One-dimensional consolidation of lumpy clay with non-linear properties

Abstract

When dredged clay lumps are used as reclamation fill, large voids exist between the lumps. Thus consolidation of the lumps themselves, and closing up of inter-lump voids, contribute to the overall settlement, making the fill a complicated non-linear medium. Yang et al. (2002, Géotechnique 52, No. 10, 713-725) have used the double porosity model to describe the consolidation of this type of fill using linear properties to arrive at analytical solutions. In reality, the behaviour is highly non-linear, and the finite element (FE) method is used to solve the non-linear equations. Results from the FE analysis of the consolidation of the lumpy clay fill were shown to be able to match the analytical solutions. Two one-dimensional consolidation tests were conducted for this study. In the first case, water was used to fill the inter-lump voids, whereas in the second case, slurry was used. The procedure for determining the permeability and the e-logσ' relationships for the inter-lump and intra-lump systems is explained in this paper. All the parameters could be estimated from various tests, except for the fluid transfer parameter, and this was back-analysed, using data from other works as a guide. The results presented show that the model can predict well the measured settlement and pore pressures in inter-lump and intra-lump systems in both experiments, essentially because this is a back-analysis. But the fact that the model can provide consistent prediction of numerous parameters indicates that the model is able to capture the essence of the mechanics of a lumpy clay system.