GRP shells: pipe rehabilitation without open excavation
GRP (Glass Reinforced Polyester) shells are prefabricated structural elements designed for the rehabilitation of large-diameter pipes without open excavation. They restore or improve the hydraulic and structural capacity of existing structures while minimising disruption.
A made-to-measure rehabilitation solution
GRP shells are prefabricated structural elements, made to the shape of the structure. They are installed inside, assembled (mechanical joints or structural bonding), then a grout is injected between the shell and the existing structure. The shell is self-supporting: it is designed to carry all external loads, even if the existing structure is badly deteriorated.
- Made to measure: circular, egg-shaped, modified egg-shaped, horseshoe, rectangular, or from a 3D survey
- For large-section pipes, from DN 600 to over DN 5000, for rehabilitation as well as new structures
- Light and modular: handling and assembly possible in confined spaces
- Excellent chemical resistance (H₂S, industrial wastewater) and very smooth inner surface
- Trenchless works, service life over 50 years according to the manufacturer
- Solution covered by a CSTB technical approval
Principle and installation
Installation overview
| Stage | What you need to know |
|---|---|
| Survey | Inspection and cleaning of the existing structure |
| Design | Case-by-case design: geometry and condition of the structure, soil and traffic loads, grout material |
| Manufacture | Shells made to the exact shape of the structure, with a number of segments suited to the access |
| Installation | Preparing the invert, placing the shells, assembly with mechanical joints or structural bonding, grout injection |
| Acceptance | Final inspection and return to service |
Every rehabilitation is a special case: we help you validate feasibility before any commitment.
For more information, download the brochure.
The benefits at a glance
Chemical resistance
GRP suits aggressive sewer networks: hydrogen sulfide (H₂S) and industrial wastewater.
Made to measure
Circular, egg-shaped, horseshoe, rectangular or based on a 3D survey: the shell matches the existing geometry.
Lightweight
Lightweight prefabricated elements, easy to handle and assemble in confined spaces, including through manholes.
Better flow
A thin wall and a very smooth surface preserve the cross-section and improve flow.
Trenchless
Installed in sections, assembled inside, with grout injection: nuisance minimised.
Service life
Stable material, insensitive to corrosion, service life over 50 years.
Applications
Click an application to see the related solutions.
Accessories and associated parts
A high-performance pipeline is nothing without the right accessories: we help you put together a coherent system.
Annular grouting
Cement grout injected between the shell and the existing structure.
Access manholes
Manhole designed and made to measure, adapted to the existing structure.
Feasibility study
Technical opinion on the feasibility of your rehabilitation.
Your questions about GRP shells
When should I choose a shell rather than sliplining?
When the structure’s section is non-circular (egg-shaped, rectangular, horseshoe…), when access is limited (multi-segment shells, entry through manholes) or when you want to preserve as much hydraulic section as possible. We compare the options with you.
Does the network need to be shut down during the works?
Sliding shells allow sewer lines to be installed with the sewer in service, without over-pumping; after each partial installation, the line can be put back into service. We study this point with you for your site.
Can you give an opinion before a full study is launched?
Yes. Shell sizing is done case by case: we first discuss the geometry and condition of the structure, soil and traffic loads, and the backfill material.
Need personalised support?
Tell us about your project: we help you choose the right solution, size it and prepare the installation. Marc Sadok replies promptly.