Modified Cambridge model has been widely applied to geotechnical engineering; and it is important to decide the values of parameters in this model. One of the efficient ways to obtain these values is the back analysis based on the measured displacement. The finite element method is used to calculate the horizontal displacement at the front of the pier improved with drilled grouting piles. The changes of the displacement at that point with each parameter are analyzed. The results show that the four primary parameters are the dimensionless parameter related to elastic modulus
the exponent related to elastic modulus
Poisson’s ratio and the test constant of the virgin curve of isotropic loading
which have great effects on the displacement. This result may provide the basis for choosing the parameters for back analysis