The Museum of Natural History in Paris houses an 18th‑century building which presents collections comprising approximately two and a half million works across 3,000 m² of exhibition halls. By 1988, in the building nearly 100 m long, completely lacking expansion joints, deformations had already been noted related to the settlement of some piles into the foundation soils. The museum management decided from the outset to entrust the organisation CEBTP (Experimental Centre for Research and Study of Building Operation Problems and Public Works) with an investigation into the causes of structural instability. In mid‑December 2004, CEBTP carried out studies which revealed a situation of general soil loosening and destructuring of the soil beneath the foundation. The building occupied by the Palaeontology Gallery, a long structure almost 100 m in length, first showed signs of subsidence as early as the period between the two world wars. In subsequent years, the settlement steadily worsened – until recently, damage appeared on the load‑bearing walls with openings ranging from 10 to 20 mm.

Objectives:
The main objective was to avoid the occurrence of deformations in the pedestrian walkways of the exhibition hall open to the public. The "soft" soil was partially located beneath the Palaeontology Gallery, from which offices occupied by researchers had to be quickly moved, and the damaged sections had to be propped up. In its final report, CEBTP recommended the use of expanding geopolymer injections to consolidate the foundation soils of the building.

Technology applied:
It was decided to use URETEK DEEP INJECTIONS® technology with URETEK® geopolymer injections. Boreholes were made at different levels deep into the foundation, distributed along the foundation strips beneath the exhibition halls. This type of work has a low degree of invasiveness (interference with building structures), with small‑diameter holes: less than 3 cm in diameter. Thus, vibrations are not generated, and the current activity of the building is not disrupted. URETEK® resins, expanding in the foundation soil, cause compaction and improve the resistance and deformability characteristics of the soil, such as cohesion, deformation modulus and compressive strength. The work proceeded in two stages:

Stage 1 – surface compaction: injections are carried out directly under the foundation footing to improve the geomechanical properties of the soil and fill voids at the macroscopic foundation‑soil interface.
Stage 2 – deep strengthening: injections are carried out at several depth levels within the soil volume most subject to loads.

The results obtained confirmed the success of the project through laser monitoring during injections and tests carried out before and after the intervention. After the cracks closed, they did not open again, and the researchers were able to return to their workplaces. All operations were carried out completely independently by URETEK® specialists. The method demonstrates low invasiveness, which requires no preparatory work on site or handling of bulky equipment. The project also demonstrated the skills of URETEK® technicians to work in confined or cramped conditions. A total of 55 linear metres of foundation were treated. All operations, including monitoring and special tests, required 7 working days.