Digging deeper with monitoring

Author: Martin Rub, Lidija Špiranec & Katja Omlor

Swiss Federal Railways (SBB) initiated a long-term expansion project together with the city of Winterthur to increase the performance of the Winterthur railway station. Due to the increasing number of passengers deciding to go with this environmentally-friendly transport alternative – daily around 120.000 people – Switzerland’s fourth-largest railway station required a larger pedestrian underpass in the North for better entrances to the platforms, as well as an adjacent bicycle tunnel which connects the two parts of the city and is also leading to a large bicycle garage. The planned new pedestrian and bicycle underpass also included various stores for an enhanced shopping experience. For this complex project – especially when stopping the rail traffic was not an option –  the SBB contracted ARGE STRABurg (STRABAG AG and Burger Stahlbau AG) for the construction part, whereas Terradata AG was chosen by the Contractor for the entire monitoring and surveying scope of the project.

The expansion has a functional and visual undertone: asides to raising the quality of travelling and living, this project is supposed to help turn the Winterthur train station into an attractive city gate entrance, connecting the old town centre and the new part of the city. The new pedestrian and bicycle underpass, a new logistic centre and an underground parking spot for cyclists will increase passengers’ safety and comfort when choosing this type of transport.

Whenever a project touches people’s lives, especially in terms of their safety, selecting the best partners is of utmost importance.

A daring project with high safety requirements

The new pedestrian underpass “Nord” at the Winterthur railway station passes under seven existing railway tracks. For this purpose the engineering consortium, encompassing Locher Ingenieure AG, F. Preisig AG and 10:8 Architekten GmbH, created a concept of a 50-metre wide corridor - with 14 temporary railway bridges overpassing it during the four years of construction. Moreover, to safely guide the pedestrians during the duration of the project, PUWI engineering consortium planned a separate temporary steel bridge for the pedestrians. This temporary bridge needs to be monitored for safety reasons, too. Finally, this complex project also encompasses an existing car park above the train station, including an access ramp. The parking deck will be statically laying on top of the train station. In the underpassing area, the pillars have to temporarily support the construction of the new underpass ceiling and the pre-mentioned pillars for the parking deck.

Figure 1: Cross-section of the new underpass and the temporarily supporting micropiles for the parking deck framework above. The visualisation also shows the parking deck and the temporary bridge (left and right) including anchors. The coloured points emphasise the monitored points. Drawing by Locher Ingenieure AG.

During the construction, settlement and displacements of the operating tracks, the temporary bridges and the existing parking deck, overlaying the train station, have to be permanently monitored every 15 minutes.

As the railway needs to remain fully operational and safe, the monitoring system Terradata installed sends alerts as soon as it detects movements outside of the defined thresholds. This complex project combines not only measuring track deformation but also monitoring other building processes during the complete overhaul of the parking deck. For these reasons, the temporary bridges are monitored by magnetic reflective prisms at every end (blue points). In front and behind the temporary bridges, the rail tracks are monitored every 4.8 m (blue points). The temporary pillars, supporting the parking deck (magenta points), are monitored on four different height levels to detect possible settlements while excavating their micropiles.

Figure 2: Terradata’s concept for measuring all the coloured monitoring points. Drawing by Locher Ingenieure AG.

The monitored area has to be expanded to neighbouring buildings too to prevent structural damage and ensure peoples’ safety. Terradata AG collects data using geodetic and geotechnical monitoring sensors. Based on the gathered data, 3D deformations are calculated (like twist and settlement of railways tracks and other typical railroad parameters).

Figure 3: Leica Geosystems monitoring total station on a ceiling mounting plate.

Figure 4: Left: A train passes the temporary bridges, supported by micropiles. Right: The transition zone of the track ballasts onto the temporary steel bridges. Both structures are measured by Leica total stations every 15 minutes over three years.

The monitoring super package

Terradata relies on Leica Geosystems’ total stations and its GeoMoS monitoring solution for automatic deformation monitoring, one of the crucial parts being the Leica Nova TM50 monitoring total station. It is the best instrument for monitoring railway operation – fast and quiet, barely ever getting noticed by the passengers on the platforms.

The equipment combination, chosen for the Winterthur site, was:

• 7 Leica Geosystems automated monitoring total stations
• 420 glass precise reflective prisms
• 25 hydrostatic levels for building subsidence monitoring
• 20 pressure sensors to monitor load
• 2 vibration sensors to monitor structural vibration
• 40 crack meters to monitor the impact of underpinning the railway building
• 20 tilt sensors to monitor micropiles

Figure 5: Left: BIM model of the underpinning construction of the railway building with its micropiles. Right: Excavation work where the building was pressed onto the temporary micropiles (BIM by F. Preisig AG).

Figure 6: TEDAMOS (Swiss Monitoring Solution by Terradata) Web Viewer with all measurements for the underpinning of the railway building. Two 3D Leica total stations monitored the façade. A water levelling system monitored the height of the existing building, and the expanding way of the 40 hydraulic presses was measured by crack meters. Biaxial MEMS sensors monitored the inclination of the micropiles. The monitoring project was continuous (24/7) with a measuring interval of up to 1 minute while activating the load presses.

Figure 7: Example of the deformation time series of one parking deck monitoring point, showing seasonal effects (expanding and shrinking) of the steel structure (dL component) and the alarm levels in yellow, orange and red.

Figure 8: Leica Geosystems monitoring total station on a slanted pillar.

Choosing the right partner

Terradata AG, Switzerland’s largest provider of surveying and monitoring services, took on this exciting monitoring challenge.

“Our solutions aim at early detection and defence against potential dangers – we are specialised in ensuring safety where structures, infrastructures, soil and natural hazards play the main role,” said Martin Rub, Teamleader Monitoring. “The railway project in Winterthur allows us to apply our entire set of equipment and software. We’ve chosen Leica Geosystems’ monitoring solution because we always strive to keep our competitive edge.”

The main reason for choosing Leica Geosystems’ products was the quality of their total stations. In addition to the specialised Leica Geosystems monitoring software, Terradata also uses its proprietary development TEDAMOS (Swiss Monitoring Solution by Terradata) to visualise the data.

Figure 9: In addition to automatic monitoring, a vast number of manual deformation monitoring tasks are performed.

Innovation is the only future-proof strategy

Terradata AG has a powerful company motto: “We measure and document – wherever buildings and soil play the main role.” The latter connects perfectly with Leica Geosystems’ slogan, “When it has to be right.” A strong equipment partnership during complex monitoring projects means that the customers need to be able to rely on their equipment 24/7. Terradata AG is eagerly expecting further technological innovations in the communication segment. Leica Geosystems is looking forward to additional exciting projects where safety is ensured with industry-leading hardware, software and service, all-in-all providing top-level monitoring solutions.

Interested in monitoring? Please feel free to read further case studies, showing how our customers use our solution to improve their monitoring workflow:

Monitoring Case Studies