ABSTRACT
The expansion of Lisbon’s Underground network through the Yellow and Green lines extension project is taking place in a densely urbanized area of Santos and Cais do Sodré. The area, close to the Tagus River, combines challenging ground conditions and a large diversity of vulnerable assets, including heritage listed buildings, residential buildings and major utilities companies’ assets. The project comprises the construction of the new Santos station and adjacent tunnels using the Conventional Method. The construction works will employ a sequential excavation method through poor ground conditions and low ground cover, including sections with less than one diameter of ground cover between the tunnels and the surface. In order to reduce the risk of damage to the buildings located in the zone of influence of the excavation works, a comprehensive damage assessment study was carried out in the initial stage of the project to assist the design of the tunnel primary lining and cut & cover retaining walls. This article will present the key challenges faced by the design team and the adopted solutions to reduce the risk of damaging the existing assets.
