Three-dimensional swelling of clay lumps

The disposal of large volumes of clay lumps obtained from underground construction activities and seabed dredging is a problem in a highly built-up environment such as Singapore. The use of such clay lumps for reclamation of land is an environment-friendly proposition. The clay lumps, when placed under water, will undergo three-dimensional swelling. Calculation of the degree of swelling is important for making decisions on when to place surcharge, and in what quantity, on top of the fill for closing the inter-lump voids. This paper reports the results of experimental and numerical studies that were carried out to understand the swelling behaviour of clay lumps when placed under water. Experimental results were compared with finite element method results using linear and non-linear elastic models. The study shows that the suction present in the lumps increases initially, before dissipation, suggesting the presence of the Cryer-Mandel effect during three-dimensional swelling. The importance of simulating continuous changes in soil modulus and permeability for realistic simulation of three-dimensional swelling of clay lump is reported. The influence of lateral restraint on the swelling behaviour is also analysed.