^Title Wireless Monitoring of Anchor Loads

The challenge is for the new station and tunnel to be built without interrupting services at Zürich Hauptbahnhof, which has 340,000 daily passengers and at least 2,900 train services a day

Working with the geotechnical company, Mantracourt’s innovative T24 radio telemetry devices were used to wirelessly monitor the forces exerted upon cable anchors which are holding back concrete retaining walls within a construction pit. The pit was the start and end point of the tunnel boring machine digging the 5km tunnel and was eventually 16 metres in depth.

Ground anchor heads, fitted with specialist PRE electrical loadcells, measured forces of between 400-700kN pulling on anchor cables. Due to the exposed environment within the pit, Mantracourt’s wireless sensing module T24-ACM with strain gauge input unit was located close to the anchor head. The T24-ACM has a IP65 protective case with powering to the acquisition module via 2 DCell batteries. The low power requirements of the acquisition modules mean that data can be provided well beyond the shelf life of the batteries, e.g. over five years. Data is transmitted on license-free 2.4GHz frequency from the acquisition modules to a T24-BSi industrial base station located 50 metres away at an access point which has mains power and Internet connection. Here the industrial base station acts as the receiver and is linked to a PC via RS485 cabling. By logging the data to a log file, the monitoring firm could access this data remotely via the Internet, gathering live data from an entirely remote location across the city.

Should it be required, a T24-HS handheld display could be used by personnel visiting the construction pit to gain readings from each of the acquisition units positioned within the pit.