## 5 Site Experiment Results
### Tunnel Monitoring Scheme  
The longitudinal arrangement of sensors of the WSN monitoring system is shown in Figure 9. To monitor the tunnel deformation during construction in a shallow buried region, four WTDS nodes were deployed, three of which monitored the deformation of a transverse section near the tunnel face, and one sensor monitored the face deformation. The sensor locations in the transverse section were based on the arrangement in Figure 1a. The sensor for monitoring the tunnel face deformation was based on the configuration in Figure 1b. Based on the layout of the three sensors in monitoring Section 1, the horizontal convergence is measured by one of the sensors. The other two sensors were pointed towards a reflection target at the tunnel crown of this transverse section to obtain the settlement deformation. To facilitate installation and maintenance of the sensors, they were installed at about 2 m above the excavated invert so that the site engineers could notice the sensors without accidental contact. When the CD method was used for construction, the three sensors were installed on the same side of the tunnel lining according to the on-site construction conditions. Figure 8: The geological layout of the Tongluoshan mountain at the shallowly buried tunnel region. Monitoring Section 2 was implemented to monitor the deformation of the tunnel face. The installation and layout position of the sensor in Section 2 needed to be adjusted according to the site conditions. In principle, it should be as close to monitoring Section 1 as possible and should not be more than 30 m away from the tunnel face. If conditions permit, it should be arranged at the upper half of the transverse section to ensure that the front interference does not affect the laser sensor. When the distance between the excavation tunnel face and monitoring Section 1 exceeds 20 m, it is necessary to arrange on-site personnel for dynamic installation and layout. The basic installation and layout method is to move the monitoring sensors of Section 1 forward to about 10 m from the face and move the sensor in Section 2 accordingly. Since the tunnel face of the monitoring region is about 500 m away from the tunnel entrance, a relay device was implemented at the midpoint between the tunnel face and the entrance (about 250 m away from the tunnel entrance), which could transmit the monitoring data to the gateway. A gateway was installed at the entrance to send the data to the cloud server. The monitoring time started on 2 March 2022 and lasted for three weeks until the tunnel excavation passed beyond the shallow buried region and stopped on 24 March 2022. The monitoring data were set to record once every 5 min. Based on the monitoring data in Section 1, the tilt and distance of the two sensors pointing towards the tunnel crown can be obtained. The settlement over the three weeks can be obtained using the data filtering method introduced, as shown in Figure 9(a). The horizontal convergence of the transverse section can be similarly obtained (Figure 9(b)). It should be noted that the crown settlement presented in Figure 9 has eliminated the significant movement of the sensors. The horizontal convergence has eliminated the outlier values due to the blockage of the laser beam caused by construction equipment, slagging, and site personnel. Based on the monitoring data in Section 2, the tunnel face deformations are computed and plotted in Figure 9(c). Due to the dynamic construction process, the tunnel face distance from monitoring Section 2 changes over different construction cycles. The obtained monitoring data are filtered to reflect the actual movement of the tunnel face in each construction cycle and eliminate the extended distances caused by the excavation. As shown in Figure 9, the filtered monitoring data of crown settlement and horizontal convergence agree well with the total station measurements. They can reflect the dynamic changing of deformations during tunnel construction.