Dynamic Strength of Soils Subjected to Initial Shear Stress

Abstract

The purpose of this paper is to clarify dynamic properties and to define dynamic strength of soils subjected to initial shear stress for the accurate and rational earthquake resistant design of soil structures with slope. A series of dynamic triaxial tests of an actual earth-fill dam material was conducted applying static shear stress prior to the application of dynamic stress.
From the experimental results, the following can be stated: the major effect of initial shear stress is to increase axial strain significantly and to restrain the development of pore pressure; dynamic behavior can be divided into two groups according to the degree of stress reversal (for stress reversal, axial strain increases with number of cycles N; for no stress reversal, it approaches a constant value as N increases).
Furthermore, a new criterion of dynamic failure is proposed, which is based on strain rate: if strain rate increases and reaches a constant value, a soil element begins to fail. When applying this criterion to actual practice, we can not only get the accurate and rational earthquake resistant design but also prediction of dynamic failure of slopes, by the observation of strain rate or acceleration of soil elements.