Based on one-dimensional consolidation-creep tests

comprehensively considering primary consolidation and creep effects

the one-dimensional Koppejan model was selected to characterize the time-dependent deformation of soft soils

and the model was extended to the three-dimensional stress space in incremental form

and the corresponding material subroutine was implemented in ABAQUS software. The subroutine was then applied to a numerical analysis considering pile-soil coupled interactions based on a field prototype test. The time-dependent variations of pile response

additional pressure acting on the pile shaft

and the soil-arching between piles under long-term surcharge loads were investigated

and the mechanism of time-dependent interaction between passive piles and soft soils was revealed. Results show that the additional load caused by the surcharge load is mainly distributed in the relatively soft-weak layer

and increases with increasing duration of loading

but its distribution range is unchanged. With increasing duration of loading

the soil plastic zone between the passive piles enlarges

the arch height of principal-stress decreases

and the soil-arching effect continues to weaken. The weakening law of the soil-arching effect changes with the change of surcharge conditions. The smaller the surcharge distance or the greater the surcharge load is

the longer the time for the pile response reach a steady growth stage

and the more significant the time-dependent influence of soft soil deformation on pile response is. For different thicknesses of soft soils

the distribution range of the additional load acting on the pile shaft is different

resulting in different influences of the surcharge load or the loading duration on the pile response distribution. The deduced extended Koppejan model well reflects the process of time-dependent interaction between the pile foundation and soft soils and provides reference for the prediction of the long-term lateral deformation of pile foundations.