NUMERICAL SIMULATION OF SAND SUBJECTED TO CYCLIC LOAD UNDER UNDRAINED CONVENTIONAL TRIAXIAL TEST

In this paper, based on a elastoplastic model that can properly take into consideration the influences of the density, the structure formed in depositary process and the stress-induced anisotropy of soils, 2D and 3D finite difference-finite element analyses considering the soil-water coupling problems are conducted to simulate element test of sand specimen subjected to cyclic load under different loading conditions in triaxial test using the code named as DBLEAVES. In the element test, through stress-strain relation is regarded as uniform within the specimen of soil, it is usually non-uniform in reality. Due to limitation of element test devices for soils in laboratory test, a perfect element test is impossible in reality due to some factors such as an initial imperfection of test specimen, friction between loading plates and specimen, gravitational force of specimen and etc. It is, therefore, necessary to answer the question whether the results of an element test commonly used in laboratory test are convincing in determining the mechanical behaviours of the soils. If the answer is yes, then how much is the influence of these factors on the tests which is usually regarded as an element behaviour. In the simulation, the element is considered as a boundary value problem. The influence of those factors such as amplitude and frequency of cyclic loading, confining stress is also considered in detail. In the simulation, all values of material parameters are kept the same, which makes the numerical simulation being meaningful.