Abstract：Based on understanding the reason of ground surface deformations resulting from the construction of shield tunnel，the effects of the shield tail void，the degree of filling grout and the disturbance of soil around the tunnel on the ground deformations are generalized as an equivalent circle zone，and the degree of sensitivity of the surface deformation to its parameters is also discussed. With the measured data，the parameters of equivalent circle zone can be obtained by back analysis of soil displacement. The case study shows that the proposed method is reasonable and satisfying in actual engineering.
