Experimental study on damage evolution characteristics of segment structure of shield tunnel with cracks based on acoustic emission information

Cracks are constantly observed in segments due to adverse geological conditions and loads during shield construction. However, crack propagation can have a negative impact on the stress deformation of the segment structures in the long run. Revealing the characteristics of energy release during crack propagation can effectively reflect the damage evolution process. Based on an investigation of segment cracks in a subway tunnel project, this paper conducts an in-depth analysis of AE data of segments through similar model tests, and explores the influence of cracks of different lengths, quantities and positions on the damage evolution of segments of shield tunnels. The results show that cracks reduce the overall stiffness of the structure when compared with that of a segment ring with no prepared cracks, and the elastic bearing range increases slightly, while the plastic bearing range decreases obviously. With the increase of the length and number of prepared cracks, the number of ladders of AE events decreases and the height of ladders increases, and the number of AE events of segments increases continuously at the critical point of instability. The damage of segments appears earlier, and the development process of the damage and is relatively gentle if cracks are located at the arch waist. By contrast, the damage of segments is more serious if cracks are located at the arch roof and arch bottom. The results provide theoretical basis for design optimization, disease analysis and evaluation of shield tunnel.