Coupling pore-water pressure with distinct element method and steady state strengths in numerical triaxial compression tests under undrained conditions |
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| Authors: | Yasuhiko Okada Hirotaka Ochiai |
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| Institution: | (1) Incorporated Administrative Agency, Forestry and Forest Products Research Institute, 305-8687, Matsunosato 1, Tsukuba, Ibaraki, Japan |
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| Abstract: | The undrained shear behaviour of sands has been a key topic after the devastating geo-disasters during the 1964 Niigata Earthquake
in Japan. Extensive geo-technical soil tests, especially undrained triaxial compression tests, have revealed that the liquefaction
phenomenon was the major cause for the disaster expansions. To numerically reproduce the liquefaction phenomenon, the pore-water
pressure was coupled with a distinct element method. In this model, the dynamic changes in pore-water pressure were taken
into consideration by the changes in volumetric strain and modulus of compressibility of water in the respective measurement
spheres. Fluid-flows among the measurement spheres were controlled by Darcy’s law. The effective stress paths and steady state
strengths in undrained triaxial compression tests associated with the wide ranges of initial void ratio were investigated.
The effective mean stresses of medium-dense to dense numerical specimens at the steady state were negatively proportional
to the initial void ratio. Loose numerical specimens reproduced quasi-liquefaction with the effective mean stresses that were
less than 25% of the initial value. The medium-dense numerical specimens reproduced the phase transformation that was a typical
characteristic of granular materials. The rolling restraints did not much influence of the effective angle of internal friction
but strongly affected pore-water pressure behaviour within a certain range of initial void ratio. |
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| Keywords: | Fluid-coupling Distinct element method Pore-water pressure Steady state strengths |
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