Fondazioni e opere speciali nel sottosuolo

1478 – Napoli cimitero Poggioreale

LINEA 1 OF THE NAPLES METROPOLITAN SPA strada CDN - CAPODICHINO - Works of cavity filling and recompression of uneven ground in the area of the Monumental Cemetery of Poggioreale

M.N. Metropolitana di Napoli S.p.A.

Period of Execution:
January 2023

Works Amount:
€ 1.993.778,20


The survey campaign, carried out specifically within and around the cemetery area, revealed the presence of loose soils and sometimes voids in the subsoil. It was therefore necessary to design an intervention to secure the area.
The technology used is that of soil consolidation using cement injection. The consolidation work was designed in two distinct stages:

  • Step 1 – gravity injection to fill the voids possibly present in thesubsoil;
  • Step 2 – pressure injection for recompression of loose soil levels.

Step 1
Aimed at filling the voids possibly present in the subsoil, a network of injection holes was planned within the cemetery area, arranged on a square mesh with hole bottom 2.50 x 2.50 m.
The boreholes were drilled from ground level, within the cemetery area, with the most appropriate geometries compatible with the interference with the funeral buildings on the surface and their basement floors.
Given the extremely limited space available between the various funerary buildings, a small drilling machine, a Comacchio MC 400, was used.
For each injection hole, after drilling was completed, a high-expansion cementitious mixture was injected through the same battery of drill rods.

Step 2
For this type of soil consolidation, the technique of repeated and selective injections through
manchettes (TAMs) was planned.
Once the design depth was reached by drilling, the TAMs were installed inside the temporary lining, the temporary lining was formed and extracted, and the lining was then topped up with additional mixture.

The sheathing mixture, consisting of cement, bentonite and water. After the sheath mixture had cured (not earlier than 72 hours), the design cement mixture was injected under pressure.
Injection was carried out by the selective and repeated procedure: double packer placed on each manchettes valve.
The injection parameters were as follows:

  • maximum volume = 300 l/valv.
  • rejection pressure:
    • 12 bar (prof. ≥ 10 m)
    • 8 bar (3 ≤ prof. < 10 m)
    • 5 bar (prof. < 3 m)