Prediction of Consolidation of Very Soft Soil

Abstract

An alternative method of calculating one‐dimensional primary consolidation of fine‐grained material is presented. The procedure is based on solution charts developed from a finite difference computer solution of the dimensionless governing equation of finite strain consolidation theory. The solution charts are plots of percentage consolidation versus a dimensionless time factor for initial and boundary conditions corresponding to normally consolidated and underconsolidated (zero initial effective stress) materials subject to single or double drainage and can be used similar to the conventional plot developed from the dimensionless solution of the Terzaghi consolidation equation. The chief advantages of the method are that finite strains are allowed, and the non‐linearity of soil properties is considered. The methodology is well suited to the calculation of consolidation settlements in very soft fine‐grained materials such as dredged fill hydraulically placed in confined disposal areas. A technique for handling the case of multiple consolidating loads (the periodic deposition of new material or placement of subsequent surcharges on previously placed and partially consolidated layers) is also proposed. Practical applications of the methodology are illustrated by calculation of settlements in two dredged fill disposal areas in which settlements were measured.