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

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.