Tunnel Projects Brochure (NA)

Tunnel engineers have trusted Senceive technology for more than a decade. It is designed and built for the tough demands of underground projects and provides precise, reliable structural and geotechnical data to help you address the unique pressures and challenges of your tunneling project.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Tunnel Projects

ADDRESSING YOUR CHALLENGES

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LIMITED TIME Ideal where only short access windows are available

PROTECT PEOPLE & INFRASTRUCTURE Early warning of distress and defects without leaving your desk

LIMITED SPACE & DIFFICULT ACCESS

Compact, autonomous sensors will not interfere with your operations

STAY ON BUDGET Use cost-effective monitoring for cost-effective tunneling

CHANGING NEEDS Adapt the monitoring system as your project progresses

TOUGH CONDITIONS Long life performance

As with any of our wireless monitoring solutions, a typical tunnel monitoring system will comprise three key elements : sensors, a cellular communications gateway and an online data portal. For dense sensor networks and highly responsive reporting, choose our FlatMesh™ intelligent mesh platform. Where sensors are widely dispersed and where you need to transmit data through physical obstructions (including soil and rock) our long-range GeoWAN™ platform may be more suitable. In order to relay data from the sensor positions deep underground to the Gateway that is typically located just outside the portal, repeater nodes may be used. Alternatively, Wi-Fi or ethernet connections can be used where available.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Chipping Sodbury Tunnel - Structural Monitoring CLIENT: AECOM / COLAS RAIL SRSA / NETWORK RAIL How the use of precise wireless triaxial tilt & optical displacement sensor nodes informed decision-making & ensured safety during track lowering & drainage works in a 4 km/2.5 mile tunnel

Challenge Chipping Sodbury Tunnel, near Bristol (UK), was completed in 1902. The twin track masonry structure is 4,000 m long and is the second longest tunnel on the Western Route linking London and South Wales. Network Rail has been implementing an extensive programme of improvements to the route since 2010 which includes installing overhead electrification. In order to accommodate the overhead line equipment (OLE), there was a need to modify many structures, including Chipping Sodbury Tunnel. Works included lowering the track by 150 mm and improving the track drainage. In the Autumn of 2020, AECOM engineers undertook a structural assessment to evaluate the potential impact of the track lowering works on both the tunnel and the central track drainage culvert. This assessment informed the implementation of a monitoring regime which was required to provide the necessary assurance that the works could be undertaken safely.

Devising a monitoring solution for Chipping Sodbury was not straightforward. Factors to consider included: the need to maintain continuous operation and data transfer from the system at distances greater than 2 km from access points; the need to avoid interference with the construction works and to avoid damage to the system arising from the works, and the need to maintain reliable monitoring performance in conditions that were, at times dusty, waterlogged and prone to significant vibration.

The monitoring scheme aimed to verify the findings of the structural assessment and inform decision making, particularly in the event of measurements exceeding predicted values. The monitoring design was guided by principles outlined in the British Tunnelling Society publication, ‘ Monitoring Underground Construction - A Best Practice Guide’ , alongside the Network Rail standard NR/L2/CIV/177 – ‘ Monitoring track over or adjacent to Construction Works ’. Monitoring design and arrangements also drew on experiences gained by AECOM on similar track lowering projects where structural monitoring was also required. This included several locations of the Great Western Railway Modernisation Scheme, namely; Patchway Tunnels, Box Tunnel, Middle Hill Tunnel, Dundas Aqueduct, Sydney Gardens, and Alderton Tunnel.

Key Points:

• AECOM engineers needed a monitoring scheme to verify findings of their structural assessment and ensure safety during construction works • Wireless monitoring solutions ensured a continuous data transfer in challenging site conditions • Sensors on the tunnel lining allowed the anticipated movements to be monitored without interfering with the works

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Solution AECOM chose Senceive’s FlatMesh™ Nano triaxial tilt sensor nodes as the primary technology for monitoring the tunnel lining. This was largely due to the associated operational advantages, including their compact size, robust construction and better performance in the wet tunnel environment compared to conventional tilt sensors. Over 200 Nano tilt sensors were installed on the tunnel lining to provide a flexible and high-resolution monitoring system able to capture the limited movements anticipated. The main limitation was that the sensors would measure relative, rather than absolute movements. Whilst this was sufficient to identify and quantify the anticipated modes of movement, a decision was made to provide supplementary monitoring to verify that the system and structure were performing as expected. This used tilt nodes mounted on beams. Wireless tilt chains – Nano tilt sensors mounted onto aluminium beams - offered an alternative to Shape Accel Arrays (SAAs); however, a review of gauging clearances showed that it would not be possible to install them around the full tunnel profile due to localized pinch points. Nevertheless, shortened tilt chains were installed in high risk areas where they could be safely accommodated.

In addition to monitoring the tunnel lining, track monitoring was also conducted. This used a total of 834 Senceive High-G Triaxial Tilt Sensor Nodes at 3 metre intervals throughout the main works area and 30 m beyond the zone of influence. Relative and absolute twist and cant were monitored. The absolute cant was calculated using surveyed cant readings, which was then used as a constant offset to the incoming data from these tilt sensors. There was a further need to check the behavior of the central track drain culvert, but access considerations prevented mounting instruments directly on the buried structure. A decision was made to monitor the track above to identify any deformation that could indicate failure of the drain. This was achieved using High-G Triaxial Tilt sensor nodes installed at 6 m intervals outside the main works area. Power for the gateways was not available via the usual options of solar panels or mains supply. This was solved by using 12v 110Ah batteries connected to a 12vdc to 24vdc converter. With periodic charging of the batteries this provided a reliable means of continuously powering the system and relaying data onwards to the WebMonitor data viewing platform. The system was configured to send automated alerts warning of any movement that exceeded pre-selected threshold values.

To further enhance performance, a number of Optical Displacement Sensors (ODS) were installed as a secondary means of monitoring at selected locations. The ODS nodes provided a different type of measurement (based on laser distance measurement as opposed to MEMS sensor) and were therefore considered to be a useful tool for verifying overall tunnel deformations. The ODS nodes were positioned in three modes: on opposing sidewalls; on the haunches pointing at the sleepers, and at the crown. The ODS nodes directed at the track were susceptible to interference from construction activity. The monitoring team therefore selectively paused ODS alerts when construction activity that interfered with line of sight was taking place in their immediate proximity in order to prevent false alerts being triggered.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Outcome The effectiveness of the monitoring program at this challenging site was built on a combination of the expertise of AECOM’s structural and monitoring engineers and the ease of deployment and reliability of the Senceive technology. The use of Nano and ODS sensors on the tunnel lining allowed the anticipated movements of the lower side walls to be monitored without interfering with the works. This was a key consideration given the restricted program of works (the tunnel closure was only three days) and the nature of the construction works which restricted access and line-of-sight. An extended program of monitoring was needed to verify the behavior of the culvert due to the changes in loading following the track lowering. As a result, monitoring was installed post-works on the down line track. Over 400 sensors were installed on the trackbed by two engineers within just four hours. Once movement was shown to be stable, the sensors were removed, with the rest of the monitoring equipment removed in the following weeks.

Over 400 sensors were installed on the trackbed by two engineers within just four hours.

The sensors will likely be re-deployed on a future AECOM project.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Box Tunnel Electrification - Structural Monitoring CLIENT: AECOM / NETWORK RAIL How a wireless monitoring solution supported major structural changes to a historic rail tunnel as part of Great Western Main Line electrification

Solution Conventional systems were considered impractical due to obstructed lines of sight, absence of power supply, long installation times and risk of damage. Monitoring experts at AECOM chose to use a Senceive solution to provide near real-time data relating to tunnel distortion that was wireless and did not need mains power. The AECOM team installed 250 Senceive tilt sensor nodes on a FlatMesh™ platform – providing sufficient coverage to monitor the full length of the tunnel. Data was collected through internal battery powered gateways and sent to users inside and outside the tunnel every 20 minutes to help verify predicted structural movements throughout the works. Additional innovations were made to allow for automatic switch-over to backup gateways in the event of damage or failure.

Challenge Network Rail’s Great Western Mainline electrification project started in 2014 to improve capacity and reliability. The route passes through the 3 km Box Tunnel, designed by Isambard Kingdom Brunel and completed in 1841. It was bored through four distinct strata and two fault zones and comprises 2 km of brick lined, 350 m of unlined and 450 m of brick arch construction. In order to achieve clearance for overhead line installation in 2015, there was a need to lower the track by 350 mm. To safeguard the integrity of the tunnel and minimize disruption to train operations there was a need to monitor and control movement. The challenge was to implement an economical, resilient and precise monitoring solution within a fully operational and congested construction site over the full length of the tunnel. Due to the live network, the system had to be wireless and mains power free.

Outcome The FlatMesh™ wireless solution met the very challenging requirements of this site, providing a solution where there was really no viable alternative. The system was delivered and installed in extremely tight timescales, necessitated by the fixed date of the line closure for the works. Additionally, safety was enhanced through the fast and simple installation. As the system was entirely wireless and mains power free, it was swiftly decommissioned at the end of the project, and the sensors reused, minimising waste, environmental impact, and whole life cost.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Spain

Costa Blanca - Martorell Tunnels CLIENT: INSTOP / DRAGADOS - TECSA

Innovative use of combined optical displacement sensors and tilt sensors to safeguard Spanish tunnels during major engineering programme Challenge

Solution The construction team required real-time 24/7 movement monitoring. They appointed survey and monitoring experts Instop to provide a Senceive wireless remote monitoring solution. This comprised of a combination of tilt sensors and optical displacement sensors (ODS) to detect rotational movement and convergence. The ODS method was novel in this application and provides a number of advantages over laser or optical techniques. Data from the various sensors were transferred from the site via a GeoWAN™ gateway located outside the tunnel. With no mains electricity available, an advantage over alternative technologies was the ability to power the system using solar panels. Easily installed by non-specialists, robust enough to last many years without maintenance and with no cables to interfere with other infrastructure, Senceive wireless remote monitoring has proved to be an effective solution.

Outcome All stakeholders were able to see changes in tunnel cross section from a real-time 24/7 data feed. Construction of the sprayed concrete lining and lowering of the track could therefore continue safely and efficiently with the reassurance provided.

As part of Spain’s ambitious Mediterranean Corridor, a number of disused tunnels were being refurbished. Spanish rail infrastructure operator ADIF appointed main contractor Dragados to upgrade three tunnels including the 810 m track tunnel between Martorell and Castellbisbal. The masonry structure had been disused since the 1980s and required relining with 4,500 cubic metres of sprayed concrete, the construction of overhead line electrification and track lowering. In order to safeguard the structure and the workforce during the construction work, there was a need for a reliable and accurate monitoring programme, but a conventional approach using optical survey methods was not an option due to the nature of the site: • No mains power in the tunnel which is at a remote location • Ongoing construction activity and use of heavy machinery • Conventional monitoring using automated total station was not possible due to no line of sight

The solution proved highly cost-effective to the client as it was provided on a four month hire basis.

Installations were done in record time at a speed of 4 sections per hour (3 nodes per section) or 100 m per hour, a complete tunnel in a working day.

Senceive regional distributor Instop supervised the installation of the monitoring system, which comprised of: • Martorell: 87 ODS sensors, 35 triaxial tilt beam sensors & 9 4-channel VW nodes to extensometers • Costablanca: 99 ODS sensors and 96 triaxial tilt beam sensors • Castelbisbal: 105 ODS sensors

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Netherlands

Botlek Railway Tunnel - Deformation Monitoring CLIENT: IV-INFRA B.V. / A-LANES A15 How Senceive technology supported construction and 25-year structural health monitoring Challenge

Solution Iv-Infra installed a total of 434 FlatMesh TM triaxial tilt sensors. These were located at points every 30 m through the tunnel, with nodes fixed to six of the seven segments in each ring. These were set to take readings every 30 minutes. The tilt node triaxial capability meant they could be positioned at any orientation, with no need for time-consuming levelling surveys. To overcome the lack of internet/cellular connectivity, Iv Infra used Senceive monitoring hubs positioned 800 m from each portal to receive data from the wireless nodes. The hubs were setup to utilize the tunnel’s 220 V power supply and relay data via a 2 km telecommunications cable to a telemetry hub located outside the tunnel. This transmits data through a mobile network to visualization software.

Outcome Iv-Infra opted to use their own software to read and process the data, however Senceive’s WebMonitor software also allowed the support team to remotely check system health. FlatMesh TM triaxial tilt nodes were the ideal choice, as they could be installed quickly and easily. This reduced man-power requirements, accelerated program and saved money. Senceive customer support team provided training and advice throughout the project. The extremely reliable and robust system also eliminated the need for any further maintenance or visual checks. For example, when construction works above ground commenced, Iv-Infra requested the reporting rate of the nodes to be increased to 7.5 minutes in certain areas. The system allowed this to be done remotely with no physical intervention. Monitoring is due to continue for the full 15 year battery life of the nodes. Batteries will be replaced at that point and monitoring will continue for a further 10 years.

The Botlek railway tunnel was the first bored railway tunnel to be built in the Netherlands. It is located near Rotterdam under the Oude Maas river and next to the existing Botlek railway bridge. Designers were concerned about possible ground movement and deformation associated with ongoing infrastructure projects in the area. A robust monitoring program was therefore required during and after tunnel construction. A monitoring system was required starting from mid-2017. The system had to be easy to install, as well as accurate, discreet and reliable. The 8.65 m diameter concrete segmental lining tunnel is 1.8 km long. No cellular phone signal or internet access was available. The design team predicted ground movement of up to ±3 mm. Dutch survey and monitoring experts Iv-Infra were engaged by the construction team and contacted Senceive to find a solution.

Fig.1 Cross section showing monitoring arrays on tunnel ring segments

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Regent’s Crescent - Structural Monitoring CLIENT: MURPHY GEOSPATIAL

How Murphy Geospatial incorporated wireless monitoring into their structural and environmental monitoring program during demolition and construction works for a major redevelopment near Regent’s Park, London

Challenge This was a major redevelopment of an iconic crescent near Regent’s Park originally built in the 1820s and designed by the renowned architect John Nash. The plan was to demolish the existing structure behind the original façade – which was to be completely refurbished – and for the excavation of new basements. The demolition was carried out by specialists McGee and construction undertaken by Midgard, for the client. Murphy Geospatial was tasked with crucial structural and environmental monitoring in and around the site including monitoring the London Underground, as the Jubilee line runs beneath the development and the Metropolitan line runs adjacent to the site. They needed to install, commission and maintain three automated multi stations in a live demolition site in close proximity to operational construction plant and with demolition works underway. They also installed more than 250 Senceive FlatMesh™ wireless tilt sensors in the Jubilee line tunnels, which were maintained throughout the multi-year project.

The monitoring of neighbouring properties, which included medical surgeries and other sensitive facilities, required great thoughtfulness because of the proximity to the demolition and construction works. Real-time data was provided to inform the construction company and all stakeholders to ensure that the agreed parameters were not exceeded and that third parties were protected from any noise and other disturbances to enable the construction works to be carried out on budget and on schedule.

Murphy Geospatial installed the following systems above and below ground: • 3 laser scan station sensors (AMS) • 300 Senceive tilt sensors - 250

below ground and 50 above ground

• 3 optical automatic total

stations and manual back-up survey equipment

• 3 digital image capturing devices • 20 seismic vibration sensors • 10 air pressure and noise sensors • 4 air quality and dust sensors • A wireless data transfer mesh network • IoT data communication facilities and alarm systems • Remote-controlled cameras

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Outcome This was a complex and highly sensitive project, which required the use of remote monitoring solutions to enable measurement without attaching reflectors to the building façade, and other technical innovations to transmit data wirelessly from various sensor types.

Solution In addition to the building and environmental monitoring, Murphy Geospatial was also required to monitor the structural health of 600 m London Underground tunnels. They did this by installing 250 Senceive tilt sensors in sections of five sensors around the circumference of the Jubilee Line tunnels and optical automatic total stations for the larger open tunnel sections of the Hammersmith and City Line. The long distance to the next station required ingenuity for the monitoring data transmission. The limited diameter of the tunnels and the proximity of excavation works needed special, newly developed algorithms to automatically calculate the deformation, heave and settlement of the tunnel structures. All sensors were managed remotely from Murphy Geospatial’s London office and the three integrated cameras enabled visual oversight of the site works.

In order to reliably relay sensor data to communications gateways located at tube

stations many hundreds of metres away, Senceive recommended the use of a fibre optic cable. This enabled the FlatMesh™ tilt sensors to report at high frequency and was found to be “a reliable and elegant solution” by the Murphy Geospatial team. By combining technology and software from Leica Geosystems and Senceive, Murphy Geospatial was able to developed the so-called ‘patch scan’ solution. This has been adapted by the industry in new specifications for large-scale monitoring projects, avoiding drilling holes into a façade and reducing installation times.

This project was shortlisted for both construction and tunnel awards.

Figure 3: Jubilee Line 3D model with Senceive’s tilt sensors

Figure 1 & 2: 3D movement model from Senceive’s tilt sensor data before and after demolition, showing heave of tunnel

Source: Bowles & Wyer

Harnessing intelligent monitoring technology to keep people and infrastructure safe

France

Monaco – L’Anse du Portier Structural Monitoring CLIENT: GEOMESURE / TOPOSUD / BOUYGUES TP How landmark French Riviera project benefitted from wireless remote monitoring of critical structures

Challenge In 1971, the Principality of Monaco agreed to a 30 m development project: the Complexe Immobilier des Spelugues. The complex, with its hotel, convention centre and apartments, was built over Boulevard Louis II road on 15 metre concrete columns overlooking the Mediterranean Sea. Four decades on, land scarcity led the Principality to expand into the sea once again, with the development of a new 6-hectare district, l’Anse du Portier. Construction included: • Removing existing rip-rap and dredging 600,000 m 3 of polluted silt • Backfilling and vibro-compacting 1.5 m tonnes of rock • Installing 18 concrete caissons measuring 27 x 28 m and weighing 10,000 tonnes • Importing 750,000 tonnes of new soil • Installing 1,100 piles In order to manage the risk of disruption or damage to the original Spelugues complex, an accurate and reliable monitoring system was needed.

Solution Regional surveying experts, Toposud first contacted Geomesure, Senceive’s French distributor, for technical advice. They wanted to continuously monitor the beams and columns without the unsightly cables and limitations of a fixed optical system. They chose the FM3N-IX FlatMesh TM 3 Triaxial Tilt Sensor Node as it offered: • Easy installation. The wireless mesh system was quickly installed and data was immediately transferred through the congested underground space without any line of sight or reference issues. • A robust system. Because the tunnel is partly open along the shoreline, equipment would be exposed to saltwater spray. Senceive’s IP68-rating and track-record in saline environments assured the team that corrosion would not be a problem. • Precise monitoring. Installed on structural elements with known geometry, the triaxial tilt sensors measured both rotational movement of the columns and differential settlement of the slab.

Outcome The small battery-powered nodes and solar powered battery were discreetly installed on the structure without requiring power/data cabling or heavy anti-theft protection. The batteries can operate for up to 15 years without being replaced. A Senceive cellular gateway connected to the local network enabled all stakeholders to access structural data at any time of day, regardless of their location. The system was configured to send text or email alerts to more than 25 people in 9 organisations in the event of any threshold breaches. Benefits of the Senceive wireless solution include enhanced health and safety and significant cost savings on installation, maintenance and site access.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Rotherhithe Tunnel - Deformation Monitoring CLIENT: TFL/ TIDEWAY EAST / SIXENSE

Senceive and Sixense worked together to design and implement a monitoring programme to safeguard crucial London road tunnel during construction of a nearby tunnel shaft Challenge Solution

Outcome Senceive provided a fully wireless and flexible monitoring system which could be installed quickly and easily within the short night-time closures. The installed system was sufficiently robust to operate for years without maintenance - therefore avoiding the disruption, cost and potential risks associated with repeated site visits. Impact on the structure and damage to the tiles was minimal as the nodes required just a single mounting point and minimal cabling. The Senceive and Sixense teams worked together to modify tiltmeter fixings in order to incorporate a 3D prism needed for optical instruments - thus avoid duplicate fixings. The IP66/68 tilt nodes with protective caps were found to be unaffected by the twice-monthly tunnel cleaning and also provided physical protection to the antenna. The monitoring continues to provide reliable, precise and repeatable data until the Thames Tideway Tunnel is set to complete in 2023. The tilt nodes have a battery life of 12-15 years, allowing for the option to further extend the monitoring duration.

The Thames Tideway Tunnel will capture, store and move almost all the untreated sewage and rainwater discharges that currently overflow into the River Thames in central London. The Rotherhithe Tunnel sits in close proximity to the Tideway East shaft site and there was a need to ensure that the construction work did not threaten the integrity of the tunnel. The CVB consortium (Costain, VINCI Construction Grands Projets and Bachy Soletanche), along with Sixense as their appointed monitoring contractor, required a monitoring system in place 12 months ahead of shaft construction to provide an adequate period of baseline monitoring. They required the monitoring program to continue through the works and for a period after construction until any associated movements had ceased. Access was only allowed during night-time engineering closures that took take place once per week. Another challenge was that the majority of the tunnel lining is tiled and is very delicate and as such, owner Transport for London was reluctant to allow intrusive structural fixings. They were also concerned that the monitoring system should not be affected by fortnightly tunnel cleaning operations that involve a mechanical process including spinning brushes and high pressure hot water jetting.

Monitoring experts at Sixense chose the Senceive FlatMesh™ wireless system as their monitoring solution. A total of 74 high precision tilt sensor nodes were installed during engineering closures over an eight-week period to monitor any convergence/divergence during the works. Of these, 64 were installed directly onto the tunnel lining in 16 arrays of four nodes. A further 10 nodes were mounted on three-metre beams in a vertical shaft. The FlatMesh™ system allowed all the nodes to communicate with each other and measure sub-mm movements for an estimated project duration of 3-5 years. The data were transmitted to two wall-mounted 3G gateways, positioned and powered at the base and top access chamber of Shaft 3, with the data being relayed and transmitted via an antenna at the top of this shaft. From there, data were sent securely via the mobile GSM network and accessed by registered users of the Senceive WebMonitor data visualization software and the client’s own software. The nodes could also be remotely configured to provide near real-time data frequency if required.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Monitoring Assets Affected by London Power Grid Tunneling CLIENT: COSTAIN/BT TUNNELS

How wireless remote monitoring helped to safeguard critical assets affected by tunneling activity and supported efficient progress of tunnel boring machines Challenge

Solution Costain engineers worked closely with Senceive experts to devise appropriate and cost-effective solutions. In Camden, for example, a series of interconnected aluminum beams, each with a high-precision dual axis tilt sensor measured longitudinal settlement along a 100 m section of BT tunnel. With no wires, the installation was quick and easy. The movement sensors were connected via a gateway and BT’s own lines. Stakeholders could see and interact with the feed of monitoring data which was updated four times an hour. At the Thames embankment site, tilt nodes were installed on beams on the river side of the wall. Data was relayed wirelessly to the WebMonitor cloud server via solar-powered GPRS gateway.

Outcome Each of these projects lasted several months and was effective in reassuring owners of third-party assets that movement levels were generally well within acceptable tolerances. As a result, a number of other sites affected by the London Power Tunnels project chose to use Senceive technology to safeguard at-risk infrastructure.

In February 2011 National Grid embarked on a seven- year project to upgrade London’s electricity grid. This involved construction of a series of tunnels to house 400kV power cables, boosting capacity and access to renewable energy. Main contractor Costain was responsible for the civil engineering work. Tunnel routes connected Willesden in the west to Kensal Green and Hackney in the east. A north-south route extended from Kensal Green to Wimbledon. Two tunnel boring machines (TBMs) were used to build the 32 km of tunnels. Costain was also responsible for monitoring assets along the route that may have been affected by the tunneling. They used Senceive technology at several sites where there was concern about the risk of settlement affecting critical assets, including British Telecom (BT) communications tunnels, the River Thames embankment wall and London Underground railway tunnels.

KEY POINTS

• Complex tunnelling operations took place in close proximity to other critical infrastructure. • Wireless monitoring solutions were quick to deploy and were adapted to work in varying conditions above and below ground. • Monitoring data reassured asset owners and allowed tunnelling to go ahead with confidence.

Harnessing intelligent monitoring technology to keep people and infrastructure safe

United Kingdom

Track Monitoring: Victoria Station CLIENT: LONDON UNDERGROUND/TWBN

How the flexibility and mobility of FlatMesh™ enabled a grouting team to stabilise ground below London Underground tunnel at Victoria Station without damage to track

Challenge The upgrade to London’s Victoria Railway Station was a large and complex undertaking. As part of the project, an underpass had to be tunneled directly beneath a shallow brick-lined tunnel carrying the District and Circle Line. In order to stabilise the permeable ground before the tunneling took place it was treated using the TAM grouting process. The work had to be conducted during short Engineering Hours access windows. In order to manage the risk of ground heave damaging the tracks, the client required a real-time, high-precision monitoring solution that could be quickly deployed during each shift. Optical methods were rejected because lines of sight could not be guaranteed. Wired monitoring systems were also rejected because they would have been prone to damage and would have been slow to deploy. A wireless monitoring solution using the Senceive FlatMesh™ platform was selected.

Solution During grouting, movement could occur in any part of the 30 metre zone across two separate tracks. TWBN employed Senceive’s patented and specially upgraded magnetic mountings to secure the 20 wireless sensors directly onto the surface of the rail. Using the highly responsive FlatMesh™ wireless communications platform the system was operational within a few minutes of installation at the start of each shift. It was able to report any movement in excess of 0.009 degrees of angular tilt. Reporting frequency was set at no more than one minute. All this was carried out without signal or power cables.

Outcome The sensors communicated in real-time to a gateway attached to a laptop computer on the site. For this project, functionality was added to ensure that clear visual alerts and audible alarms would be triggered by any movement above pre-set trigger levels. This meant that the computer did not have to be permanently manned, allowing the engineer responsible for monitoring to complete other tasks. The data were characterized by a high level of stability throughout the grouting program. The small levels of movement that were identified were corroborated by levelling surveys. No false alarms were raised. This unique use of Senceive’s award-winning tunnel and rail-focused technology was installed on site within three weeks of the initial proposal. Senceive specialists worked alongside shift engineers for the first two nights, to ensure all was well and the system was fully understood. After that, the monitoring was exclusively carried out by TWBN engineers who were extremely pleased with its overall performance and benefits.

KEY POINTS

• Installed and removed for every night shift

• Operated by non-specialists • Sub-minute reporting intervals • Reliable, precise measurement of movement enabled ground stabilization team to operate with confidence

Harnessing intelligent monitoring technology to keep people and infrastructure safe

Contact Dan Miller if you want to find out how remote monitoring can make your tunneling project safer and more efficient.

Dan Miller dmiller@senceive.com New York

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