Disturbed State Concept–Based Solution for Consolidation of Plastic Clays under Cyclic Loading

Abstract

This paper presents a simplified solution for consolidation of plastic clays under cyclic loading in disturbed state concept (DSC) framework. When normally consolidated (NC) clay undergoes cyclic loading, at the beginning of the loading, it is in a normally consolidated state. In each cycle of loading until the average ratio of consolidation is less than its maximum value in the last cycle of loading, the clay is in an overconsolidated (OC) state and then becomes normally consolidated. The process continues until a certain number of cycles have occurred and the clay reaches the OC state during all the loading cycles, which is called the steady-state condition. There is a gradual and continuous change from NC to OC state in successive loading half-cycles. The changing properties of the clay during cyclic loading mean that it is impossible to find a closed-form solution for this problem. Because the state of the clay changes gradually from a known NC state at the beginning to a known OC state at the final steady state, DSC can be adapted to this kind of problem using propitious state functions describing the changes in clay state. An analytical solution of a consolidation partial differential equation is used to obtain a general state function. The state function is used to describe the gradual change in state of the clay from OC to NC during successive cycles. Then the solutions of the problem in two elastic conditions of NC and OC states are interpolated using a derived state function to obtain the solution of the plastic problem. The validity of this method is ensured by a series of numerical and experimental tests.