Effect of spatial variability on short- and long-term behaviour of axially-loaded cement-admixed marine clay column

This paper examines the usefulness and challenges in using an advanced effective stress constitutive model in random finite element study on the effect of spatial variability on global behaviours of axially-loaded cement-treated clay column. The main challenge lies in the large number of parameters which need to be simplified and the amount of data needed to facilitate model randomization. To enable selection of parameters to be properly simplified, a sensitivity study was conducted which indicates that the main behavioural aspect requiring randomization is the size of the initial yield locus, which is closely related to the mix ratio. Other parameters are shown to have lesser impact on the behaviour. The results show that, under undrained condition, the strain-softening nature of the model leads to lower strength and higher strength variability than the Tresca model. The use of an effective stress model allows the long-term behaviour. Since the material is strain-hardening under drained condition, deformation is likely to be a limiting factor on column loading in the long-term. The important parameters are likely to be the drained working modulus and yield stress. Where long-term settlement is a key performance index, long-term stress level may need to be kept within the elastic regime to avoid excessive long-term settlement.