Excavation and Lateral Supports design in Plaxis

Question

Permanent bored piles are used as retaining wall and permanent foundation in my ELS design. 
 I want to consider the "at rest / long term condition" of the soil after the ELS work is completed (i.e. K0 condition in my final stage of the model), may I know how to define K0 condition in my final stage?

Stefanos Papavasileiou · Answer

Dear Kwai Yuen Lai, 
 In the long term a stress state indeed slowly returns to K0NC condition (not that this is not the K0 condition) and this can be assumed to be an effect of creep and stress relaxation. Hence, the only way to do it is by using the Soft Soil Creep model and allow a very long time for the analysis to reach that the K0NC stress state. 
 Alternatively, if the focus of the analysis is not to predict accurate settlements, it is possible to make a copy of the current project and edit the InitialPhase to be equivalent to the last phase of the reference model. This means that InitialPhase will be at the same state as the reference project. Then, perform a Gravity Loading to get initial equilibrium stresses according to the geometry layout of end-of-construction and continue from that state. Note that this alternative ignores any behaviour due to overconsolidation, which means that if the reference project has overconsolidated materials this way of modelling does not apply. In that case, only the approach with the Soft Soil Creep model can be used. 
 Keep in mind that choosing a methodology is based on engineering judgement and where the focus of the analysis is. For instance, retrieving a safety factor will be accurate after a long term creep condition is applied, while settlements are highly influenced by the creep parameters, so attention is required.