Post-construction monitoring and analysis for highway tunnel lining cracks

Lots of lining cracks have been found when a highway tunnel is open to traffic for only a short period of time. Investigation of the cracks was conducted to obtain the statistics, which includes the number, length, inclination, width, and depth of typical cracks. The causes for cracks occurrence were analyzed using the geological observation report during construction, construction recording, monitoring data, field investigation, and numerical analysis. Such factors as the geology, construction, uneven load and design were considered as the major causes of cracking. Concrete shrinkage and the 5.12 earthquake were also believed to have influenced the crack appearance. Some typical cracks were selected for monitoring the three-dimensional extension, depth development, length growth and increase of the cracks. Through analysis of the collected data, the load-bearing condition and safety of the tunnel lining were diagnosed and evaluated. It was believed that the tunnel lining was stable and safe, even with the cracks. Suggestions for crack treatment were presented.