Author(s): B. Ladanyi; J-R. Murat; P. Huneault
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Keywords: No Keywords
Abstract: The stage-loaded borehole dilatometer test, introduced into frozen soil testing by Ladanyi and Johnston (1973), has since that time been used with success in several field studies, both in frozen soils and in ice. The procedure for determining the creep parameters from such tests as originally developed, is based on the assumption that the material around the borehole has attained the state of stationary creep at the end of each loading stage. However, if a dilatometer test is performed in the sea ice, which can be described as a linear-elastic non-linear-visco-plastic material, it is found that a certain amount of time after load application is necessary for the stresses around the borehole to redistribute from their initial elastic state, to their final state, corresponding to the stationary creep. Although, theoretically, this time is infinite, in practice, it is found that, after a limited time interval, the stresses will come so close to the stationary state, that the resulting errors in the determination of creep parameters will become tolerable. This paper presents a finite element simulation of the borehole dilatometer test in the creep range, using a set of material properties, pertaining to those found for sea ice. A parametric study was then performed in order to evaluate the minimum time under load required to achieve a given precision of results. The study enabled some improvements to be made in the original data analysis procedure.
Year: 1984