## 3 Installation Methods and Circuit Protection
### Circuit Protection  
Traditional installation methods are mostly on-site installation methods, which come with problems such as increased time consumption, low work efficiency, serious interference with normal construction operations, and a lack of conductivity with large-scale monitoring. Specifically, the subsequent operations of blasting and drilling concrete posed  
Figure 16: Field installation and data logging. (**a**) Installation of steel arches; (**b**) flange connection; (**c**) line protection; (**d**) data logging.  
Figure 17: Peg welding. (**a**) Welding hook; (**b**) steel pipe + reflective strip protection.  
additional challenges that impacted the installation time. In addition, the on-site working space was small, and the above problems could therefore not be effectively solved by increasing manpower. Through field practice, it was found that the time required for sensor installation and wiring was about 2 h. In addition, the site geological conditions were harsh, the construction environment was complex and changeable, and issues with the line were frequent. The main types of line damage were blasting damage, man-made damage, and mechanical damage, as shown in Figure 18. Damage to the line directly led to the instability of data transmission, which seriously affected monitoring quality and continuity. However, the reliable transmission of data could be ensured via effective protection of the line. The existing installation method was not suitable for the construction of soft rock tunnels under high stress and high water conditions. In accordance with the relevant field processes and geological conditions, the author put forward a new line protection method.  
For protection of the junction box, due to its extremely light weight, a distribution box was used. However, sometimes, an explosion occurred during the blasting process. Therefore, a 5 mm thick steel plate was used and welded to a 50 \(\times\) 50 \(\times\) 50 cm steel box, which was suspended and welded to a height, as shown in Figure 19.  
The wearable wire hose (Figure 20b) was used to protect the communication cable, but the protective effect was still not particularly strong, and blasting failures and excavator damage often occurred. Thus, further protection, using a galvanized steel pipe and a reflective strip (Figure 20c), was introduced. This protection method had good effectiveness and prevented damage from blasting and stone crushing. Moreover, the reflective strip provided a good reflection effect. In addition, these protective factors prevented excavators from tearing the wire during slag removal operations.  
Figure 19: Protection of junction box. (**a**) Junction box failure; (**b**) distribution box; (**c**) steel box.  
Figure 18: Line damage. (**a**) Man-made damage; (**b**) blasting damage; (**c**) mechanical damage.  
In order to avoid crushing caused by high ground stress, the lead wire was pre-punched using a PPR tube (Figure 21b), and the U-shaped cable was inserted into the bottom of the PVC tube to protect the displacement meter line. However, the tube presented strong bending resistance, insufficient flexibility, and unsatisfactory results. In the later stages, a flexible PE hollow tube was used to avoid the bending of the optical fiber line, which produced good results (Figure 21c).