Realization of uniform deformation of soil specimen under undrained plane strain condition based on soil water coupled finite deformation analysis considering inertia forces

Based on a soil water coupled finite deformation analysis, theoretical considerations and numerical calculations were carried out under the undrained plane strain condition in order to reproduce a uniform deformation field. Rather than the "quasi-static" equation of motion, which does not include inertia forces, a dynamic equation of motion which includes inertia forces was used At first, a theoretical consideration was carried out to realize uniform deformation for a saturated soil that satisfied the element-wise undrained/constant-volume condition. This presents an "infinitely slow loading" case without ignoring the inertia term based on the u-p formulation. In other words, it can be seen that under general slow loading that is not infinitely slow, a gradient in the pore water pressure will always be produced, resulting in the migration of pore water and loss/collapse of uniformity. This first conclusion is useful for verifying numerical analysis code made in the finite deformation regime. Next, the uniform deformation of a plane strain rectangular soil specimen was measured under constant cell pressure and undrained boundary conditions using a dynamic soil water coupled analysis in which the SYS Cam-clay model was employed as the elasto-plastic constitutive model for the soil skeleton. In addition, the effects of the loading rates as well as loading applications, with/without inertia forces, on the loss of uniformity in deformation were shown to have a significant influence on the inertia term even though the loss itself was extermely small. (C) 2013 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.