2019 年 7 巻 2 号 p. 505-515
Desaturation is an effective ground improvement for mitigating liquefaction-induced ground failures. This paper aims to discuss numerical capabilities for simulating the undrained cyclic behavior of desaturated silica sands. The laboratory experiments were initially conducted to investigate desaturation effects on medium dense desaturated silica sand behavior (Dr=60-65%, Sr=91-100%) under undrained triaxial loading conditions. Desaturation was achieved by injecting micro-bubbled water. The experimental results showed an increase of the angle of a phase transformation line, ϕpl, in 4-5˚, no desaturation effects on the angle of a critical state line, ϕcl, and less degradation of Young modulus comparing to the saturated condition. The numerical analysis was secondarily performed to simulate the experimental results using LIQCA2D17. The comparisons to the preliminary experimental result showed that failure criteria were critical on stress-strain behaviors, and the Yasufuku criterion was suitable for both saturated and desaturated conditions. The desaturation effects were further discussed. The desaturation critically affected the stress-strain behavior after the stress path reached the phase transformation. The desaturated silica sands exhibited continuous modulus reduction although the specimens were fully liquefied (i.e., EPWP ratio nearly equaled to 1.0). Liquefaction of those desaturated silica sands was characterized as "slowly flow deformation."
