During their lifetime, tunnels are subjected to significant deformations mostly due to « burst behaviour » of the ground and the convergence to the tunnel after the excavation.

A set of inflatable circular seals for measuring deformation of a tunnel over a period of time.

As part of the dissertation at LMDC (Laboratory Materials and Durability of Constructions) and under the supervision of Messrs. Sellier and Vidal, Mr. Manzoni developed specific models of tunnel cross sections which were subjected to mechanical stresses in order to study the long term behaviour of tunnels under different conditions, and specifically those subjected to earthquakes. To this end, Pronal was asked to develop and supply a complete system with inflatable circular seals, a pump with a regulator and various tools and accessories. The goal ? Measurements of concrete tunnel deformations caused by ground shifting.

Vérin gonflable torique - maquette

Inflatable circular seals to analyze the behaviour of concrete

During the first test, radial pressure was applied to simulate a homogeneous convergence of the soil. The second test makes it possible to apply selective forces to the concrete model in order to study the effect of uneven thrust. The inflatable circular seal supplied by Pronal for this purpose are inflated to a pressure 35 bar. The tests are running for 6 months at an ambient temperature of 20-40 C and air humidity of 50%.

vérin gonflable torique
Système de gonflage
distribued thrust
High inflation

Data from these tests make it possible to optimize the methods used to calculate the deformation of a tunnel under different conditions. These simulations also make it possible to make recommendations for planning and operation of tunnels.

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