Relying on the foundation engineering of the main tower caisson of Changtai Yangtze River Bridge

the variation of the soil pressure under the cutting edges of the caisson is modeled in the initial sinking stage by finite element method(FEM). In combination of the field measurements of the soil pressure

the variation trend of the soil pressure is analyzed along the cutting edges of the caisson during the excavation steps. The study shows that the numerical results are in agreement with the field measured soil pressures. The soil pressure will decrease in the region where the soil is excavated in caisson cells. It decreases more obviously while the excavation becomes deeper

and the soil pressure will increase in the cutting edges of the neighbouring caisson cells. In the process of excavation from internal caisson cells to outer ones

the soil pressure of the cutting edges of the outer bulkhead and skin of caisson accumulates. Finally

the soil reaches the bearing capacity and it develops into plastic state. The caisson sinks obviously. The work performed in the paper helps guide the smooth sinking of the similar caisson.