For lining segments of shield tunnel under the same loading conditions, the position of key block may significantly affect the

mechanical response and failure characteristic of lining structure. The progressive damage theory was firstly introduced into the

disease occurrence and propagation analysis of shield tunnel segments, and a comparative study was carried out based on the similarity

model test for the influence of different position of key block during the whole progressive failure process of lining segments. The

acoustic emission data, displacement and internal force of lining segments as well as the crack occurrence and propagation in lining

segments were analyzed comprehensively. Consequently, the results show that: 1）The difference in position of key block may lead to the

difference in position of hoop joint. Under the same external load, the coordinated deformations between the segments and the strata may

be different so that the integral stiffness of the entire ring could be different. The integral stiffness for the case with key block

located at haunch is larger than the other two cases. 2）The difference in position of key block may significantly affect  the position

of the maximum local deformation. The ratios of the maximum displacement to the tunnel radiusat the critical buckling point do not

change remarkably, and in fact, the range generally varies between 2% and 3%. 3）The difference in position of key block may also have

significant influence on the load levels at the occurrence of macro cracks as well as the locations of macro cracks. For the case with

key block located at the haunch, the load level at the occurrence of macro cracks is larger than those for the other two cases, with

much more major cracks and crushing zones.