EFFECTS OF INITIAL SHEAR STRESS AND VIBRATION FREQUENCY ON THE DYNAMIC STRENGTH CHARACTERISTICS OF SATURATED CLAY

Abstract

Initial shear stress is inevitable in actual engineering slopes, subgrades and foundations. The soils exhibit different dynamic characteristics under an initial shear stress. The dynamic strength characteristics of saturated clay under cyclic loading were studied through a dynamic triaxial test of remoulded clay in the Wenchuan area. The effects of the failure criterion, initial shear stress and vibration frequency on the dynamic strength characteristics of saturated clay were also analysed. The results showed that the strain failure criterion with a strain value of 2.5 % or the transitional strain ε_tp can reflect the soil damage realistically and evaluate the dynamic strength of the soil objectively. ε_p = 2.5 % can be used to replace ε_p = ε_tp when the dynamic strength parameter of the saturated clay was calculated under seismic loading equivalent failure vibration times. The dynamic strength parameters of the saturated clay under different earthquake magnitudes were calculated by introducing the equivalent failure vibration times of the soil under seismic loading, thereby providing data support for the stability analysis of the clay foundation under seismic loading. The initial shear stress and vibration frequency have a considerable effect on the dynamic strength of saturated clay. Under the same vibration frequency, the larger the initial shear stress is, the smaller the required dynamic stress is for the soil to break, and the smaller the dynamic strength parameter is. The existence of the initial shear stress reduces the dynamic strength of the soil. Under the same vibration times, the higher the vibration frequency is, the greater the required dynamic stress is for the soil to break, the larger the dynamic strength parameter is, and the greater the dynamic strength of the soil is.