Lining crack evolution of an operational tunnel influenced by slope instability

Abstract

Integrity is a common measure of the health of a tunnel. However, the relationship between integrity and developing anomalies is still unclear. Thus, this study acquires comprehensive recordings of lining cracks of a tunnel to enhance our understanding of tunnel degradation and lining crack evolution. Detailed anomaly variation of a deforming mountain tunnel that is influenced by slope movement were obtained from 2008 to 2015 utilizing high resolution images of lining surface. During the recording, the length of cracks within monitoring section increased at a rate of 54.46–86.85m per 180days. New cracks appeared within the recording period emerged mostly at the same locations as the existing cracks found in the beginning of the recording, suggesting that crack development is highly relate to the location in the tunnel. The evolution of cracks also varies with the preexisting crack patterns. Lining crack patterns that stretched over different construction units, which implies the effect of regionally or overwhelmingly external factors to tunnel degradation, can be characterized as transverse cracks, closed cracks and inclined cracks. Cracks with similar patterns evolve similarly in their lengths, densities and spalling area, except for transverse cracks at deep overburden. For advances in life cycle base tunnel maintenance, a tunnel in operation should be divided into zones based on the patterns of existing lining cracks or environmental boundaries at the beginning of monitoring. Subsequent interpretation can be performed to verify and modify tunnel zoning, revealing representative properties of the evolution of the cracks with a view to identifying integrity criteria and methods of repair.