Characterizing crack patterns on tunnel linings associated with shear deformation induced by instability of neighboring slopes

Structural safety inspections of operational tunnels are conducted to detect lining anomalies as early as possible and to repair menacing anomalies in time. Understanding the causes of a lining anomaly is essential to implementing the correct right countermeasures to repair an anomaly. However, many factors affect the structural stability of tunnels, possibly resulting in a wide range of lining anomalies. Identifying the possible causes based on inspection results is an important task for maintaining the safety of operational tunnels. This work focuses on a common lining anomaly, cracks, caused by neighboring slope movement. By systematically characterizing the spatial distributions, textures and appearances of cracks on a tunnel lining surface, possible causes of lining anomalies can be identified. Additionally, the degree of tunnel cross-sectional deformation and associated slope movement can be estimated. This work applies a novel approach to identify the possible causes of specific crack patterns on a tunnel lining surface resulting from neighboring slope instability. Four cases with lining surface images, layouts of identified anomalies, and 3D spatial distributions of anomalies are provided for illustration on possible causes interpreting and/or identifying. Moreover, data needed to recognize patterns in lining cracks are reviewed. Some suggestions for tunnel structural safety inspections and associated techniques are also given.

Research highlights
► Movement of a slope neighboring a tunnel causes various cracks on its lining.
► Slope movement perpendicular to tunnel axis induces longitudinal cracks.
► Slope movement parallel to tunnel axis induces transversely circumferential cracks.
► Slope movement oblique to tunnel axis induces inclined circumferential cracks.