| A new analytical tool is developed and used in this thesis, to study the static and cyclic stress-strain behavior of granular soil.; The tool is a computer program named CONBAL-2. It combines the general solution of the Hertz-Mindlin contact problem for two rough, elastic identical spheres, developed at RPI (CONTACT), with the computer code originally developed by Cundall using the distinct element method and a three-dimensional periodic space without boundaries (TRUBAL). CONBAL-2 can calculate the response of two-dimensional random arrays of spheres of the same size or different sizes, which can slide with respect to each other, but cannot rotate, and which can form new contacts or destroy old ones. The program was used to study the monotonic and cyclic stress-strain behavior of sand under a variety of loading conditions which included monotonic drained and constant volume (undrained), and cyclic constant volume conditions. In these numerical simulations, the soils were represented by 2-D random arrays of as many as 531 elastic, rough quartz spheres. The results of these simulations were compared with available experimental data on actual sands, including studies on the effect of particle size distribution, porosity, consolidation pressure, stress path, and number of contacts per particle. This included stress-strain and volumetric strain response (dilation) computed for the drained simulations, and stress-strain, "pore pressure", moduli, damping ratio, and threshold strain computed for the monotonic and cyclic constant volume simulations. Very good agreement was generally found between the results of these numerical experiments and the actual laboratory measurements. Much additional insight was provided by the statistical information on the microscopic behavior at the interparticle contact level, which was obtained and related to the macroscopic behavior. All these results reveal that CONBAL-2 can be used as a reliable tool to study the behavior of granular soils. |
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