Analysis of sedimentation/consolidation by finite element method

Abstract

Abstract A low concentration of solid suspension material is transformed into a soil layer through two stages of sedimentation and consolidation, occurring simultaneously. During sedimentation in the uppermost part of the problem domain, in the rest of the domain, the soil particles form a continuous structure, the ‘Terzaghi soil’ so called. This soil structure consolidates under its own weight and the weight of the upper part. Because of the formation of this structure, a discrete boundary separating sedimentation from suspension is formed. On this boundary, termed a ‘shock boundary’, kinematic shocks occur. In order to analyze the phenomena of sedimentation/consolidation by finite element method, in this study, the sedimentation was considered as a solid flux problem from the standpoint of the Eulerian coordinate system; while the consolidation was considered as a fluid flux problem from the standpoint of Lagrangian coordinate system, with keeping the shock boundary between them. From this basic understanding, a program for one-dimensional analysis of sedimentation/consolidation was developed using the finite element method. In the program the governing equations were separately applied — continuity equation only for sedimentation; and continuity and force equilibrium equations for consolidation. Nevertheless, the interaction between them was continuously accounted for by keeping track of the shock boundary. From a comparison of the results obtained from the program with those from two previous studies, the performance of the developed FEM program was validated. To apply this program to real dredging fields, two data sets obtained from sedimentation tests for Korean marine clay were analyzed.