In order to study the expansive soils deformation over time，carries out two groups of experiments on Nanning expansive soils，which one is indoor 1-D immersion test and the other is foundation irrigation simulation. After a long period investigation on the time-related swelling ratio and the expansive soils deformation around pile base， founds that though soil samples containing different initial moisture and dry densities，the loaded expansive soils appear similar deformation behavior over time. When loaded（>50 kPa），the curve of swelling ratio lg against time can be generally divided into three stages，which can be accurately described by exponential law in semi-logarithmic coordinates, and for unloaded samples，the relation of lg ~t can be more precisely fitting with logarithmic function. Then conducts a numerical simulation to analyze the model pile test，establishes an exponential function relation concerning the time-related swelling behavior of the pile side soil, and lays experimental basis for further exploration on interactions between piles and expansive soils.