Digital image processing technique is used to study the Duncan-Chang model parameters based on the triaxial tests. The research has recorded valuable data using the newly developed measurement method. There are great differences between the Duncan-Chang model parameters conducted from the digital image processing technique and traditional measurement methods. The reasons that cause by the different measurement technique and measurement area are analyzed. The influence degree of parameters variety on displacements results is discussed through numerical analysis. As a result of our experiments

we conclud that the parameters K and Kb from digital image processing technique are two to three times higher than the values from traditional method. Furthermore

the displacements are about half of the value calculated from the traditional method.