{"id":836403,"date":"2026-06-22T16:29:03","date_gmt":"2026-06-22T14:29:03","guid":{"rendered":"https:\/\/www.nidaplast.com\/realisations\/remblai-allege-zone-marecageuse-ametzondo-bayonne\/"},"modified":"2026-06-24T15:44:10","modified_gmt":"2026-06-24T13:44:10","slug":"lightweight-fill-marshy-ground-ametzondo-bayonne","status":"publish","type":"realisations","link":"https:\/\/www.nidaplast.com\/en\/case-studies\/remblai-allege-zone-marecageuse-ametzondo-bayonne\/","title":{"rendered":"Lightweight Fill on Marshy Ground: Building a Subsidence-Free Access Road at Ametzondo, Bayonne"},"content":{"rendered":"

At Ametzondo, Bayonne (Pyr\u00e9n\u00e9es-Atlantiques, France), a new commercial development required an access road across entirely waterlogged marshy ground.<\/p>\n

The key challenge: prevent ground subsidence<\/strong> while supporting frequent vehicle traffic.<\/p>\n

Conventional granular fill<\/strong> on this soft, high water table site would have caused inevitable settlement and structural distress.<\/p>\n

The solution: 780 m\u00b3 of Nidaplast RA500 cellular lightweight fill<\/strong> \u2014 a hydraulically transparent fill<\/strong> that eliminates buoyancy forces and dramatically reduces the load on soft compressible ground<\/strong>.<\/p>\n

2015<\/p>\n

year of construction<\/p>\n

780 m3<\/p>\n

lightweight fill<\/p>\n

RA500<\/p>\n

marshy ground<\/font><\/p>\n

Ametzondo, Bayonne: Building a Road on Waterlogged Marshy Ground with a Fluctuating Water Table<\/h2>\n

The Ametzondo zone on the outskirts of Bayonne is naturally marshy ground subject to water table fluctuations. Constructing a load-bearing access road on this type of site presents two interrelated problems: the weight of conventional fill would cause progressive ground consolidation and settlement; and the presence of fluctuating groundwater rules out EPS geofoam<\/strong>, which generates buoyancy forces when submerged and loses its mechanical stability in saturated ground.<\/p>\n

Design engineer Egis France and contractor Guintoli selected Nidaplast RA500 as the solution meeting both constraints simultaneously: sufficiently lightweight to limit settlement, and open-cell to eliminate buoyancy forces entirely.<\/p>\n

Why Nidaplast RA500 Lightweight Fill Is the Right Solution for Marshy and Wetland Ground<\/h2>\n

40\u00d7 lighter than conventional fill \u2014 settlement controlled at source<\/strong><\/p>\n

At approximately 40\u201344 kg\/m\u00b3, Nidaplast RA500 reduces the load applied to the marshy ground<\/strong> in direct proportion to the depth of substitution.<\/p>\n

Where conventional granular fill<\/strong> would exert 1,700\u20131,900 kg\/m\u00b3 of vertical stress \u2014 causing unacceptable settlement \u2014 the cellular lightweight fill<\/strong> transmits only a fraction of that load, compatible with the bearing capacity of soft high water table ground.<\/p>\n

Hydraulically Transparent Fill: Zero Buoyancy, No EPS Geofoam Risk<\/strong><\/p>\n

The open-cell hexagonal structure of Nidaplast RA allows water to circulate freely through the fill.<\/p>\n

When the water table rises \u2014 a frequent occurrence on marshy ground \u2014 the fill generates no buoyancy force whatsoever: no uplift, no displacement, no mechanical property loss.<\/p>\n

Nidaplast RA is the only lightweight fill<\/strong> qualifying as a hydraulically transparent fill<\/strong>, a property exclusive to open-cell polypropylene honeycomb structures.<\/p>\n

This is the decisive advantage over EPS geofoam<\/strong> or any closed-cell lightweight fill alternative<\/strong> in a high water table or flood zone context.<\/p>\n

No prior ground treatment required<\/strong><\/p>\n

The cellular lightweight fill<\/strong> is placed directly on the existing marshy ground without prior ground improvement \u2014 no stone columns, no soil replacement, no geomembrane.<\/p>\n

Blocks are manually handled, which is critical on waterlogged terrain where heavy plant access is limited.<\/p>\n

\"Nidaplast

Nidaplast RA<\/p>

Nidaplast RA lightweight embankments<\/strong> are extremely light and resistant. These honeycomb structures are the recommended solution for constructing landscape embankments, road embankments, or building embankments.<\/p>View product sheet<\/a><\/div><\/div>\n

Lightweight Fill Installation on Marshy Ground at Ametzondo: Construction Sequence<\/h3>\n

1. Block delivery and inspection:<\/strong> <\/p>\n

Nidaplast RA500 blocks received and checked on site.<\/p>\n

2. Anti-contamination geotextile:<\/strong><\/p>\n

The geotextile separator is placed first, isolating the lightweight fill from the marshy foundation ground and preventing fines migration into the cellular structure.<\/p>\n

3. Block installation in successive layers:<\/strong><\/p>\n

Blocks placed with cross-jointed coursing to maximise inter-block stability.<\/p>\n

4. On-site cutting:<\/strong><\/p>\n

Blocks cut with a chainsaw to match the road access geometry.<\/p>\n

5. Geotextile wrapping:<\/strong><\/p>\n

The geotextile is closed over the top face and lateral faces of the fill mass.<\/p>\n

6. Overlying fill and road structure:
<\/strong><\/p>\n

Compacted fill and road pavement structure placed above the lightweight fill mass.<\/p>\n

Results: A Stable Access Road on Marshy Ground, Open to Regular Vehicle Traffic<\/h2>\n