粘土のクリープ破壊について

Abstract

Creep rupture of normally consolidated clays was experimentally investigated, perform-ing the undrained triaxial creep tests on undisturbed and remoulded Osaka clays.In the process of creep rupture, the logarithmic strain rate, dε/d log t, increases.When it attains the first critical value, a steady state creep begins. After that, the strainrate reaches to the second critical value and creep enters an accelerating region. Andfinally a creep rupture occurs with the strain rate increasing infinitely.Other investigators ~e. g. Barden (1969), Walker (1969)] have emphasized that thelogarithmic strain rate appeared in the process of secondary compression is dominated bythe effective stress ratio, particularly as failure is approached. According to their testresults including both of undrained and drained tests, it may be expressed as the expon-ential function of the effective stress ratio.When a deviator stress is applied to a clay specimen under the undrained condition, the strain rate dε/d log t increases with the increase of the effective stress ratio σ1-σ3/σm'and their relation approaches the above. When a creep rupture is expected, the strainrate during the steady state and accelerating region may be governed only by the effectivestress ratio.There is also an intimate relation between a deviator stress, a failure time and a strainrate during a steady state creep.