STEEL FIBER REINFORCED CONCRETE FOR THE BARCELONA METRO LINE 9 TUNNEL LINING

摘要

This work presents the experimental studies carried out for evaluating the possible application of steel fiber reinforced concrete, without any conventional reinforcement, in the precast/prefabricated tunnel lining segments of the new Metro Line 9 under construction in Barcelona. The TBM-excavated tunnel has a diameter of about 12 m and a length of more than 40 km, and is located 30 to 70 m below the surface. According to the original design project, the reinforced concrete segments are of steel fiber reinforced concrete, with a high quantity of conventional reinforcement. However, the mechanical contribution of the fibers is not taken into account and the fibers are incorporated only to control the cracking that could occur during handling and placing of the segments. Here, an alternative solution was evaluated without any conventional reinforcement through the characterization of the material properties, from which a specific type of steel fiber was chosen from five different possibilities, and structural scale tests to study the behavior under critical loading conditions: flexure, concentrated in-plane loads, and possible stress concentrations in the joint between segments of the same ring. It was concluded that segments reinforced with 60 kg/m~3 of appropriate steel fibers could satisfy the requirements of the project, without necessitating any conventional reinforcement.