Design of steel fiber reinforced concrete segment with curved radial joints

Mumbai Metro Line 3 is major underground project with 33.5 km of twin tunnels and 27 stations with estimated cost of 2.8 million Euros. The tunnels are being constructed with tunnel boring machines (TBMs). Segments for this project have curved radial joints to minimize crushing of concrete during ovalisation and convergence of segmental lining. Curved radial joints have lower contact widths between segments resulting into higher stresses around area of contact. The existing guidelines do not provide a design approach for curved radial-joints of steel fiber reinforced concrete (SFRC) segments. This paper discusses an approach to design radial-joints for SFRC segments by combining International Tunnelling Association (ITA) guidelines and Roark’s-design formulas. The parameters considered for design are included and verified by test results. Likely future-improvement in this design approach is optimizing amount of reinforcement required for radial joints by considering tensile capacity of SFRC matrix.