Seismic Pit Excavation
The Tokamak Complex Seismic Isolation Pit: 130 metres long, 90 metres wide and 17 metres deep. (March 2011)
The quality of the rock substrata on the 42-hectare ITER platform has determined the exact location of the 440,000-tonne Tokamak Complex, the heart of the ITER scientific installation.
The Tokamak Complex will be contained within a seismic isolation pit—a 17-metre-deep, 90 x 130 metre hollow in the ITER platform excavated to house the concrete basemat, retaining walls, and seismic pads that will protect the buildings and equipment in the case of a seismic event.
The excavation works to remove 210,000 cubic metres of soil and rock for the seismic isolation pit began in August 2010. After excavating down to 17 metres, engineers conducted sample drilling and radar surveys to establish a detailed map of the underlying bedrock. Several small voids ("karsts") were detected and explored, widened, and filled with concrete. Engineers used survey data to verify the assumptions used for Tokamak Complex design, before the establishment of the final structural design.
The final excavation phase for the seismic isolation pit involved milling the rock in order to achieve a perfectly flat surface on which to lay a first "blinding" layer of concrete. Construction of the ground support structure for the Tokamak Complex—basemat, retaining walls, seismic columns and pads, and final B2 basemat slab—began in August 2011 and was completed in August 2014.
Excavation facts:
- Excavation works: August 2010-April 2011
- Depth of the Seismic Pit: 17 metres
- Dimensions of the Seismic Pit: 90 x 130 metres
- Volume of rock and soil removed: 210,000 m³
- Mass of the Tokamak Complex: 440,000 tonnes (including the 23,000-tonne ITER Tokamak)
Photo Gallery
Tokamak Complex configuration model
2023-09-15 - Big city lights or fusion facility? This illustration shows the openings and penetrations implemented in the Tokamak Complex Buildings Configuration Model. Image credit: ITER Organization (2010)
A thin layer of blinding concrete
2011-05-27 - A five-ten centimetre layer of "blinding concrete" will create a smooth and flat work surface. Photo: AIF
The Hot Cell Facility will be adjacent to the Tokamak Complex
2011-05-27 - The Tokamak Complex Seismic Pit to the left, 17 metres deep, and to the right, the smaller and more shallow area that will house the foundations of the Hot Cell Facility. Photo: AIF
Drilling and clearing
2011-05-12 - Work continues to clear, clean, and fill the irregularities in the rock floor of the Seismic Pit. In the background—the first building on the ITER platform.
Tower cranes in place
2011-05-05 - Tower cranes at each of the four corners of the Seismic Isolation Pit will be used to lower the tons of steel rebar needed for the reinforced foundations of the Tokamak Complex.
A last bit of blasting
2011-05-05 - Final "profile" blasting is carried out in May on the contours of the Tokamak Complex Seismic Isolation Pit.
Dealing with geological particularities
2011-04-29 - Karsts, or small cracks in the geological surface of the Seismic Pit, are cleaned, inspected, enlarged, and filled with concrete.
The Seismic Pit in April 2011
2011-04-29 - Work continues on the floor of the Seismic Pit to explore and widen karsts - or fissures - in the first five metres of rock.
Green banks below
2011-04-28 - The green banks of the ITER platform, planted last year with over 3.5 tonnes of seeds, stand out against a grey April sky. A lone digger works to create a staircase to lead from the contractors' area below to the worksites on the platform.
The ITER platform—looking northeast
2011-04-17 - Looking northeast over the Tokamak Complex Seismic Isolation Pit in April. Photo: Altivue/Spie Batignolles
Blasting for the Hot Cell Facility
2011-04-17 - Less profound than the main work site, the square area that abuts the Tokamak Complex Seismic Isolation Pit to the north is reserved for the foundations of the ITER Hot Cell Facility. Final trim blasting will be carried out in May 2011 to finalize the perimeters of this area. Photo: Altivue/Spie Batignolles
The double batching plant seen from above
2011-04-17 - The on-site concrete batching plant, seen from above. Photo: Altivue/Spie Batignolles
Concrete produced on site
2011-04-13 - To produce the estimated 250,000 m³ of concrete necessary for the construction of the ITER facilities, a specially dedicated concrete batching plant was built on site. Here: the two mixing machines, each with four tanks. Photo: AIF
As heavy as the Empire State Building
2011-03-10 - Some 360,000 tonnes of foundation and building will rest on the bottom of the Seismic Isolation Pit; 360,000 tonnes is the weight of New York's Empire State Building. Photo: F4E
Making sure the level surface is perfect
2011-03-10 - On the clean-swept floor of the Seismic Pit, land surveyors' instruments are used to verify the exactness of the levelling operations. Photo: F4E
Steel mesh for safety
2011-03-10 - Workers secure steel mesh for the stabilization of rock faces. Photo: F4E
Safety mesh installed along the rock face
2011-03-10 - Workers rappel down the walls of the Seismic Isolation Pit to install wire mesh along the rock face as a protective measure for those working below. The horizontal rock surface of the 90 x 130 metre Tokamak Complex Seismic Isolation Pit is as smooth as a billiard table. Photo: F4E
Checking the geometry of the excavation
2011-03-10 - Laser and land surveyor rods are used to measure the surface levelling before foundation work begins. The technique of microgravity is used to measure gravity variations in order to determine rock properties. Photo: F4E
ITER will be a busy place
2011-03-03 - At the peak of ITER construction in 2014-2015, 5,000 people are expected on the ITER site, up from 1,400 in 2011. The projected rise is due to a sharp increase in the number of construction workers on the platform.
The future home of the ITER Tokamak
2011-02-24 - The heavy excavation works for the future Tokamak Complex were completed in four months. Photo: F4E
Investigating the rock substrata
2011-02-24 - By way of radar mapping and the boring of more than 500 holes, geological surveys provided a detailed map of the substratum. Some voids were detected, the largest being a few cubic meters in volume; these small voids, or "karsts" must now be filled with concrete. Photo: F4E
Next step: the blinding layer of concrete
2011-02-24 - Precise measuring instruments are used to create the level surface required for the anti-seismic installation of the Tokamak Complex. Next step: the pouring of a thin, "blinding" layer of concrete to have a perfectly smooth work surface. Photo: F4E
February 2011
2011-02-24 - The Tokamak Complex Seismic Isolation Pit in February 2011. Photo: F4E
Seventeen metres below the surface of the platform
2011-02-24 - The final excavation phase now involves "milling" the rock in order to achieve a perfectly flat surface, on which to commence the construction of the lower basemat. Photo: F4E
Next come the ground surveys
2011-02-24 - The floor of the Seismic Pit is 17 metres below the level of the platform. Ground surveys will provide information about the underlying bedrock in order to verify the assumptions used for the design of the Tokamak Complex. Photo: F4E
Mesh protection
2011-02-24 - The rock face is draped with protective steel mesh as the last diggers, scrapers and dumpers prepare the Seismic Pit for the concrete pourers to move in. Photo: F4E
The southwest rim
2011-02-24 - Seen from the southwest rim: the 87 m x 123.6 m hollow in the ITER platform that will house the future ITER Tokamak. Photo: F4E
The last sweeping operations
2011-02-24 - Mesh is installed in the background as the last gravel is swept from the floor of the Tokamak Complex Seismic Isolation Pit. Photo: F4E
Milling the surface
2011-02-24 - The Tokamak Excavation area is readied for the pouring of a thin layer of "blinding concrete" that will create the clean and flat work surface upon which to create the 1.5 metre-thick basemat. Photo: F4E
PF Facility in the distance
2011-02-10 - The walls and roof trusses of the Poloidal Field Coils Winding Facility go up in the distance, blurred by the dust from the excavation site. Photo: F4E
The rocky slope ...
2011-02-10 - The access road for construction vehicles into the Tokamak Complex Seismic Isolation Pit. Photo: F4E
Planing machine in action
2011-02-10 - The planing machine in action on the floor of the Seismic Isolation Pit. Photo: F4E
210,000 cubic metres of material
2011-02-10 - Trucks move back and forth continuously between the excavation site and a rubble storage area located to the east of the ITER platform. Storing the material on site limits the amount of construction traffic on the roads closest to ITER. Photo: F4E
Officially 17 metres deep
2011-02-07 - Blasting operations are over: trucks work on the floor of the Tokamak Complex Seismic Isolation Pit to remove rubble from the area. Photo: F4E
Drilling holes every four to five metres
2011-02-07 - Boring holes up to five metres deep to develop a detailed "picture" of the rock substrata of Seismic Pit floor. Photo: F4E
An Arc de Triomphe in Provence
2011-02-07 - The Tokamak Building will sit 13 metres below ground and 60 metres above ground. 60 metres is the approximate height of the Arc de Triomphe in Paris. Photo: F4E
Boring and drilling activities continue
2011-02-07 - Drilling is carried out every 4 to 5 metres and up to 5 metres deep in order to explore the rock surface of the Seismic Pit. Photo: F4E
How many tons??!
2011-02-07 - The Tokamak Seismic Isolation Pit will house the anti-seismic foundations of the future Tokamak Complex. Some 360,000 tonnes will rest on the bottom of this Pit, including the foundations, the ITER Tokamak, and Complex edifice. Photo: F4E
The Hot Cell Facility: The Tokamak Complex's closest neighbour
2011-02-07 - In the foreground: the location of the future Hot Cell Facility. Trim blasting for this area will be carried out in April 2011. Photo: F4E
A steady supply of concrete
2011-02-07 - The concrete batching plant seen in the distance will supply the 150,000 tonnes of concrete necessary for the ground support structure of the Tokamak Complex (foundations and retaining wall). Photo: F4E
Exploring the rock surface
2011-02-07 - Rubble is removed and fissures, faults and karsts on the rock surface explored. With radar mapping and the boring of more than 500 holes, geological surveys provided a detailed map of the substratum. Photo: F4E
360,000 tonnes of building
2011-02-07 - The quality of the rock substrata on the 42-hectare ITER platform has determined the exact location of the 360,000-tonne Tokamak Complex. In the area of the Tokamak Building, the soil bearing capacity will be at least 100 tonnes per square metre. Photo: F4E
Tons and tons of rock
2010-12-21 - Excavating to 17 metres requires the removal of an estimated 210,000 cubic metres of rock and soil from the ITER platform—a feat that was accomplished in four months. Photo: F4E
Two projects advancing
2010-12-21 - Across the excavation worksite, the first concrete pillars of the Poloidal Field Coils Winding Facility are seen in the distance. Photo: F4E
Seen from above
2010-12-19 - The Tokamak Complex excavation worksite seen from the sky in December 2010. Photo: Altivue/AIF
First phase of excavation is over
2010-12-10 - The 90 m x 130 m Seismic Pit is measured at 298.65 m above sea level; the ultimate excavation depth of 17 m is almost achieved.
As the year ends ...
2010-12-09 - In the late afternoon sunshine in December, the blasting marks are clearly visible along the face of the Seismic Isolation Pit.
Soil and rock excavated
2010-10-08 - Over the course of four months, 210,000 cubic metres of soil and rock are excavated from the ITER platform to form the Tokamak Complex Seismic Isolation Pit.
Digging and blasting down to 17 metres
2010-10-08 - Ongoing rock blasting and excavation activities on the ITER platform to create the Tokamak Complex Seismic Isolation Pit.
ITER seen from the sky as construction is launched
2010-09-15 - This aerial photo, taken in September 2010, shows the ITER site as the digging begins for the Tokamak Complex. Photo: Altivue/AIF
The Tokamak will stand here
2009-03-31 - On the level ITER platform, the quality of the rock substrata has determined the exact location of the future 360,000-tonne Tokamak Complex, where physics experiments will be conducted. Photo: Altivue/AIF
The 42-hectare ITER platform in Cadarache, France
2009-01-29 - From 2007-2009, work on the ITER site work was divided into two phases: the clearing of 90 hectares; and the levelling of a vast platform to house the buildings and facilites of the ITER scientific experiments. Photo: Altivue/AIF
Clearing works are finished
2008-11-02 - The ITER site seen from above in February 2008. Photo: AIF VDC
Replanting the slopes
2008-01-10 - The slopes of the ITER platform replanted with local seeds ... some 3.5 tonnes of seed in all. Photo: AIF AM
The Tokamak is in yellow
2006-05-05 - Rising 60 metres above ground, the Tokamak Complex will house a complex array of plant systems to support the ITER Tokamak. Image credit: ITER Organization
Isometric view
2006-05-05 - An isometric view of the ITER plant systems in Level B2, B2M, B1 and L1 of the Tokamak Complex. Image credit: ITER Organization
Building cutaways
2006-05-05 - From left to right, the Cleaning Facility, the Assembly Building (where two subassembly tools stand ready to suspend the vacuum vessel sectors) and the Tokamak Building. Image credit: ITER Organization
X marks the spot
2006-05-05 - A flagpole is planted to mark the future centre of the ITER Tokamak, as site clearing works begins in 2006.
13 metres below ground
2006-05-05 - A vertical section of the future Tokamak Complex showing the ITER Tokamak nestled 13 metres below ground within the thick foundations of the Seismic Isolation Pit, now under construction. Image credit: ITER Organization