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A first in FranceThe variable density tunnel boring machine of the Grand Paris Express

Special Feature
10 min
Bouygues Travaux Publics is using two variable density tunnel boring machines on Package T2A of Line 15 South of the future Grand Paris Express rapid transport link. A hybrid between an earth pressure balance and a slurry shield TBM, it is particularly well suited for the excavation of tunnels in complex and varied soils. Spotlight on a hybrid machine.
By Isabelle Godar and Grâce Noyal
  • A. Lining segment erector
    This machine lifts the tunnel lining segments with suction pads and positions them with extreme precision.
  • B. Shield
    The rigid protective structure of the cutterhead that moves forward as the excavation progresses.
  • C. Cutterhead
    As it turns, the disc cutters and scrapers mounted in it cut away the soil.
  • D. Cutterhead motors
  • E. Thrust cylinders
  • F. Lining segments
    Concrete elements assembled to form the tunnel lining rings.
  • G. Screw and hydraulic system for removing excavated material
    The excavated material is removed by an Archimedes screw. After crushing, it is returned to the muck handling system and sent to the slurry separation plant on the surface.
  • H. Backup
    It consists of several trailers that perform logistical functions.
A decision-support tool that optimizes TBM operations and maintenance. Sensors on the disc cutters in the cutterhead supply data that enable the operators to monitor the geological conditions at the tunnel face and optimize excavation and tool maintenance.
The tunnel machine
DIAMETER: 9.84 meters LENGTH: 122 meters
The tunnel lab
August 2016
14 people
To transform ideas coming from the creativity initiatives of Bouygues Travaux Publics (optimization of equipment and logistics, automation, training, big data, new types of tunnels, etc.) into products and services useful in tunnel projects, including Grand Paris Express.

6 innovations


Deployed since September 2016 in all the tunnel projects of Bouygues Travaux Publics, the simulator virtually reproduces the actual geological and operating conditions. Operators now train regularly on the simulator. Bouygues Travaux Publics has made the simulator available to others in the tunnel building sector.


Excavation with a TBM can be more or less difficult depending on the geological conditions. The soil-machine interaction algorithm is the first patented Big Data algorithm of its kind. It compiles all the technical data collected by the TBM and provides the operator with a difficulty rating for the excavation that has just been done to assist him in making decisions about the excavation coming next. The operator can thus know with certainty whether his machine is “straining” or not. Following tests in the Eole project, the SMI will soon be deployed in all the tunneling operations on Line 15.


In use since January 2019, this innovative instrumentation system monitors the structural impact of the worksite on its immediate environment (engineering structures, buildings, streets, railway tracks, etc.). Using data collected by sensors connected to a software program, reliable indicators are calculated, and the information is displayed on a web platform accessible to everyone working in the project. The chief benefit is the ability to predict the work's impact and thereby optimize construction processes. Now employed in the Eole project, this tool will eventually be used at all Bouygues Travaux Publics worksites and sold to companies outside the Group.


The erection of the segments that form the rings of the tunnel lining is a tricky operation. Depending on the operators, it can be performed more or less quickly, taking from 30 minutes to an hour. Atlas makes the job easier and increases productivity. This system invented by teams at Bouygues Travaux Publics and tested in the Eole project installs a tunnel lining ring in 30 minutes, then repeats the cycle automatically. It was developed in a joint project with Capacités, a privately operated subsidiary of the Université de Nantes that specializes in innovative engineering projects. Atlas will also be employed in the construction of the tunnels on Line 15 Sud.


Developed by Bouygues Travaux Publics with support from the Bureau de recherche géologique et minière (BRGM), CaRaCTerre is a tool that quickly determines the pollution levels of excavated material so it can be sent to the appropriate disposal sites. The physical analysis of the concentrations of contaminants in the material is done with a fluorescence X system. The sample examined by X-rays emits waves that reveal the presence (at the atomic level) of any metal trace elements (MTE). Then, using geostatic and geochemical predictive models, the final categorization of the material is done. An analysis can be performed in less than 2 hours, compared with 72 hours when an external laboratory is used. By accelerating the process considerably, this innovation speeds up the management of excavated soil and greatly reduces logistical complications (storage, reloading, waiting). Starting in early 2020, the system will be progressively deployed at Grand Paris Express worksites.


Bouygues Travaux Publics, Objenious (a Bouygues Telecom subsidiary), the e-Lab (the Group R&D unit) and C2S (the Group's digital services company) have teamed up to create the first geolocation tool for tracking excavated materials from worksites. It uses LoRa, a technology employed for the Internet of Things, to ensure that trucks hauling excavated material arrive at the right destination. Now used in all major Bouygues Travaux Publics projects, Ubysol is automatically interfaced with TRex, the web-based material tracking tool of the Société du Grand Paris, to avoid redundant recording of information.

  1. Excavating spoil from worksites
  2. Screening the excavated spoil using CaRaCTerre
    Spoil is screened and sorted at each stage of the process.
  3. Stabilisation of the soil
  4. Loading of excavated spoil onto trucks fitted with Ubysol devices
    Using a NFC tag in a tablet, the sensor collects data on the truck and its load.
  5. Removing the excavated spoil from the worksite
    The truck’s sensor indicates its position in real time to the Ubysol system, which then forwards the information to all other parties concerned (to Société du Grand Paris’ tracking software in particular).
  6. Unloading of spoil
    The sensor ensures that the excavated spoil is unloaded at the correct landfill site.
Photo credits Arnaud Février ; Michel Saemann ; Société du Grand Paris/ Jean-Marie Duthilleul/ Philippe Gazeau.