Abstract: In this paper, based on the engineering background of the intensive monitoring of the Wuhan metro line 4 cross-river tunnel during the flood season in 2020, the project analyzes the ring-by-ring monitoring data of the entire section of the cross-river tunnel by applying the ring-by-ring monitoring data measured by the three dimensional laser shield structure and determines the key monitoring intervals. Three round-by-ring encrypted monitoring data discussions in key monitoring intervals illustrate the trend of convergence changes caused by the continuous rise of the water level of the Yangtze River. Combined with the distribution of manual monitoring points and data characteristics, it shows that there are many blind areas in traditional manual monitoring. When we focus on absolute position changes, which makes the tunnel structure relative changes in morphology to be ignored. The cross-river tunnel is located in a complex geographical and geological environment, and the three dimensional laser ring-by-ring monitoring in flood season provides an effective guarantee for the safe operation of the tunnel.

Key words: three dimensional laser, ring-by-ring inspection, tunnel structure form, safe operation