Experimental investigation of the bearing capacity of deformed segmental tunnel linings strengthened by a special composite structure

Steel plate – concrete composite structure (SPCCS) was recently proposed to strengthen shield tunnels. The steel plate serves as the strengthening material. A combination of connectors and steel-fiber reinforced concrete is employed to establish the bond between the strengthening material and the tunnel lining. A full-scale test was conducted to investigate the mechanical behavior and the bearing capacity of the structure. A comparison of the SPCCS strengthening technique with the epoxy-bonded steel plate (EBSP) strengthening technique was conducted, concerning the distribution of the strain of the steel plate, the joint opening, the bolt strain, slippage, the stripping value, the failure mechanism, and the overall strengthening benefits. The results are shown as follows: for the shield lining, strengthened by the SPCCS technique, the effectiveness of the bond increases, which renders acting of the individual structural components in combination with the tunnel lining more efficient, resulting in the full use of the components of the strengthening device. The failure mode of the strengthened structure is characterized by a high degree of ductility. Compared with EBSP strengthening, the SPCCS strengthening technique results in a reduction of the amount of steel, but in an increase of the bearing capacity and the ductility.