Abstract: Expansive soil stone remoulded samples from the base of an expressway were taken for opening and non-opening expansive soil water immersion expansion test and large-scale expansive soil samples with different thicknesses were taken for water immersion expansive deformation test in order to study the influence of different modes of water injections on the expansion increment of expansive soil and the change rule of immersion expansion of large-scale remoulded expansive soil. The test results show that the expansion time interval curve of the expansive soil injected with water through opening and non-opening way is largely different. To be specific, the expansion time interval curve of the soil sample injected with water through opening way can be generally divided into three stages: initial fast expansion stage, decelerated expansion stage and stable expansion stage; on contrast, the expansion time interval curve of the other one through non-opening way can be divided into four stages: initial slow expansion stage, fast expansion stage, decelerated expansion stage and stable expansion stage. The relationship between soil sample loss volume fraction and expansion increment loss is analyzed to be Δδ=0.617ΔV+0.02. The expansion time interval curve of the large-scale expansive soil sample with different thicknesses is in a convex growth trend, so is the expansion increment after the water injection of each grade. The real expansion increment of the large-scale expansive soil sample will increase along with the increase of thickness but the amplitude of increase declines. The real expansion increment will decline along with the increase of overlying load, but the amplitude of increase declines.