Protecting sensitive constructions from tunnelling: the case of World Heritage buildings in Barcelona

Construction of the tunnel for the high-speed Madrid–Barcelona–France railway link across central Barcelona became a major technical and social challenge due to the impact of the tunnel on nearby historic buildings (two of them, the Sagrada Familia basilica and Casa Milà, being United Nations Educational, Scientific and Cultural Organization (Unesco) World Heritage structures). Protection of sensitive buildings from tunnelling-induced movements relied on the construction of a stiff pile wall, separating the tunnel from historic sites. This paper first presents a simplified procedure to analyse the wall–tunnel interaction in a straightforward manner. The main features of the tunnel, excavated by means of an earth pressure balance machine in tertiary clays and sands below the water table, are then described. Details of the design of the wall that was finally built are presented. Issues that were particularly important include the groundwater flow constraints and the use of small-strain soil stiffness properties to obtain realistic settlements. General criteria to design the protection wall are also presented. The good performance of the wall resulted in negligible tunnelling impact on the sensitive structures. The measured and predicted displacements are compared, suggesting that this type of solution is adequate to protect historic structures from tunnelling.