Measurand’s SAAF can be used to monitor convergence in a section of tunnel. When monitoring convergence, the SAAF is pulled into 27 mm (1.063") internal diameter (ID) conduit and then attached in a circular arc in the tunnel cross section. When selecting an SAAF for convergence monitoring, it is important to choose an appropriate segment length. The appropriate segment length is determined by the radius of the tunnel cross section to be monitored:

  • 500 mm segments for tunnels with radius of 3.5 m or greater
  • 305 mm segments for tunnels with radius of 2.0 m or greater

WARNING: In some cases, tunnels are considered to be explosive atmosphere (ATEX) environments. Certain ShapeArray products are certified for use with EX ’d’ Flameproof protection in areas classified as Zone 1 or Zone 2 in accordance with European Directive 94/9/EC when installed in compliance with the ATEX Workplace Directive 1999/92/EC. Existing certification is only valid in Europe. Exact requirements for proper usage should be discussed with Measurand, all certification authorities, and the end user before ShapeArray is installed in any hazardous location.

Step 1 - Position the SAAF Reel

Place the reel such that the SAAF will feed off the bottom of the reel. Ensure you position the reel such that there is enough space to lay out PVC conduit equal to the length of the SAAF.

Step 2 - Assemble PVC conduit

Clean and deburr the PVC conduit. Lay out and align the sections of conduit with the SAAF reel with a small gap (approximately 10 cm) between each section. Ensure that the bell ends of the conduit are all facing towards the reel. Pull a rope through each section of conduit. Assemble and glue each section of conduit using PVC cement.

Figure 1: Position reel with SAAF coming off bottom and lay out conduit with bell ends facing reel

NOTE: In cold temperatures, it is imperative to use a cement rated for the expected temperature. Ensure you follow the PVC cement manufacturer's instructions when using these products. Most manufacturers specify applying glue to only one surface of the joint. Use tape to secure glued joints during curing.

Step 3 - Pull the SAAF into the Conduit

Attach the rope that was pulled into the conduit to the eye bolt at the tip end of the SAAF. Use the rope to pull the SAAF into the conduit until one or two segments are through the end of the conduit.

NOTE: This will process will require multiple people. Someone will need to guide the SAAF into the conduit. Also, as the SAAF is pulled into the conduit, friction will build up making it more difficult to pull. Several people may be required to pull the SAAF.

Figure 2: After the conduit has been glued together, pull SAAF into it with rope

Step 4 - Add PVC End Cap and SAAF Install Kit

Add an appropriate length of PVC over the end of the SAAF sticking out of the conduit and attach an end cap. Attach the bottom half of top stack assembly from the included install kit to the PVC at the cable end of the SAAF and tighten the set screws. Cut away excess PEX tubing and thread the top portion of the top stack onto the cabling and screw it to the bottom portion. Tighten the cable gland on the top stack to prevent moisture from entering the SAA+PVC assembly.

Figure 3: Seal the conduit using an end cap and the SAAF Install Kit

Step 5 - Attach the SAA+PVC Assembly to the Circumference of the Tunnel

A support mechanism that offers at least two points of support must be used for installation. A minimum bend radius of 3.5 m (11.5’) for 500 mm segments and 2 m (6.6’) for 305 mm segments must be maintained. Scaffolding is a good support mechanism; however, anything that can provide at least two points of support can be used.

Figure 4: Attach the SAA+PVC to the circumference of the tunnel while ensuring to properly support it

Attach the SAA+PVC assembly to the circumference of the tunnel, as shown in the figure above. Measurand recommends using conduit routing clamps, such as U-clamps, every 2 m - 3 m (6.5’ - 10’) for attaching the assembly. For 27 mm (1") Schedule 40 PVC conduit, a U-clamp with an ID of 33 mm (1 and 5/16") should be used.

Figure 5: An example of a U-clamp for securing the SAA+PVC assembly

Once the SAA+PVC assembly has been completely attached to the tunnel, the communication cabling can be run to the data acquisition system.