Study on the failure pattern of shield tunnel segments damaged by perforation under surcharge loading

The penetration of prefabricated piles into the underlying shield tunnel segments during construction frequently occurs and poses significant hazards. Occasional surcharge loads, such as large pile drivers and piles piled up on site, can further exacerbate the failure and damage of the penetrated segments. This paper employed a 1∶8 scale model test method to investigate the failure patterns of shield tunnel segments damaged by penetration under surcharge loads, considering factors such as the size and location of the segment penetrations and the form of surcharge loads. The research results indicate that when the diameter-to-width ratio is small, the load required for segment failure decreases significantly, exhibiting an overall marginal decreasing trend. Changes in the location of penetrations can alter the stress distribution, thereby affecting the direction of segment through-cracks and the magnitude of segment failure load. Using the diameter of the penetration and the length of the crack as hazard evaluation indicators, it is found that the damage caused by penetrations to segments is much greater than that caused by longitudinal cracks, which in turn are much more harmful than circumferential cracks.