilibrium at the limit state of the whole region. Less