Abstract: Frost heave consists of in-situ heave, discontinuous ice lens and final ice lens.Thickness of final ice lens is the key factor influencing on frost heave.In order to study on the characteristics of final ice lens at different overburden pressures, the tests using saturated Lanzhou silty clay and Lanzhou clay were carried out.The evolution of final ice lens was analyzed by using visual equipment and the binarization method of images during the freezing process of saturated samples.The results indicated that the thickness of final ice lens decreased with the increase of overburden pressure for the same soil types, and the thickness of final ice lens in saturated Lanzhou silty clay is larger than that in Lanzhou clay at the same overburden pressure.Equivalent water pressure and hydraulic conductivity are the key factors to the segregation rate of final ice lens when regarding lens growth as a quasi-static process and using the thermodynamic theory for the liquid layer near a substratum.At last, the fitting functions between average segregation rate and overburden pressure are acquired.