Sixense Mapping carried out a high density (1000 points/m²) helicopter-borne LiDAR measurement of the summit of Mont Blanc as part of a commercial scientific mission. This measurement, which took place two weeks before the “official” biennial measurement by the French chartered surveyors’ association, is the subject of a detailed article in the December 2021 issue of XYZ, the journal of the Association Francophone de Topographie (French-speaking association of topography).

The use of LiDAR for such a measurement is a first, Mathieu Peyrega, development engineer at Sixense Mapping, explains:

“This alternative method to mountaineering expeditions and conventional topographic techniques allows for a measurement of equivalent accuracy. The result, to our knowledge, is the highest density source of information ever produced on the roof of Western Europe, with an accuracy level fully equivalent to traditional survey techniques.”

In addition to the experimental validation of potentially being able to use our sensors in these extreme conditions, the obtained measurement accuracy (+/- 10cm@95%) is identical to the terrestrial methods and confirms the effectiveness of this technique. The short implementation time makes it possible to use it with a reactivity that is not possible with conventional approaches.

The results obtained, correlated with the weather conditions observed between the two measurements, bring a new perspective on the “short-term” movements of this emblematic peak, which has moved by nearly 13 meters in planimetry and nearly 1 meter in altimetry over the period. In a way, this leads to relativise the “absolute” interest of a centimetric precision measurement in this specific context.

However, for us, this remains an exceptional flight that illustrates the extent of our systems’ capabilities, our teams, and our ‘know-how’.

A major bridge project allowing a safer, easier, and toll-free commute

The existing Pattullo Bridge is an arch bridge that connects New Westminster and Surrey and provides on average 75,700 cars and 3840 trucks a daily option for crossing over the Fraser River in the Metro Vancouver area. At the start of 2020, Fraser Crossing Partners (a joint venture between ACCIONA and Aecon Group inc ) was selected to design and construct the replacement bridge. The improved crossing will feature four modern, wider lanes for traffic, with allowance for a potential future expansion to six lanes, pedestrian and cyclist access, and better connections to, from, and near the bridge. 

Multi-stakeholder project site requiring innovative and safe solutions

A light rail tunnel, two additional bridges (one light rail, one heavy rail) and the existing Pattullo Bridge, are all located within proximity of the location of the new bridge alignment. Sixense was chosen by Fraser Crossing Partners to develop a monitoring solution that will encompass the surrounding major structures and railways enabling continued safe use of the nearby infrastructure throughout the Project construction.  

Through coordination and cooperation with a variety of infrastructure owners, Sixense has designed and implemented a comprehensive monitoring solution, including 13 Sixense patented Cyclops AMTS systems monitoring hundreds of prisms, 9 4D-BLOC GNSS sensors, 28 vibration monitors and 46 wireless tilt sensors.  

An ongoing partnership until the project completion

The innovative monitoring system will be actively administered and maintained by Sixense, delivering near-real-time data on the Geoscope platform to all involved stakeholders. Uninterrupted, safe operation of all surrounding infrastructure will continue to be enabled by the Sixense solution through project completion.

Brest Metropole, in France, plans on operating a second tramway line as well as a High Level of Service Bus line (also called Busway or Trambus) in 2026. Their route includes the Clémenceau Bridge, an infrastructure built 30 years ago. However, this one has not been designed to support the weight of tramway and High Level of Service lines in addition to the road traffic. 

The contracting authority entrusted Sixense to perform the investigations and checks needed on site to refine the sizing of the reinforcement work planned on the structure, in anticipation of the new tramway crossing and the bus line. To do so, our teams carried out load testing during the night of the 25th to the 26th of February 2021.  

In order to successfully complete the operation, the traffic was stopped to make room for several loaded trucks of a total weight of 120 tons. The bridge has been equipped with targets on the beams supporting the bridge, all aimed by a theodolite which was itself connected to computers with our Geoscope software, recording in real time the least oscillation of the loaded structure.  

Nicolas Sanchez, our team leader in charge of this operation explains:  

“An infrastructure is designed for a certain traffic. It is very likely that it will need to be reinforced. It is already more or less what is expected. We have installed a prism under each 17 beams. We target each beam with a laser equipment. The aim is to see, when loaded, the infrastructure’s deformation. We immediately receive the raw results, but we will still have to process all the information in order to provide results for the Brest Metropole Organisation” 

Our design offices specialised in climate resilience, Resallience, assists the Deposit Fund Caisse des Dépôts (CDC) Habitat with its adaptation strategy to climate change. They joined forces with our experts in engineering of existing structures to develop the first DPR platform (Climate Resilience Performance Diagnosis).

It is a decision support system composed of, on one hand, a hypervisor, powered by a geographical information system, and on the other hand, an analytical spreadsheet. The DPR allows to assess the criticality level of built heritage to climate risks. It also analyses the technical and financial risks of impact of these contingencies on the components, the subsystems and the systems of the groups of buildings. The DPR applies to all the property assets of CDC Habitat, close to 500 000 housings, and will allow to power the pluri-annual plans of investments to restore this heritage, to adapt the design of the new constructions and this way, better adapt to climate change on the horizon of 2050.

This project comes within the scope of a partnership between CDC Habitat, the FFA Insurance (French Federation of Insurances and the association of natural risks mission – MNR) created in 2000 by insurers in order to contribute to a better knowledge of natural risks.

Discover the article from CDC Habitat for more information.

The Normandy Bridge, a major structure that stands up to the elements

Since 1995, the Normandy Bridge is crossing the Seine estuary and connects Le Havre and Honfleur by a 2,141-meter long prestressed concrete and steel structure. It has a cable-stayed span of 856 meters. The deck of the structure accommodates 4 vehicular traffic lanes as well as bicycle and pedestrian paths. Its 184 stays, with up to 53 strands for the largest cables, ensure that the central steel deck is maintained for no less than 654 m above the navigation channel.

The durability of this structure, a symbol of French know-how in terms of Civil Engineering but subject to the winds and tides at the Seine estuary, is ensured by regular and rigorous maintenance. This maintenace is backed by the monitoring of the structure with a set of specific sensors but also by the periodic control of the structure’s and particularily the ageing of the stay cables

Increased surveillance of the structure to ensure its durability

Between 2011 and 2018, Sixense installed and maintained a monitoring system composed of about a hundred sensors: displacement, inclination, force in the stay cables, temperature, vibration of the structure, weather station and even breakage of stay cable wires. This system, which measures both the external stresses and the structural responses of the structure, enables a better understanding of the structure and anticipation of maintenance operations.

Since 2011, Sixense has also carried out periodic testing of the stay cables to determine their level of aging and check their residual structural strength. The Uscan process, patented jointly with the Gustave Eiffel University, works on the principle of ultrasonic guided waves to check the health of the strand wires in the areas where the stay wires are anchored.

Thanks to these continuous and periodic measurements on the sensitive componentss of the structure, the CCISE* can anticipate and schedule maintenance operations that will keep this masterpiece of French Civil Engineering intact for many years to come.

CCISE*: Seine-Estuaire Chamber of Commerce and Industry

A major high-speed railway project across the UK

High Speed 2 (HS2) Phase 1 is a large high-speed railway project in the United Kingdom which will link London and Birmingham, with a future second phase to reach Manchester and Leeds in Northern England.

This major project will provide increased capacity and reliability of the railway links and should help manage the rising number of passengers.

HS2 phase 1 is expected to open to passengers in 2026 and Phase 2 around 2033.

Sixense expertise applied to this environmentally challenging major project

Sixense is excited to embark on the significant challenge of providing noise, vibration and air quality management services on a section of Europe’s largest infrastructure project, HS2. This section of the mega engineering project, delivered by Align JV, includes the route’s flagship 3.4km-long Colne Valley Viaduct, as well as the 15.8km-long Chiltern twin-tunnels. The services to be provided by Sixense include a significant amount of monitoring, modelling and assessment work across the 10+ worksites, which will play a key role in the wider efforts to minimise environmental impacts throughout the 5-year build.

Sixense teams providing efficient solutions

Within the first six weeks of its involvement, Sixense already installed 22no. noise and air quality monitoring stations, which are largely powered by sustainable-energy sources.

Sixense would like to thank the consortium in charge of the works for their trust on this new project of the Grand Paris Express. The forecast duration of this new contract for monitoring of the works and nearby infrastructures is of 5 years. Line 18 will be about 35 km-long from the Orly Airport railway station to the Versailles-Chantiers railway station.

The market, notified on May 14th of 2020 to the association of several entities of @Vinci Construction and @Spie batignolles, includes the realisation of :

• a bored tunnel of about 11 800 ml, of 7,8 m of effective diameter excluding crossing of structures,
• trenches (cut and covered) of about 850 m between the tunnel and the aerial section comprising the temporary reorganisation of the Croix de Villebois road crossing intercepted by the works,
• structural works of the underground railway stations of Antonypole, Massy-Opéra and Massy-Palaiseau,
• thirteen annexed works, including the connecting branches of the tunnel.

Sixense Monitoring was assigned the auscultations to be carried out in the framwork of the project related to the drilling of the tunnel and to the construction of the infrastructures (excluding Launching shaft and Cut & Cover and excluding inside topography of the railway stations and right-of-ways).

This sector comprises 2 very sensitive areas which will need to be carefully monitored : the important railways nearby the future Massy-Palaiseau railway station and the Orly Airport area.

A permanent Sixense team will remain on the field at the base of the worksite in order to stay as close as possible to the work teams to carry out the mission that we have been assigned to. The team will implement a diversity of auscultation measures, including:

1. Automated topographic monitoring with our now well-known Cyclops and Centaurs which will examine the nearby infrastructures of the project,
2. Measures by inclinometers of the vertical structures of the infrastructures under construction,
3. Stresses and constraints monitoring of the infrastructures under construction or the instrumented voussoirs,
4. The geotechnical monitoring of the 16 sections of reinforced measures of the 2 tunnels comprising inclinometers in the field, multipoints extensometers in boreholes and interstitial pressure cells.

Geoscope will be the management support tool for all companies to access all auscultations of the project. This tool had been designed with a multi-actors approach allowing all different parties of the same project to have access to all the useful data : intuitive visualisation of the data, management of the alarms for level exceedances, visualisation of the construction site progression and access to all reports of auscultations.

This project is once again an opportunity for us to implement our monitoring expertise of urban works build up throughout the years with tunnel projects in urban areas where we have been able to step in.

Sissterra, a solution for worksites having an impacting on underground subsoils in restricted environment

Boreholes and other invasive geophysics investigation techniques are not very well adapted and difficult to deploy in restricted environment such as dense urban areas. Having a good visibility of the underground is however always necessary to carry out these works in such spaces.

It’s the reason why our experts developed an innovative geophysics solution, based on seismic without sources and particularly adapted to dense urban areas: Sissterra.
Based on a passive technology, our solution allows to reduce the number of boreholes and avoid active seismic sources. Sissterra passive technique relies on ambient noise recordings in the underground by autonomous geophones, an easy-to-use and easy-to-deploy system on site.

A turnkey and robust solution

An innovation from the academic field and the world of Oil&Gas, Sissterra is a turnkey solution allowing you to have a global visualisation of the underground subsoils. Our experts in geophysics manage the entire data value chain and can advise you from the reflection phase from your geophysics challenges, and this until the risk evaluation, going through acquisition as well. Sissterra is a tool that helps manage risks associated to the underground as it allows to consolidate the geologic model. The global visualisation ahead of the works allow to anticipate the adjustments of the constructive methods to maximise the site productivity.

Discover the solution in video:

Whilst tunnelling using traditional method, the geologists usually carry out regular “manuals” cutting face mappings using a combination of field observation and pictures. But this method is not optimised as the pictures are not “at scale” and are often distorted and therefore, not representative of the actual geometry of the cutting face.

The new photogrammetric solution Pika allows a true and instant 3D reconstruction model of the tunnel face.
The geologist simply takes a few pictures of the tunnel face, then drops off the images on the Sixense Mapping beMap online platform. A Few minutes later, an ortho-image, a 3D map, a point cloud and a mesh are all made available through beMap.
All those files are a true representation of the reality, for both the geometry and the texture.

With Pika, the geologist therefore has access to:

• The lithology and/or the mineralized veins, with real appearance, size and thickness
• The location and the orientation of the fractures and cracks
• The 2D-3D visualisation of all successive tunnel faces, one after another
• The exact measurement of size, distance and surface of anything on the models

Precision, time saving, data storage: Pika facilitates geologic follow ups of excavation works.

Pika is a Sixense Mapping solution.

More information : mapping@sixense-group.com & natacha.robert@sixense-group.com

Sixense takes part in writing international monitoring standards

A group of about ten European experts has been working since 2010 on writing international monitoring standards.

Sixense is involved in the project via Martin Beth, director of our Monitoring Division France, by representing France among monitoring specialists from all over Europe, in charge of elaborating European and worldwide standards (CEN and ISO).

Their aim is to help sharing best practices in monitoring, by coordinating and writing them collectively.

Our expert explains :

Each standard takes between 2 and 3 years work in average and we will prepare about ten of them in the following years. The basic standard on general rules was published in 2015, followed by the standards on extensometers, inclinometers, piezometers and pore pressure cells. Our group is currently working on standards for liquid level settlement sensors, strain gauges and load cells and will start working shortly on geodetic monitoring instruments (automatic theodolites for example).

Martin Beth, director of Monitoring Division France, Sixense

Ultrasonic inspection and Acoustic Monitoring of the Ile de Ré Viaduct 

The Ile-de-Ré Viaduct in France experienced in 2018 a failure on one of its external prestressing tendons. The bridge owner awarded to Sixense and Freyssinet the mission to secure the structure, inspect ultrasonically the existing tendons, monitoring acoustically their potential failure and replace the broken tendon.

EverSense® Acoustic monitoring and cable replacement are well experienced skills of Sixense and Freyssinet. However, before Ile-de Ré Viaduct, EverScan® ultrasonic inspection of anchorages has only been done on individually sheath waxed strands of stay cables but not on grouted bare strands of prestressing tendons. On prestsressing tendons the risk of failure has clearly been identified and located in the first meter away from the tip of the strand in the anchorage zone, which is further away than stay cables application.

Then Sixense and Gustave Eiffel University (UGE, formerly IFSTTAR) worked on the extension of the ability of the well known ultrasonic USCAN® technology in order to apply it on grouted strand and up to 2 m away from the anchorage.

For this project 85 anchorages have been inspected by USCAN® and 170 acoustic sensors were installed prior to the replacement of the broken tendon. USCAN® measurement resulted in identifying 3 anchorages in bad condition with potential failure. The worst tendon has been removed for replacement. Visual inspection of removed anchorage piece confirmed the blind measurement of USCAN® and showed the ability of the technology to detect failure and corrosion in strands near anchorages.

This emergency job was made in less than 6 months. Today the viaduct is under high acoustic monitoring by Sixense teams for any detection of wires breaking.

Sixense Mapping’s partnership with Topcon positioning Group to expand in africa          

As a reference in 3D digitisation of existing assets, Sixense Mapping signs today a partnership with Topcon positioning Group to develop their activity in Africa. The common ambition is to fulfil the needs for digital transformation in the African markets of construction, infrastructures, mines and agriculture.

As an international Group, Topcon is a reference in technologic solutions for constructions such as 3D guidance for jobsite machinery. Topcon is present in Africa through a dense network of reseller, ensuring a busy activity for clients, their projects and local jobsites.

Sixense Mapping just broaden its services offers on one hand, its acquisition solutions by drone, LiDAR on board helicopter or even Mobile Scan already carried out in France and Europe, and on the other hand its data management solutions for a better operational performance:

• Change detection: remotely monitor engineered structures, natural areas (cliffs, vegetation…);
• Exploitation follow up: surfacing project optimisation, monitoring of earthworks, monitoring of quarries & mines.

Structural Deformation Monitoring of Hampton Roads Bridge-Tunnel Expansion project using AMTS and high precision low cost GNSS.

The $3.8 billion Hampton Roads Bridge-Tunnel Expansion project is the biggest project in the Virginia Department of Transportation history which includes constructing twin bored tunnels west of the existing immersed-tube tunnel and bridge.

Sixense was chosen by the design-build team Hampton Roads Connector Partners (HRCP) (consists of Dragados USA, Flatiron Construction, VINCI Construction Grands Projects and Dodin Campenon Bernard) to perform baseline deformation monitoring of the existing tunnel, approach walls as well as several facility buildings on the south and the north islands connected by the crossing from August 2019 to August 2020.

A robust near real-time deformation monitoring system was designed and implemented using 9 Sixense’s Cyclops automatic motorized total station (AMTS) systems, complemented by nearly 50 novel 4Dbloc, low-cost high-precision GNSS receivers and over 60 wireless tiltmeters.

In recognition of the high quality work performed by Sixense during the 1^st stage baseline monitoring, a new contract for transition baseline monitoring into active construction stage monitoring was recently awarded to Sixense, in August 2020, with an expanded scope of monitoring work including a significant amount of AMTS, vibration monitors and other geotechnical instruments.

With 500 m span and its single pylon Komárom bridge is linking Hungary and Slovakia 100 km West from Budapest. Sixense has the mission to design, fabricate and install a full EverSense® Structural Health Monitoring System (SHMS) . 

The system includes different type of sensors such as stay cable load sensors, bearing displacement, temperature, video cameras and a weather station with an integrated road surface condition sensors. 

The EverSense® SHMS will allow to follow the behavior of the structure, alert in case of abnormal activities and ensure the security of the user.  

In a few years the operator of the bridge will use the data generated by the system in order to plan its maintenance and secure the design life of the structure. 

Installation of the system went through during the COVID-19 lockdown period which made it more challenging. Thanks to our local entity Sixense Hungary, the installation was made possible despite lockdown with remote assistance from our SHMS experts. 

The bridge was inaugurated mid-september 2020. 

Sixense is developing skills in areas with difficult access, including inspection of dam infrastructure.

Destination the “Provençale” region, more precisely the Saint-Victoire Massif close to Aix-en-Provence, where Sixense was called for a periodic inspection mission by the Société du Canal de Provence (SCP), who manages the Zola Dam installations.

Built in 1854 and named after the architect François Zola, father of the writer Emile Zola, the Zola Dam requires periodic inspections and recording of faults on the emerged parts of the structure to assess the state of the dam.

In order to inspect closely the whole surface of the dam at 36m high, our teams carried out the intervention with ropes and harness.

In 2011, a specialist rope access team carried out the inspection alongside our engineer who joined on some of the descents to observe the faults.

But on this recent occasion, and for the first time at Sixense, our engineer, who is also a qualified CQP rope access technician, could carry out a rappelling descent alone. ATOMS provided support in the form of access materials and equipment as well as know-how (anchors set up, descent supervision, presence in case of emergency).

Cédric Laurent, in charge of realisation, is a difficult access specialist at the BEI department:

« the walking trail on the crest of the dam stayed opened during the mission and several different strengthening works down the dam made the intervention quite sensitive. Moreover, the weather conditions and the bushfire risks in the Saint-Victoire Massif meant we could only work from 6am to 1pm. The good preparation of the mission (pre-start site visit, regular discussion with the client, evaluation of the risks…) was a key element for the success of the mission. »

This intervention method allowed us to accomplish quality recordings by an expert inspector, and to optimise the time spent on the jobsite thanks to the reduce number of rope access technician and descents needed.

With dual skills in rope access and in specialist in diagnosis,  our Sixense Engineering team can now offer a solution for future interventions on ropes such as inspections, diagnosis, and instrumentation for tall infrastructure where more typical means of access (mobile elevating work platform, scaffolding) are impossible, such as for bridges, stadiums, retaining walls, water towers and chimneys.

We are delighted to announce that a consortium led by Sixense and Imperial College London (with support from experts at Royal Holloway, Crossrail and Thames Tideway) has been selected to produce a CIRIA (Construction Industry Research and Information Association) guidance report on the application of ‘Earth Observation and InSAR technology in civil infrastructure’. This report will draw on the extensive experience of the consortium members and will detail current practices, illustrated with case study examples, and outline respective advantages and limitations of the various techniques to assist all users and, in particular, those involved in asset management and construction. A separate online database of case studies will also be developed in parallel by CIRIA to support the guidance document. We understand that this document will form an important review, of current practices and ongoing developments, to inform newcomers to Earth Observation as well as those already using such technologies.

Civil engineering and infrastructure (construction, maintenance and monitoring) are activities which demand high spatiotemporal accuracy, precision and detail of observations and measurements. Satellite borne remote sensing techniques are now able to produce data and information of a quality which satisfies such requirements. Yet there are few standards and regulations for best practice in the production and use of Earth Observation products. CIRIA has therefore recognised a need to inform stakeholders, to realise the full potential of Earth Observation techniques in both research and commercial operations; hence this guidance report will form a much needed and important step towards establishing the employment of Earth Observation techniques as a matter of ongoing best practice for asset management in all infrastructure projects.

The guidance document will be published in 2021. For more information, please contact satellite@https://middle-east.sixense-group.com

Providing risk management and control throughout the Alaskan Way Viaduct end-of-life cycle

Having suffered earthquake damage, Seattle’s Alaskan Way Viaduct was replaced by the State Route 99 Tunnel. To provide the level of risk control required to carry out this project safely, our local teams installed a total monitoring system for the full 3.2  kilometres of this tunnel beneath the city centre. Four years later, it was joined by another system to monitor demolition of the old viaduct.

Completed on 4 April 1953, the Alaskan Way Viaduct was an elevated double-deck section that carried the State Route 99 above Seattle city centre via the waterfront at Elliott Bay and the city industrial heartland.
The viaduct suffered minor damage in the 2001 Nisqually earthquake, and the following structural inspections persuaded the state and national governments to replace much of the structure with a tunnel beneath the heart of the city.
With a working diameter of 17.5 metres, the world’s largest tunnel boring machine began work on the new State Route 99 tunnel in 2013. The progress made by this super-machine beneath the main landmarks of the city, including Pioneer Square and the Pike Place market, demands an equally impressive risk management and mitigation system.

The highly urbanised environment of this project demanded some very special attention to detail, since existing buildings, engineered structures and utility networks were all exposed to the risks inherent in tunnel excavation.

Controlling these structural and geotechnical risks demanded a wide range of  monitoring solutions, including 37 Cyclops (automated monitoring total stations) installed on building roofs and walls, internal geotechnical instrumentation, underground measurement instruments, real-time monitoring managed directly from the TBM control room, and satellite radar interferometry measurements.

All the data gathered are centralised and managed using the Geoscope decision-support platform. Special attention was paid to converting this data into ready-to-use information for individual project contributors. The scale and environment of this project make its monitoring program the most comprehensive ever implemented in the USA.

As an important member of the Alaskan Way Bored Tunnel team, Sixense has provided outstanding technical support, delivered innovative solutions to complex challenges and maintained an unwavering positive attitude.

David Sowers, Deputy Program Director at WSDOT (Washington State Department of Transportation)

The Rio-Antirrio Bridge in Greece is an exceptionally impressive structure built to endure extreme environmental conditions. Seismic and meteorological risks to its structural integrity must be continually monitored. Its operating concession holder Gefyra has entrusted Sixense with this task for more than 16 years.

From the construction phase onwards, the operating concession holder has needed to monitor the response of the bridge structure to its environment, and validate the assumptions made at the design stage. The ongoing monitoring of the aging structure enables decisions regarding whether the bridge can be reopened or requires maintenance closures following periods of extremely high winds or seismic events.

The Rio-Antirrio Bridge: a structure under the microscope 

EverSense ®, our Structural Health Monitoring System (SHM), was designed and implemented by our teams at the time of construction. Since it opened to traffic in 2004, the 1,000 data acquisition channels of this system have enabled Gefyra to record and characterize the behaviour of the structure and to detect changes in this behaviour, especially after exceptional events such as earthquakes or unusually high winds.

The monitoring system has been regularly maintained and upgraded since implementation. It now incorporates functions that enable real-time traffic management during seismic events or exceptionally high winds.

The EverSense system has made it possible to validate structural design data and coupled with the quality of data generated, has made it possible to allow traffic back safely onto the bridge promptly over 16 years of major environmental events.

The real-time monitoring system implemented by Sixense meant that we could analyse the huge amount of data needed to establish an overview of the structure and receive automated alerts immediately after the earthquake struck. The great advantage of the Sixense system is that it allows us to achieve significant improvements in safety, which is the most important thing from our perspective

Aris Stathopoulos, Structural Maintenance Manager at Gefyra SA/ VINCI Concessions for the Rio-Antirrio Bridge in Greece

Controlling the acoustic impact of a wind farm while minimising the impact on its productivity: that was the challenge faced by our customer Innergex renewable energy.

In response to complaints from local residents regarding noise following commissioning of the wind farm, Innergex decided to take decisive action to ensure good ongoing relations with neighbouring communities as part of its vision to maintain long-term and responsible operational relationships with those living in residential areas around its wind farms. Innergex asked our acoustics experts to develop a methodology specific to this wind farm in order to provide an objective assessment of its acoustic impact in the context of current regulations, and to prepare an effective and optimised noise limitation plan that would deliver guaranteed outcomes.

Our teams then set to work on helping Innergex to resolve this sensitive issue of noise. For this project, our brief was to bring forward a solution that was acceptable to everyone involved, at the same time as meeting Innergex productivity goals for its wind farm. A series of conversations between Innergex and Sixense resulted in the emergence of a completely new study methodology designed to quantify residual noise levels, while maintaining almost full operation of the generators throughout the measurement campaign.

In estimating the overall acoustic impact of the wind farm and establishing a suitable noise reduction plan, our acoustics experts used a range of different techniques, including measurements during full-power operation of the wind turbines and noise decay measurements in close proximity to the turbines to avoid the influence of weather conditions. These measurements made close to the turbines were supplemented by measurements taken at the homes of local residents to ensure perfect calibration of measurements and calculations.

In this way, our engineers were able to develop an optimised noise reduction plan consistent with the current options for programming wind turbine operation. They were also able to contribute to the development of noise reduction options to reduce the intrusion perceived by some local residents. The results achieved following adoption of the noise reduction plan proved fully consistent with the results predicted by the simulations conducted by the acoustics engineers.

The comprehensive nature of this study has given Innergex a high level of control over the acoustic impact of its wind farm and has helped to improve the dialogue and relationship between the wind park and local residents. Based on these successful outcomes, Sixense has applied a similar methodology in a second Innergex wind farm.

We particularly appreciated the professionalism and responsiveness of Sixense, the reliability of the equipment used and the high quality of technical interaction at every stage of these acoustic studies, right through to the submission of reports
Vincent Remillon, Manager France Construction and Operation at Innergex

We have supported Nordex wind farm development projects since 2003 through our involvement in developing the noise component of the environmental impact assessment package for its projects. This long-term partnership has developed throughout our collaboration on more than 50 projects all over france. Now is a great opportunity to look back on this special relationship and the way we operate.

All wind farm projects in France must meet particularly strict regulatory criteria, including the environmental impact study that acts as the basis for consideration of all applications to operate a wind power generating facility. The study is required to demonstrate that the project can be integrated sensitively into its environment, and that the potential impacts of the future wind farm are both managed and controlled.

Noise pollution is a major element of such an impact study. France has some of the most restrictive regulations in the world, requiring wind power projects to comply with a noise emission criterion based on residual noise: the base noise level prior to construction of the project, as measured at the dwellings closest to the future wind farm. A predictive acoustic impact study is then prepared as the basis for estimating the emergence levels (the difference in noise levels with and without wind generators in operation) and providing local authorities and communities with guarantees that the project will comply fully with all applicable rules once it becomes operational.

As acoustic engineers, our priority is to provide an objective and robust study that will enable the wind farm developer to prepare its operating strategy and strike precisely the right balance between power generation and regulatory compliance.

A standard study therefore includes pre-construction residual noise level measurements taken over several weeks, which will serve as the current benchmark level. There then follows the use of a predictive model to forecast the level of noise generated by the future wind turbines. Operating scenarios prepared in consultation with Nordex on the basis of reducing turbine noise levels in different weather conditions are then studied to ensure that the project complies fully with all regulations.

As these projects have advanced, so we have been able to develop our techniques in a number of ways: examples include systematic preliminary visits to all study areas before beginning any campaign to measure the initial noise landscape. The purpose of such visits is to identify the most representative measurement locations and to agree arrangements with local residents before installing our sensors.

The relationship between Nordex and Sixense is much more of a partnership than simply a customer/supplier relationship. The long-term involvement of Sixense in our projects and its excellent understanding of wind farm noise gained from practical experience in the industry mean that Nordex can be certain that the acoustic studies it includes in the impact assessments for its development projects are both robust and comprehensive. The primary goal of the acoustic study is its acceptance by the regulatory authorities, and the feedback we have received from these authorities tells us that the studies produced by Sixense are appreciated not only for their technical and scientific content, but also for their clarity.

As a wind farm developer rather than an operator, it’s important that Nordex obtains the most reliable acoustic measurement results in order to estimate how wind farms should be operated to maximum advantage. So we have to anticipate the possible noise reduction measures to be applied prior to their commissioning. In practice, these noise emission reductions impact the generating output of the project. These issues are relevant, because it is important that the customer ultimately responsible for operating the wind farm has no nasty surprises as a result of underestimating the impacts of the project, at the same time as avoiding the pitfall of devaluing a project by overestimating the risks involved and recommending excessively stringent constraints that will negatively affect the forecast generating output.

From our prospective as a wind turbine manufacturer, the expertise and involvement of Sixense helps us to develop our wind turbines in ways that can take maximum advantage of the operating conditions recommended by Sixense. The issues around the specific impact of wind parks during the particularly sensitive evening period can now be effectively addressed by the wind turbines we produce. In return, our special expertise as a turbine and wind farm developer undoubtedly helps Sixense to continuously improve its knowledge of wind energy technology and related issues.

Quentin Crespel, Acoustics Expert at Nordex France SAS

Using vibration to measure the tension in the cable stays of the MOHAMMED VI bridge in Morocco

At 950 metres in length, the Mohammed VI bridge remains the largest cable-stayed bridge on the continent of Africa. For this type of bridge, cable-stay tension must be adjusted throughout the construction phase to balance the stresses in the bridge deck; in this case, the contractors used hydraulic jacks. Following completion, an additional series of tension measurements were required. Having commissioned the structure, the Chinese contractor Cover-Mbec appointed Sixense to conduct a campaign to measure the tension in each cable-stay using vibration techniques.

Traditionally, hydraulic jacks would be used to take these measurements which entails expensive resources and immobilizes significant sections of the structure for extended periods. The alternate vibration method utilized by Sixense measures the vibration frequency of cable-stays, which provides a direct relationship to their static tension. In practice, accelerometers are attached to the cable-stays and oscillated for a short period.

For this project, the only resources required to perform the vibration measurement were a single work cradle and vibration analysis kit. As a result, only one lane of traffic needed to be closed for the work to be carried out successfully. The tension in all 160 of the bridge’s cable-stays was measured this way, and the report delivered on time.

This is our largest cable-stay tension measurement campaign to date, and the local team was supported by just-in-time data analysis by colleagues in France. This allowed us to optimise the measurement report delivery lead time and meet the deadlines set by our customer”

Quentin Common, Project Manager at Sixense