COHESIVE SOIL BEHAVIOR UNDER CYCLIC LOADING IN UNDRAINED CONDITIONS

In this paper, a study of the cyclic plastic creep phenomenon during cyclic loading was performed. The plastic creep phenomena in the field of soil cyclic loading are defined as a process that occurs under a medium stress state and leads to excessive accumulation of plastic strains. Recent literature shows the existence of plastic creep, which is a part of the shakedown theory for cohesive soils. Nevertheless, when the soil is subjected to a relatively small stress state, the axial plastic strain may occur as a phenomenon called abation, where plastic strain increment occurs in a constant decreasing manner. Cyclic triaxial tests were performed to understand the abation. The results indicate a specific phase in soil response, such as pre-failure stages marked by pore pressure increase and subsequent effective stress reduction, indicating a steady state during repeating loading. In this paper, the proposition of a cyclic plastic creep mechanism based on test results is presented. The soil response was divided into three phases based on the pore pressure, stress paths, resilient modulus, and plastic strain change analysis.