Design and site investigation for the rehabilitation of old railway tunnels

The Portuguese railway network, dating mainly from the last century, has about 120 tunnels. Those tunnels, with different lengths, sections and overburden, cross several types of rocks, ranging from hard to soft ones. The main problems frequently identified, in some of the tunnels mentioned, are related with important water inflows and seepage, lack or insufficient drainage systems, sidewalls and vault deformations, collapse of the masonry support due to excessively opened or weathered joints, the existence of voids behind the lining and finally, rock falls problems in the slope portals. Other situations, which contributed to increase the risk of those tunnels, are the absence of safety cells and monitoring instrumentation. REFER, the entity responsible for the operation and safety of all the railway tunnels is interested in the renovation and rehabilitation of some tunnels. Therefore, several studies were developed in order to identify the risk assessment of their situation, enabling the design and implementation of the most adequate solutions. In this article, we point out the main problems of some old tunnels, with a special emphasis on the site investigations which had to be done without interfering with the normal train circulation, as well as on the design solutions chosen for the complex task of renovating a tunnel. Two case studies are presented, one related with the rehabilitation design and other with the rehabilitation works.