Urgent safety inspections of hazardous reservoirs have been conducted in Japan. The undrained cyclic triaxial test is used to evaluate the dynamic strength of embankment soils during earthquakes. In general, the initial static shear stress acts on the slope of an embankment. Furthermore, the embankment soil of a reservoir is subjected to various effects such as initial shear stress, seepage flow, deterioration, and cementation due to aging. Although it is important to consider these factors when evaluating the dynamic strength characteristics of embankment soils, these effects have not yet been examined in detail.
This study used the undrained cyclic triaxial test to elucidate the effect of initial shear stress on the undrained cyclic behavior and strength characteristics of three types of embankment soils. In addition, cyclic triaxial tests were conducted under different confining stress conditions. The soil samples used were sand and silt with plastic or non-plastic fine fractions. The main conclusions of the study are as follows: 1) For an embankment soil consisting of non-plastic fine fractions, liquefaction occurred under isotropic confining stress conditions. 2) For all types of embankment soils, liquefaction did not occur under initial shear stress conditions and the effective stress path reached a steady state. 3) The cyclic shear strength of embankment soils slightly increased with increasing confining stress. 4) The fine fraction content is an important parameter for evaluating the cyclic shear strength characteristics of embankment soils subjected to initial shear stress.
View full abstract