Abstract： Due to the influence of adjacent construction work, the cumulative deformation of shield tunnels continues to develop and which brings the occurrence or aggravation of shield tunnel disease, such as cracks, breakage, leakage, staggered platform, joint opening and disengagement of ballast bed. Based on the measured data of a large number of shield tunnels in soft clay, the state of the shield tunnel in the soft clay stratum is generally in poor condition, and the proportion of the horizontally convergent deformation greater than 5‰D (tunnel diameter) is as high as 75%, and the structural diseases (cracks of segments, leakage, dislocation of ballast bed, staggered platform inside the pipe ring, opening of the longitudinal joint) are serious. According to the statistical data, the relationship between horizontal convergence deformation and structural diseases was respectively established. With the increase of horizontal convergence deformation, the upper limit of the maximum crack width, the number of cracks, the maximum amount of disengagement of ballast bed, and the maximum amount of staggered platform inside the pipe ring increases linearly, and also the maximum crack depth increases slowly. At the same time, the proportion of diseased pipe ring also rises with the increase of horizontal convergence deformation. When the horizontal convergence deformation is small, fewer diseases occur. As the horizontal convergence deformation continues to increase, the proportion of serious structural diseases such as crack width greater than 0.4 mm, leakage of sediment, dislocation of ballast bed greater than 4 mm and staggered platform inside the pipe ring greater than 4 mm increases. It is recommended to use the probability of 2% as the horizontal convergence deformation control limit value. That is, controlled by the 0.2mm crack width, the 4mm disengagement of ballast bed, the 4mm staggered platform inside the pipe ring and only-longitudinal-seam wet, the horizontal convergence deformation limit is 20mm. And controlled by the 0.4mm crack width and the 6mm disengagement of ballast bed, the horizontal convergence deformation limit is 50mm.
