French term (edited): Dallage sur terre plein

Un dallage est un ouvrage de grandes dimensions, généralement en béton ou béton armé, qui repose uniformément sur le sol.
https://fr.wikipedia.org/wiki/Dallage_(construction)

Dans le domaine de la construction, le dallage d'un sol est son recouvrement par des dalles jointives, c'est-à-dire des plaques suffisamment épaisses pour ne pas se fracturer lors du passage de personnes ou de véhicules.
https://fr.wikipedia.org/wiki/Dallage

Un terreplein1 ou terre-plein est un ensemble de couches talutées servant à l'assise d'une monodalle, d'un immeuble, d'un dallage ou d'une infrastructure de transport, généralement conçu pour supporter un poids important, des vibrations et incorporant divers systèmes d'évacuation (au minimum via une pente suffisante (ex : >2cm/m pour les eaux de vannes).
https://fr.wikipedia.org/wiki/Terre-plein_(architecture)

Français Anglais
dallage nm (fait de poser des dalles) flagging, paving n; flagstone laying, pavement laying, cobblestone laying n
dallage nm (sol fait avec des dalles) (outside) paving n; (inside) tiling n
https://www.wordreference.com/fren/dallage

paving | An outdoor hard surface of engineering bricks, flags, floor tiles, pavers, quarries, radial setts, slabs, etc., usually laid on sand bedding
paving slab, precast slab | A large slab of precast concrete or cast stone sometimes made with hard granite chippings, suitable for pedestrian areas
flag, flagstone | A slab of precast concrete, or cast or natural stone, used for paving footways, for landscape hard surfaces, or as a floor finish.
slab-on-grade (USA) | a ground slab
ground slab (USA slab-on-grade) | A concrete slab supported by the ground, unlike a suspended slab. It can be on fill, which should not exceed 600mm in thickness. …
sand bedding | A layer of sand, usually 50 mm thick, placed on an excavated formation, to provide a flat surface for ground slab.
(The Penguin Dictionary of Building)

One area of innovation relates to improvements in the bedding support under precast concrete panels. This Tech Brief describes the technical considerations for bedding support and current bedding support practices for PCP systems.
https://www.researchgate.net/publication/286246097_Precast_C...

In the paving block pavement, it normally consists of the following main elements: sub-base, sand bedding and paving blocks. Sub-base is the main structural element to take up traffic load and spread it into larger area so that the traffic stress is small enough for subgrade to sustain. Sand bedding is used for providing correct line and level for paving blocks to lie on. To achieve this, screeding of bedding layer is implemented so that the paving blocks could be laid directly on it without the need of further leveling.
https://www.engineeringcivil.com/can-the-sand-bedding-be-omi...

Concrete block pavement is used as a modern pavement type owing to its economic benefits.
:
The factors that affect LTE are bedding sand (type, grading, and thickness), joint sand (type and grading), and concrete block (shape and pattern). Therefore, the optimal design for concrete block pavements can be achieved by analyzing each factor.
https://www.researchgate.net/publication/355807288_Performan...

Illinois Concrete Or Cement Work--floors, Driveways, Yards, Or Sidewalks & Drivers Class
Applies to ground supported paving other than paving that is performed on streets, roads or airport runways or warming apron.
https://www.insurancexdate.com/class/IL/DwGN/concrete-or-cem...

5221 Concrete or Cement Work (Curbs, Gutters, Driveways, Walls, Parking Lots or Sidewalks) & Drivers
NATIONAL SCOPE: Code 5221 is used for any type of ground‐supported paving other than paving that is performed on streets, roads.
https://www.oregon.gov/odot/Construction/Documents/ClassCode...

Proposal:
Paving on (sand) bedding, or
Ground-supported paving

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Note added at 1 day 23 hrs (2021-11-06 12:14:54 GMT)
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Additional sources:

dallage / paving with flagstones o. slab o. tiles | (tôle) / flooring plate | (bâtim) / stone floor
dalle / (bâtim) / plate | ~ / pierre plate, plate of stone, broad stone, slag, flag | ~ en béton / concrete slab | … ~ de pavage / paving o. floor tile
(Dictionnaire Général de la Technique Industrielle)

pave / paver | ~ with flags / daller, carreler, poser des carreaux
paved floor / pavement, pavé, aire pavée | ~ road / pavé
pavement / pavé, pavage | (GB) / trottoir | (US) / chaussée | | (road) corps de chaussée | ~ plate o. slab o. tile (GB) / dalle de trottoir
paving / pavement, pavé, aire pavé | … ~ flag / dalle, plaque
~ with flags o. slabstones o. tile /couverture à dalles, carrelage, dallage
(Comprehensive Dictionary of Engineering and Technology)

Note : « dallage » s not limited to road construction or house building, but to all stone setting work from concrete slabs to paving sidewalks. The context is likely to be the construction of buildings, where concrete slabs (concrete pavings) are often used.

We can replace paving by slabs, as this is a synonym.

2nd Proposal:
slabs on (sand) bedding, or
Ground-supported slabs

It's been a while since you posted your question so you may well have found an answer by now, but for the benefit of future searches, here is my contribution.

Looking at the surrounding elements, this has to be "dallage sur terre PLEINE". While the term is not exactly standard, it obviously stands in opposition to the different types of "plancher" (suspended) mentioned, and as a structural element it is necessarily part of the building, which eliminates the second definition of 'dallage" below pertaining to external works (parking areas, driveways, etc.)

[B.A.P.] [this stands for béton auto-plaçant, self-compacting concrete, but prior to the development of this kind of concrete, ground slabs were (and still are) built with conventional concretes] Dalle de béton plus ou moins armé selon l'utilisation, S'APPUYANT DE MANIÈRE CONTINUE SUR LE SOL par l'intermédiaire d'une forme réalisée avec des granulats compactés.
[Rev. - V.R.D.] Revêtement de sol dur, constitué de dalles (pierre, céramique, etc.), de pavés, etc. - Pose d'un tel revêtement.
https://www.editions-eyrolles.com/Dico-BTP/definition.html?i...

So we're looking at the first definition above, or as reiterated below!
"Un dallage est un OUVRAGE PLAN EN BÉTON DE GRANDES DIMENSIONS par rapport à son épaisseur, éventuellement découpé par des joints, qui REPOSE UNIFORMÉMENT SUR SON SUPPORT, éventuellement par l’intermédiaire d’une interface."
https://www.adets.fr/images/easyblog_articles/44/Chapitre-6-...

This corresponds to the English "groundslab" (also, less commonly, "ground-bearing slab"; "grade slab" in India). Other terms are "slab on grade" [US], also "slab on ground" which are closer to the French, but they are strictly the same as "groundslab"

"According to the Building dictionary this is a concrete slab supported by the ground, unlike a suspended slab. It can be on fill, which should not exceed 600 mm in thickness. The formation may be shaped for thickenings and covered with hardcore and sand bedding or a layer of blinding concrete. It may also need a sheet plastics damp-proof membrane depending on site conditions and building occupancy. Large areas of ground slab are cast in alternate bays."
https://www.proz.com/kudoz/english/construction-civil-engine...