LAUSR

Abstract Capturing the cracking process during prototype loading tests of segmental lining is crucial for the design of tunnel structures. This paper presents an application case history of 3D digital image correlation technique to monitor the cracking behaviour of concrete lining during prototype loading tests of a special-shape tunnel. The principles based on the displacement field to identify cracks, to determine the onset of cracking and to calculate the crack width were defined. The cracking behaviour at the three measurement regions was discussed. In particular, three distinct cracking stages corresponding to different deformation statuses were identified including a primary deformation stage with small deformation, a steady-state cracking stage with a constant cracking rate and an accelerating cracking stage with an increasing cracking rate. The bearing capacity of segment structures corresponding to the crack width prescribed by the Chinese design code was obtained. This study has shed light on the application of non-contacting optical techniques to capture the deformation characteristics of concrete structures in the full-scale experiments as well as civil engineering practice.