3. SIMULATIONS
All the analyses were performed using the parameters of Tsukidate volcanic sand (non-plastic sand), which has a specific gravity of 2.478 [9] (Tables I and II). In the simulation of the cyclic triaxial tests for the calibration of the model parameters and validation of the model, three types of initial shearing states were considered (Table III). Saturated soil was used in case c-1, while unsaturated soils having different degrees of saturation were considered under varying pore air pressure in cases c-2 and c-3. Then, cyclic shearing, for which the axial strain amplitude was increased every 10 cycles as shown in Figure 3, was applied to the specimens under the fully undrained conditions at a constant confining pressure.
3.1. Fully undrained simulation
The fully undrained condition, that is, unexhausted air and undrained water, is the condition where air and water are unable to drain out of the soil. In other words, the mass of water and air are constant. So as to simulate the unexhausted air condition, we assumed that air is an ideal gas, and the temperature is constant. Therefore, Boyle’s law, which states that the absolute pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature, can be used as where ua is the pore air pressure and Va is the volume of pore air. As the volume of soil particles, Vs, is constant, we obtain A classical equation for solving problems involving three-phrase relationships (solid, water, and air) can be used to satisfy the undrained water condition as where w, e, and Gs are the water content, void ratio, and specific gravity of the soil particles, respectively. As Gs is constant, we get For the detailed procedure of the simulation, please refer to the Appendix A.
