With increase in the dynamic envelope of trains due to the increase of their cross section and speed, the need for widening tunnel cross section of existing tunnels is becoming a necessity. One of the solutions to this problem consists of cutting a fraction of the masonry liner thickness and replacing it with a higher strength, and therefore, a thinner material. In this paper, the case of the widening of the Roches de Condrieu tunnel on the Paris to Marseilles railway line is presented. A maximum of half of the thickness of the existing masonry liner should be removed somewhere between the tunnel crown and the springline. Three-dimensional finite element analysis was used to simulate the effect of this partial cutting of the liner over a limited specified length along the tunnel axis. This study allowed the determination of the maximum length of cutting along the tunnel axis without creating any stability problem for the tunnel section. Once the section cut is reinforced by a higher strength material such as steel fiber reinforced shotcrete, the work resumed with alternating panels
