Tunnelling in urban areas: the use of lateral walls to protect ancient buildings
Tutor / director / evaluatorLedesma Villalba, Alberto
Document typeMinor thesis
Rights accessOpen Access
Famous buildings of historical significance tend to occur in large, old cities such as London, Athens, Rome, Paris and Moscow, which also happen to be cities with some of the oldest and largest metro systems in the world. Metro stations tend to be placed near these monuments in order to attract scores of tourists. Various additional factors, such as traditional construction techniques and shallow foundations, conspire to make ancient buildings much more sensitive to ground subsidence than their modern counterparts. Furthermore, it is essential to make sure ancient buildings remain undamaged, as they are very much in the public eye and any damage sustained will have huge effects on the public opinion of the project. This project investigates the various aspects of constructing lateral walls to protect ancient buildings, the various types of lateral walls, their construction methodology and their design methodology. As background to the lateral wall discussion, this project gives a brief overview of the various tunnelling techniques that exist, the various damage classifications and the considerations specific to boring tunnels near ancient buildings. Finally, this project will focus on the AVE high-speed train line tunnel that is currently being constructed near the foundations of The Sagrada Familia, Barcelona’s iconic cathedral built by the famous Catalan architect, Antoni Gaudí. The scope of this project will primarily concentrate on the piled wall screen that has been built in order to protect the priceless Cathedral. The 2D finite element package Plaxis was used to perform a finite element analysis of the Sagrada Familia, the piled wall and the surrounding area. A comparison was made between five different cases: A piled wall with a concrete block at the head and an area of consolidated soil (the adopted solution); a wall with no concrete block but with consolidated soil; a wall with a concrete block but no consolidated soil; a wall with no concrete block or consolidated soil; and finally, no wall at all. The results show that the wall reduces surface deformations of the Sagrada Familia. The presence of the wall reduces the maximum vertical deformation by 41%. However, the maximum horizontal deformation was unchanged, although its location moved 10m away from the tunnel. With the wall, all points were shifted to the bottom left on the Boscardin and Cording graph, well within the negligible damage range, whereas without it, one point lay within the very slight damage range. However, the concrete block and/or consolidated soil offer little to no reduction in maximum vertical or horizontal deformation. Additionally, their incorporation does not affect the points on the Boscardin and Cording graph. A comparison between the measurements of the FEM analysis and measurements taken in practice conclude that the tunnel, together with the protective measures taken, poses minimal risk to the structural integrity of the Sagrada Familia.